Pushing the Boundaries of Space · 31 invited conference presentations, and contributed to 166 other presentations. The research topics include under-standing the ring current, diffuse

Crosslink®

The Aerospace Corporation magazine of advances in aerospace technology

Fall 2014

Pushing the Boundaries of Space

CrosslinkFall 2014 Vol. 15 No. 1

4 Technology and Innovation: The Key to New System Development

Sherrie L. Zacharius

A technology-focused culture of innovation is essential for the national security space enterprise to succeed.

6 Think Big, Fly Small

Charles L. Gustafson and Siegfried W. Janson

The increasing popularity and functionality of small satellites has helped them move beyond technology demonstration and into the realm of commercial and governmental applications.

12 Internal Research and Development Spurs Advancements and Fills Technology Gaps

T. Paul O’Brien

Aerospace internal research has led to real-world components that vastly miniaturize space environment sensors.

18 2025 and Beyond: The Next Generation of Protected Tactical Communications

Jo-Chieh Chuang, Joseph Han, and Bomey Yang

Developing affordable, protected, and interoperable satellite communications systems are goals of tomorrow’s space and ground architectures.

26 Applying Systems Engineering to Manage U.S. Nuclear Capabilities

Matthew J. Hart, James D. Johansen, and Mark J. Rokey

The Aerospace Corporation’s expertise in program systems engineer-ing and integration is being applied to nuclear programs for the National Nuclear Security Administration.

IN THIS ISSUE

Departments

2 PROFILEMargaret Chen

30 RESEARCH HORIZONS

36 BOOKMARKS

56 CONTRIBUTORS

60 BACK PAGE

Copyright © 2014 The Aerospace Corporation. All rights re-served. Permission to copy or reprint is not required, but ap-propriate credit must be given to Crosslink and The Aerospace Corporation.

All trademarks, service marks, and trade names are the property of their respective owners.

Crosslink (ISSN 1527-5264) is published by The Aerospace Corporation, a California nonprofit corporation operating a federally funded research and development center that pro-vides objective expertise, analysis, and assessments in mul-tiple markets, including for government, civil, and commercial customers.

For more information about Aerospace, visit www.aero-space.org or write to Corporate Communications, P.O. Box 92957, M1-447, Los Angeles, CA 90009-2957.

Questions or comments about Crosslink may be sent via e-mail to [email protected] or write to The Aerospace Press, P.O. Box 92957, Los Angeles, CA 90009-2957.

On the cover: Susan Crain, research engineer, Space Instrumentation Department, holds a dosimeter built in the Aerospace laboratories in 1997 that weighed 3.63 kilograms (8 pounds) and used 4.5 watts of power. The miniature dosimeter she holds was devel-oped at Aerospace and licensed to Teledyne in 2009. It weighs 20 grams (.044 pounds) and uses less than 0.28 watts of power.

Crosslink®

The Aerospace Corporation magazine of advances in aerospace technology

Fall 2014

Pushing the Boundaries of Space

Visit the Crosslink Web site at www.aerospace.org/publications/crosslink-

magazine

CROSSLINK FALL 2014 1

This issue of Crosslink showcases some of the next-generation technical developments the company is pursuing and how these are being applied to The Aerospace Corporation’s customers and their space system programs.

The magazine presents a sample of the breakthrough technologies that are changing the landscape of possibilities for solving some of the toughest challenges in space today. In an era of cost constraints and reduced budgets, it is essential that Aerospace offer a leader-ship role to its customers in understanding these technologies, so that the national security space community can choose from the best solutions available to complex and varied issues.

Small satellites, miniature space sensors, next-generation commu-nication architectures—these and more are explored. Much of this work is happening in the laboratories, where Aerospace scientists and engineers push the boundaries of what is known, plot out the testing of new findings and theories, and explore whether what is discovered on Earth can be applied to space. Collaborating with other scientists and engineers throughout the world via sympo-siums, conferences, workshops, and the presentation of published papers helps ensure Aerospace remains a key player in the space community.

Aerospace innovation goes beyond the laboratory to include sys-tems engineering and integration. For example, the corporation is now providing the National Nuclear Security Administration with independent assessments and novel approaches in these areas, as well as with its risk management practices and procedures.

Aerospace has a long history of having its feet firmly planted in research and development. There is a renewed focus on this today, as the corporation actively seeks to emphasize the value that comes from investing in innovation and cultivating such a culture within its workforce. We hope this issue offers you insight into some of the company’s current efforts and work focus in this arena.

From the Editors

Courtesy of United Launch Alliance

Crosslink is published by The Aerospace Press. Its founding organization, The Aerospace Institute, is celebrating its 20-year anniversary in 2014.

CROSSLINK FALL 20142

PROFILE Margaret Chen, Associate Director, Space Sciences Department

Mission Assurance for the Space EnvironmentMargaret Chen has honed expertise in near-

Earth space and the magnetospheric environment

during a career spanning 22 years at Aerospace.

By Nancy Profera and Richard Park

Margaret Chen began her career at The Aerospace Corporation as a National Research Council post-doctoral associate developing a new physics-based

simulation model of Earth’s ring current for studying mag-netic storms. She has since performed research on charged-particle transport, acceleration, and loss, and wave particle interactions in Earth’s magnetosphere and ionosphere. Chen has also developed expertise in creating computer simula-tion models to better understand these space environment phenomena and their potential effects on satellites.

Born and raised in Southern California, Chen grew up in a supportive and scientifically oriented environment. Her parents each earned science degrees, her mother in physics and computer science, and her father in electrical engineer-ing. Her father began his career as an electrical engineer working at Ford Philco, and then later formed his own busi-ness that included food services and real estate. After being a stay-at-home mom for sixteen years, Chen’s mother went into the workforce. She started by managing a few of her husband’s business projects and then ventured into a career as a computer software developer and technical manager for Toshiba of America. “My parents taught me to be an independent thinker. They also taught me the importance of developing a career with work that I was passionate about,” said Chen.

Chen chose science as her own career, earning a bach-elor’s degree in physics and graduating magna cum laude from the University of California, Irvine, in 1984. She then enrolled in a physics Ph.D. program at the University of Cal-ifornia, Los Angeles. There, she met advisor and Professor of physics and astronomy, Maha Ashour-Abdalla, who was working on space science simulation efforts. “The work was very interesting to me, and that’s how I got started in space science research,” said Chen. “My graduate studies were in plasma physics, and the environment of space is 99 percent plasma, so it was definitely a good fit for me.” Her advisor collaborated with James Roeder, director of the Space Sci-ences Department, and that is how she learned about job opportunities at Aerospace.

During the course of her career, Chen has been awarded more than 15 National Science Foundation and NASA research grants. She has written 50 journal articles, given 31 invited conference presentations, and contributed to 166 other presentations. The research topics include under-standing the ring current, diffuse aurora, and plasma sheet dynamics during magnetic storms. She has recently added magnetosphere-ionosphere-thermosphere coupling to her research interests. Chen has also served as an editor for Geophysics Research Letters. In 2013, she was a recipient of Aerospace’s Woman of the Year award, recognized for her


contributions as the principal investigator of several inde-pendent research and development proposals, and for her efforts in the broader scientific community.

Space Science ResearchAs associate director of the Space Sciences Department at Aerospace, Chen explained, “We perform research on the near-Earth space environment and apply that knowledge to our customers’ needs. This helps us to prepare satellites and launch vehicles for the environmental effects they will face on their space systems.” The department’s current work is also focused on understand-ing ionospheric effects and propagation, anomaly resolu-tion, and threat analysis. Most recently, Chen has been able to apply her space environ-ment knowledge to the NASA Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission. The purpose is to gain a global view of the dynamic inner magnetosphere, the area of space in which charged particles are controlled by Earth’s magnetic field. Chen is the Aerospace program manager for this effort, and also a member of the TWINS science team. The work is done in collaboration with the Southwest Research Institute, which built the onboard instruments for data operations. Meanwhile, Aerospace personnel built many of the sensors on board. “It is exciting in that the space environment data we are gathering from the plasma and radiation sensors we built can now be used to serve all of our customers.” The space environment data is available for applications such as anomaly analysis as well as for scientific studies such as characterizing Earth’s magnetic cusp.

Another major space program effort Chen has been involved in is work on the U.S. Air Force’s Military Strategic and Tactical Relay System (Milstar). This constellation of five nuclear-survivable, secure, space-based communica-tions satellites has been collecting data for nearly twenty years, now comprising a large and valuable database. Chen has conducted statistical analysis of upsets for this program. This includes examining whether the space environment at geosynchronous Earth orbit (GEO) during those upsets is consistent with statistical distributions of past observations. “The historical references are used to make comparisons

to today’s space environment events, and this helps us to determine whether recent Milstar satellite upsets are out of character, or within the expected limits of the dynamic space environment,” said Chen. Her work in this area also helps Aerospace and the U.S. government address space environ-ment issues for future GEO spacecraft.

Chen’s role at Aerospace also involves strategic business planning, as well as mentoring and guiding younger staff members. The department regularly submits proposals to NASA and the National Science Foundation for grants and new work. Funding for research in the space sciences has

been decreasing, while secur-ing those funds is tougher and increasingly competitive. To address this challenge, Chen believes Aerospace must continue to engage and participate in the scientific community.

“One of the areas Aerospace has been successful in is our pub-

lishing papers, being on national and international leader-ship committees, organizing and attending conferences, and writing proposals for research grants. Being involved in the scientific community and gaining exposure through leader-ship positions is essential. It conveys that we are active play-ers in the research community,” said Chen.

When thinking about the future, Chen sees an emerg-ing trend of further collaboration among the space sci-ences community. For example, it has become increasingly clear that one model is no longer sufficient for space-based simulations; instead, global or coupled models are essential for a complete picture of the environment. “People used to concentrate their efforts on understanding a specific region in space, but it is now clear that we cannot understand the whole system unless we model the whole system. Everything is coupled in various ways, and we’re working toward a much more collaborative effort among the science community,” said Chen.

In closing, Chen said, “The space environment is ex-tremely variable. We must continue to develop our under-standing of the basic science of what is happening because there is still so much that is unknown. We are in a much better position to serve our customers’ spacecraft develop-ment efforts when we understand and can share with them what they will face in space.”

Being involved in the scientific community and

gaining exposure through leadership positions is

essential. It conveys that we are active players in

the research community.


Every new national security space system has its origin in some simple insight or concept. For example, the Global Positioning System (GPS) is based on the

principle that radio waves travel at the speed of light. Hence, the time it takes for a radio signal to travel from a satellite to a user can be multiplied by the speed of light to determine the distance between the two. This, together with principles from geometry, enables a user’s location to be determined by receiving radio signals from a sufficient number of GPS satellites.

Another example is that most satellite-based communica-tions exploit the insight that a satellite placed in precisely the correct orbit above the equator is geostationary. This greatly simplifies the use of ground antennas, since they can be installed to point at a single, apparently fixed, location.

These types of insights could not have been realized into actual space systems without an investment in the technolo-gy and innovation to back them up. For example, GPS would not exist without advances made in spaceborne atomic clock technology, and without the implementation of an innova-tive code division multiple access scheme that allows all sat-ellites to broadcast on the same frequency. These fundamen-tal breakthroughs are in turn based on hundreds of others, including innovative new technologies to detect and mitigate design and production errors in satellites as they are built.

National security space is now entering a new phase, where affordable space solutions and the need for resilience in an increasingly contested and congested environment have become paramount. This raises the level of challenge that new system concepts must face, whether the “new system” is an actual fresh start, a revectoring of an existing system, or an initiative to extract new capabilities from the synergistic interplay of current systems. To face this chal-lenge, a culture of innovation must be established at every level of the acquisition process–from early mission concepts to design, implementation, and deployment.

Understanding the ScienceScience and technology play a key role in innovation. For example, scientists continue to develop their understanding of the environment in which space systems operate based on dramatic improvements in and greater deployment of scien-tific instruments. This helps in the understanding of poten-tial space mission constraints and assists in decision-making about mission design. Likewise, gaining insight into the capabilities of emerging materials, such as carbon nanotubes, and how their properties act in the space environment—which can be significantly different from how they act in the terrestrial environment—may lead to space systems of considerable weight and cost savings.

To ensure a deep understanding of the key science-based issues facing national security space, The Aerospace Corporation maintains an aggressive program of use-inspired research. This means that Aerospace researchers press the boundaries of what is known and actively participate in the scientific community—publishing in refereed journals, par-ticipating in national and international forums, and collaborating with national laboratories and universities.

Having expertise in the science underlying new and emerging technologies enables Aerospace to help find answers to questions that have yet to be asked. New develop-ments in remote sensing, for example, may enable climate-monitoring missions not previously conceived, or might find application in a new technique for nondestructive investiga-tion of suspect parts in a rocket engine. Similarly, developing insights into the consumption of metallic rubidium by the glass walls of the lamp within a spaceborne atomic frequency standard may enable a more effective implementation of several space payloads.

Focus on the Underlying IssueIn today’s cost-constrained environment it becomes essen-tial to revisit the underlying requirements of a given space

Technology and Innovation: The Key to New System Development By Sherrie L. Zacharius


system. This is particularly true when looking at follow-on systems. If the requirements and constraints go unchanged, the solution is unlikely to be different. However, in an environment of rapidly changing threats, one can ask, “Are these still the right requirements?” Many times, the choices on how to proceed were derived from the original system requirements, and to find a truly innovative solution, it is necessary to identify the real underlying issue. In a rapidly changing world, the current issue may not be the one that was envisioned when the original system was conceived.

Aerospace is embarking on a program of internal special studies to evaluate new and emerging technologies in all areas—from breakthroughs in fundamental physics to the application of novel business models. These studies help Aerospace’s leadership and customers as they address the issues associated with developing new solutions in a chal-lenging era.

Aerospace also seeks to foster innovation at every level—questioning assumptions, finding unmet needs, exploiting new technologies, and developing new approaches within existing ones. For example, by exploring what can be done with very small satellites, Aerospace researchers have ap-proached the miniaturization of space from a new perspec-tive. Instead of asking how to shrink a large satellite mission into a smaller mass and volume, they start with a very small “CubeSat” class satellite design, then explore how much larger the small satellite needs to become to accommodate the full mission. In these cases, along the way, Aerospace helps energize the small satellite industry base for its cus-tomers by licensing its technical approaches to small satellite subsystems.

Collaborate for SuccessA technology-focused culture of innovation is essential for the national security space enterprise to succeed. Aerospace seeks to provide a leadership role in this arena but cannot go it alone. Thus, Aerospace is working to collaborate with part-ners at all levels—from government customers to national laboratories to prime contractors and small businesses to universities. This enables the enterprise to address large ef-forts, such as the search for solutions for the next generation of protected communications, in greater depth and fidelity than any one partner might bring to the effort.

The environment for national security space is rapidly changing, presenting a challenge to the nation in general and to Aerospace in particular. One thing is certain: just as the next war is never like the last one, the challenges of the future will not be like those of the past. Innovation and technology will play a vital and important role in achieving long-term mission success, helping to ensure a responsive and resilient national security space effort.

The newly constructed Propulsion Research Facility (PRF) on The Aerospace Corporation’s El Segundo, California, campus will enhance the ability of Aerospace to safely carry out empirical investigations of energetic systems used by national security space customers in launch vehicles and satellite propulsion systems.

The PRF brings to fruition a collaborative effort begun more than a decade ago between Aerospace's Physical Sciences Laboratories and the Vehicle Systems Division. The PRF is under construction with expected completion in the fall of 2014.

The 1200-square-foot building is located in the south parking lot area and will contain three primary laboratories: a chemicals handling and preparations wet lab; a laser diagnostics room; and a heavily reinforced main lab for carrying out controlled detona-tions of pyrotechnic devices, and hot-fire testing of rocket motors and their components.

Propulsion systems still account for the majority of launch vehicle failures, despite their long history of use and extensive industrial experience using them. Propulsion systems feature complex struc-tures characterized by high-energy densities and large thermal gradients. Materials are often exposed to extreme environments with narrow margins for maintaining structural integrity. Conse-quently, small material defects and deviations in nominal operat-ing conditions can quickly lead to spectacular failures, making

anomaly investigation and resolution paramount. The availability of a testing facility at Aerospace for the characterization of materi-als and systems under these extreme conditions is critical for the timely resolution of launch anomalies and failures, and for the mission assurance required by the corporation’s customers.

The Aerospace Propulsion Research Facility


Think Big, Fly SmallThe increasing popularity and functionality of small satellites has helped them move beyond

technology demonstration and into the realm of commercial and governmental applications.

Charles L. Gustafson and Siegfried W. Janson


In November 2013, a single Minotaur rocket carried 29 satellites into orbit, setting a new record for the most satellites deployed in a single launch. Less than two days

later, a single Dnepr beat that record, lifting 32 satellites into orbit. Such launch rates—inconceivable just a few years ago—are rendered all the more remarkable considering that many of these satellites were not sponsored by well-funded government agencies but by universities and small private entities.

Evidently, the space industry is starting to realize the potential of small satellites. Indeed, the last decade has seen a substantial boom in their development, both domestically and internationally. Much of this growth can be attributed to the popularity of CubeSats, a well-known subclass of small satellites. However, CubeSats are only part of this rapidly expanding picture. Furthermore, it appears that small satel-lites are starting to move beyond the demonstration phase to provide the performance and reliability needed for commer-cial ventures and governmental applications.

The CubeSat Revolution CubeSats derive their name from the so-called “1U” build-ing block, which is a 10 × 10 × 10 centimeter cube, typically weighing around 1 kilogram. Larger CubeSats are built by stacking these units. Bob Twiggs (then at Stanford Universi-ty) developed the initial concept in early 1999 after working with The Aerospace Corporation on his Orbiting Picosat-ellite Automated Launcher (OPAL) microsatellite. Jordi Puig-Suari from Cal Poly San Luis Obispo helped refine the concept and create the specifications.

The first CubeSat launched in June 2003; by the end of 2013, 155 had been placed in orbit, with 78 launched in 2013 alone. The United States, Russia, China, India, Japan, and the European Union all launched CubeSats in 2013. Almost 20 percent of the CubeSats launched that year were sponsored by the DOD. Aerospace has built and flown eight CubeSats since 2004 and is working on seven more.

CubeSats were originally conceived for education and flight tests of new technologies, but mission applications such as tactical communications, space weather measure-ment, and Earth observation are rapidly coming on line. The ability to design, build, test, fly, and redesign a spacecraft within one year is an obvious benefit for university stu-dents; but such fast development cycles also serve to spur the evolution of technologies and components for a wide range of future missions. These technologies can be applied to larger spacecraft to bring down launch and development costs. While the current launch architecture may not read-ily support the easy and timely launch of microsatellites in general, it does support the easy integration and launch of CubeSats. Standardization of the spacecraft and its deploy-ment system has provided multiple CubeSat launch opportu-nities each year with minimal risk to primary missions. Most are launched using a standardized ejection tube known as

Design Study 1: Microwave Weather Satellite

Mission:

Collect microwave weather measurements (ocean wind vectors, precipitable weather, cloud water, sea ice)

Design Specifications:

Spacecraft size: 100 × 100 × 140 centimeters³

Design life: 3 years

Orbit: LEO sun-synchronous (6 a.m.)

Altitude: 450 kilometers circular

Inclination: 97.2 degrees

Period: 93.6 minutes

Payload mass/power: 70 kilograms/50 watts

Spacecraft mass/power: 269 kilograms/263 watts

Stabilization: 3-axis

Pointing accuracy: 0.1 degrees

Pointing knowledge: 0.05 degrees

Hardware redundancy: Single string

Radiation environment: Natural

Payload mass and power growth: 25 percent, given that the payload is still in development

Spacecraft bus mass and power growth: 25 percent

Spacecraft disposal: Reentry within 25 years

Key Assumptions:

Spacecraft designs are unique and not based on any commercial or existing spacecraft designs

Other Considerations:

Launch: Minotaur 1

Mass exceeds ESPA Rideshare

Volume exceeds ESPA Grande

Refresh requirements variable with number of microsats


the Poly Picosatellite Orbital Deployer (P-POD), which can hold up to three units. These P-PODS fly on many interna-tional launch vehicles. A 1U CubeSat costs anywhere from $80,000 to $140,000 to launch—a bargain for government agencies, research centers, private companies, universities, high schools, and even individuals. For larger components, subsystems, or systems, 6U launch tubes are now available, and standards are being developed for 12U and 27U deploy-

ers. These will be large enough to deploy individual micro-satellites, potentially increasing the number and frequency of microsatellite launches in the future.

Recently, Twiggs (now at Morehead State University in Kentucky) introduced a new class of CubeSats known as PocketQubs. Measuring 5 × 5 × 5 centimeters, they can be bundled in groups of eight for deployment from a conven-tional P-POD or ejected individually by a Morehead Roma Femtosatellite Orbital Deployer (MR FOD). Four Pocket- Qubs were ejected in November 2013. A “1P” PocketQub called Wren was crowd-funded and built by the four-member German startup company StaDoko. Wren contains a camera, magnetic field sensors, three orthogonal reaction wheels, and four pulsed plasma thrusters for attitude and orbit control. At less than 200 grams, it replaced the Aero-space 250 gram, 2.5 × 7.5 × 10 centimeter OPAL Picosatel-lites, ejected into orbit in January 2000, as the smallest active satellite ever flown. That record was soon broken when another CubeSat in the same launch released Peru’s Pocket-PUCP femtosatellite, which measures only 1.55 × 4.95 × 8.35 centimeters and weighs just 97 grams.

Commercial Applications for Small Satellites Can microsatellites and smaller spacecraft really perform meaningful tasks? Many in the commercial sector believe they can. Several companies are marketing optical and near-infrared imagery as well as full-frame video collected by small satellites. In November 2013, Skybox Imaging launched its first satellite and began offering submeter reso-lution for visible-wavelength imagery and 30 hertz optical video at slightly lower resolution. The satellites have a mass of approximately 100 kilograms, with a central core less than a meter long.

Planet Labs launched four 3U CubeSats during 2013 to serve as demonstrators for the much larger Flock-1 constel-lation to provide regular refreshes of imagery anywhere on Earth. The satellites can achieve a ground sample distance of approximately 5 meters (assuming a 500-kilometer circular orbit) with an evident aperture of less than 10 centimeters. In January 2014, Planet Labs sent 28 additional spacecraft to the International Space Station and deployed all of them by March to generate the world’s largest constellation of Earth imaging satellites. The company has announced plans to launch an additional 100 CubeSats by April 2015.

Another commercial application for small satellites is communications. In low Earth orbit (LEO), such satellites can provide a variety of services, including messaging, e-mail, and localization, and services to mobile users. Unlike large geostationary communications satellites with high-gain anten-nas and high data rates, small satellites in LEO (or “little LEO” constellations) specialize in low-to-medium data rates using low-gain, low-power terrestrial transceivers.

In the 1990s, ORBCOMM launched 35 small satellites to provide commercial machine-to-machine messaging in the

The CubeSat program has enabled Aerospace to design, build, and flight- test a number of satellite components. Shown here is the second-generation Earth nadir sensor, which achieves a pointing accuracy of 1 degree.

Image of an almost completely frozen Lake Superior taken by AeroCube-4, a 1U CubeSat.


137–150 megahertz VHF band, with a 4.8 kilobits per sec-ond downlink and a 2.4 kilobits per second uplink. The sat-ellites weighed about 42 kilograms each and were launched on Pegasus and Taurus vehicles into 775-kilometer circular orbits; 25 are operational today. In 2008, ORBCOMM launched a set of six replacement satellites, each weighing 80 kilograms. These all failed due to a power system anomaly, but a new generation of 18 satellites is in production, with launches planned on the Falcon 9 vehicle. These satellites will weigh 142 kilograms and will include support for the Automatic Identification System, which is used to track ocean vessels.

Government ApplicationsSpurred in part by successful commercial developments, the U.S. government has also started examining applications for small satellites. In 2013, the Air Force Scientific Advisory Board completed a study for Air Force Space Command (Aerospace is a member of the board). The study found that microsatellites “have significant near-term (2–5 years) mis-sion capability.” In particular, the study concluded that:

Microsats can address all Category A weather require-ments; microsats can address some critical space situational awareness (SSA) requirements; other potential near- and mid-term microsat missions exist in space-to-surface intelligence, surveillance, and reconnaissance (ISR) and position, naviga-tion, and timing (PNT); and potential far-term microsat missions exist in missile warning, PNT, and communications. In addition, the study found that:

Microsats are not currently well supported by Air Force

launch architecture; microsat ground system costs could pre-vent effective mission application; and more suitable ground command and control (C2) architectures and processes exist.

Thus, small satellites can satisfy specific sets of require-ments within certain missions—and the number of applica-tions could increase in the future. It is important to note, though, that small satellites are definitely not suitable for many Air Force missions and requirements—for example, protected and nuclear-survivable communications. Small satellites are inherently less capable than large satellites in satisfying requirements for high-power-aperture products. Small satellites are not now, nor will they ever be, a panacea for Air Force Space Command.

It is also important to note that in cases where small satellites do have application, they will require different launch and ground systems than those used for large satellites. Without approaches that better suit small satellites, it may not be possible to effectively use them for Air Force missions.

The findings of the Scientific Advisory Board were sup-ported by proof-of-concept engineering designs created at Aerospace. Two of these designs focused on microwave imaging and space-based surveillance.

The microwave imaging satellite was designed for weather monitoring using a specific payload currently in development. It featured three-axis stabilization and a pointing accuracy of 0.1 degree. Design life was three years. Measuring 100 × 100 × 140 centimeters and weighing 269 kilograms, it exceeded the size limits for the EELV Second-ary Payload Adapter (ESPA), and would require a dedicated launch on a small vehicle (such as a Minotaur 1).

The launch rate for small satellites has increased in the last 20 years, driven by significant increases in the number of picosats and nanosats launched. All 1U CubeSats are counted as picosats, and all larger CubeSats are nanosats. The

vast majority of nanosats are 1.5 through 3U CubeSats, and the vast majority of picosats are 1U CubeSats.

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The surveillance satellite was designed to detect and track geostationary objects—a function currently provided by the Space-Based Space Surveillance system (SBSS). The design clearly showed the feasibility of using a microsat to host an optical payload capable of sensing small objects in geosyn-chronous orbit from LEO. Compared with the current SBSS mission profile, this approach would achieve substantially lower complexity and lifecycle cost. Moreover, the revisit rate could be gradually increased through incremental ad-dition of capability, with a relatively manageable funding profile. The same capability could be used for high LEO and medium Earth orbits, if needed, providing a consistent ap-proach to object detection and tracking. Overall, the panel concluded that this is a high-payoff area for microsat use.

CubeSats in ActionTypical CubeSat missions in 2013 included flight-testing new technologies, hands-on education, store-and-forward com-munications, space science measurements, and Earth obser-vation. Aerospace is helping the U.S. government develop several new mission areas. Some examples of government-

sponsored Cubesats launched in 2013 include:• AeroCube-5A and -5B. These 1.5U CubeSats were de-

signed, built, and tested at Aerospace. They will demon-strate improved pointing capabilities needed for future missions and flight-test the CubeSat Terminator Tape Deorbit Module from Tethers Unlimited.

• SENSE-A and -B. These 3U CubeSats were sponsored by the Air Force Space and Missile Systems Center/De-velopment Planning Directorate (SMC/XR) and built by Boeing. They will demonstrate collection of space weather data and timely integration of that data into ground-based ionospheric models for improved predictions.

• SMDC-ONE-2.3 and -2.4. Eight of these 3U CubeSats were developed by Miltec for the U.S. Army Space and Missile Defense Command to receive and forward data from unattended ground sensors and to provide voice and text message relay for field units.

• ORSES. This 3U CubeSat was developed by the Opera-tionally Responsive Space office and the U.S. Army Space and Missile Defense Command to provide communica-tions and data capabilities for underserved tactical users.

• STARE-B. This 3U CubeSat was developed by Lawrence Livermore National Laboratory to test the Space-based Telescopes for Actionable Refinement of Ephemeris (STARE) concept. STARE, in conjunction with ground-based assets, could provide improved accuracies for the orbital elements of space debris. Better orbital ephemeri-des should produce fewer false alarms during collision prediction routines, resulting in fewer collision-avoidance maneuvers for all LEO spacecraft.Because there are multiple launch opportunities each

year, it is now possible to design, build, fly, and analyze flight data within a year. This is 5 to 7 times faster than the traditional development cycle, thus accelerating the evolu-tion of new technologies for small satellites—e.g., solar cells, microprocessors, field-programmable gate arrays, attitude sensors, GPS receivers, etc. For example, Aerospace has developed triaxial reaction wheels and Earth nadir sensors that fit within a 1-cubic-inch volume, and a GPS receiver that occupies about 2 square inches of circuit board space. These subsystems were on at least two previous spacecraft, and the development team is now on its third cycle of modi-fications, based on flight performance, to improve accuracy and reliability. The second-generation Earth nadir sensor has 1-degree pointing accuracy.

For the NASA-sponsored Optical Communications and Sensor Demonstration (OCSD) mission, which will fly in 2015, Aerospace is developing a star tracker with less than 2-cubic-inch volume to provide pointing knowledge better than 0.05 degree; an approximately 10-cubic-inch, 5-to-200–megabits per second laser transmitter; and a 6-cubic-inch warm-gas propulsion system. The laser transmitter will enable unprecedented communication rates for a CubeSat. A terabyte of memory—in the form of eight or more 128-giga-

Mission:

Observe GEO targets with a LEO microsat

Design Specifications:

Spacecraft size: 60 × 60 × 60 centimeters³

Design life: 3 years

Orbit: LEO

Altitude: 700 kilometers circular

Payload mass/power: 29 kilograms/26 watts

Spacecraft mass/power: 119 kilograms/106 watts

Key Assumptions:

Limiting technology is pointing accuracy

Two or more microsats in a circular LEO orbit

Other Considerations:

Technology readiness level: 3/5 system/components

GEO object detection and tracking from sub-GEO and super-GEO are plausible

Design Study 2: LEO to GEO Tracker Satellite

pointing angle

GeOST in low altitude, zero inclination, circular orbit


bit Flash memory cards—can literally be held in the palm of the hand. Unfortunately, it would take more than a hundred years to download a terabyte of data using a typical small satellite radio frequency downlink (at about 100 kilobits per second) from LEO using a single ground station. The laser downlink will demonstrate a new communications channel with a 2 to 3 order of magnitude increase in data rate for CubeSats and other small satellites.

The OCSD mission is one of four CubeSat flight pro-grams supported by NASA’s Small Spacecraft Technology Program. The other three are: the Edison Demonstration of Small Satellite Networks, a free-flying cluster of eight CubeSats that will take space radiation measurements and crosslink information between spacecraft; the Integrated Solar Array and Reflectarray, a Ka-band antenna integrated into a solar array for up to 100 megabits per second data rates to a ground station; and the CubeSat Proximity Opera-tions Demonstration, a rendezvous and docking mission using two 3U CubeSats.

NASA’s first CubeSat, GeneSat-1, reached orbit in December 2006 to conduct space biology experiments. Subsequent space biology CubeSats flown by NASA include PharmaSat (2009) and the Organism/Organic Exposure to Orbital Stresses spacecraft (2010). Also in 2010, NASA built and flew a solar-sail experiment, NanoSail-D2, which packed a 10-square-meter sail into a 3U CubeSat (which is only 30 centimeters long).

In 2012, NASA announced the In-Space Validation of Earth Science Technologies (InVEST) program, targeted spe-cifically at CubeSats. Four out of 23 submitted projects were selected. The winners were MIT Lincoln Laboratory, the Johns Hopkins University Applied Physics Laboratory, the Uni-versity of Maryland, and The Aerospace Corporation, which proposed “A CubeSat Flight Demonstration of a Photon-Counting Infrared Detector.” The 3U CubeSat, containing a cryocooled, state-of-the-art photon-counting detector array, will fly in 2016.

NASA is also funding a wide range of technologies for small satellites and CubeSats at universities, private com-

panies, FFRDCs, and various NASA centers. Aerospace has embarked on a NASA-funded effort to develop an advanced hybrid-rocket motor propulsion unit for CubeSats in col-laboration with Pennsylvania State University. Other NASA-sponsored CubeSat propulsion efforts include development of a hydrazine propulsion module, a radio-frequency ion engine that uses iodine as propellant, a “green” (nontoxic) propulsion module, and an electromagnetic plasma thruster.

SummaryThe U.S. space program started with the launch of Explor-er-1, a 14-kilogram microsatellite, followed by Vanguard-1, a 1.7-kilogram nanosatellite. More than five decades of tech-nological advancements have packed greater functionality into microsatellites and smaller spacecraft. This has driven down cost per unit and expanded the deployment of new spacecraft by many countries, corporations, organizations, and even individuals. CubeSats are one example of a “new” spacecraft that has radically changed the small satellite field. Basic laws of physics place limits on phenomena such as ground resolution and antenna gain for a given aperture di-ameter, so small satellites cannot be used for many demand-ing military applications. On the other hand, small satellites are relatively inexpensive and can be distributed in constel-lations to provide simultaneous measurements, or reduced revisit times, with reduced spatial resolution. The microwave imager sounder and GEO satellite tracker that Aerospace studied demonstrate the feasibility of this approach. Com-mercially, microsatellites have already been used to provide LEO data communications, and further improvements in data rate and availability are possible. Thanks to its early involvement in this field, Aerospace is well positioned to help the U.S. government take advantage of the intriguing possibilities.

Further Reading

The Aerospace Corporation, “Photos from Space,” http://www.aerospace.org/2014/01/30/photos-from-space//

W. Graham, “Russian Dnepr Conducts Record Breaking 32 Satellite Haul,” NASASpaceFlight.com (Nov. 21, 2013).

Q. Hardy and N. Bilton, “Start-Ups Aim to Conquer Space Market,” New York Times (March 17, 2014).

H. Helvajian and S. Janson, Small Satellites: Past, Present, and Future (The Aerospace Press/AIAA, El Segundo, CA, 2008).

S. W. Janson and R. P. Welle, “The NASA Optical Commu-nication and Sensor Demonstration Program,” SSC13-II-1, 27th Annual AIAA/USU Conference on Small Satellites (Logan, UT, August 12-15, 2013).

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The number of nations and government consortia active in space has steadily increased over the last 50 years.


Internal Research and Development Spurs Advancements and Fills Technology Gaps

Aerospace internal research has led to real-world components

that vastly miniaturize space environment sensors.

T. Paul O’Brien


The environments of near-Earth space and the upper atmosphere pose unique chal-lenges for designing and operating satellite

systems. For example, radiation can disrupt criti-cal electronic systems in satellites. Understand-ing such phenomena is important for designing and operating space systems. The Aerospace Corporation has cultivated the capability to design, develop, and produce such instruments and technologies, which have helped numerous space missions succeed.

However, the instruments and technologies needed to measure the space environment have often been weighed down by unnecessarily large custom electronics. Recognizing this challenge, Aerospace has made a significant investment during the past several years in miniaturizing the electronics required by space environment sensors.

Promising work has been done in the field of application-specific integrated circuits (ASICs) for space environment sensors. An ASIC is a set of miniaturized electronic circuits that is customized for a particular use rather than a more typical assembly of discrete general-use components.

Because of their reduced mass, power, and size compared to discrete components, ASICs can offer greater capability in instruments on satellite systems. ASICs have dramatically altered the design of space environment sensors and enabled vast improvements in their capabilities despite fixed resourc-es and other limitations.

Scientists and engineers in Aerospace’s Space Science Applications Laboratory began work on ASIC applications in space environment sensors as an independent research and development program in 2002 (“Mixed-Signal ASIC Design for Microsat and Smallsat Applications”). This effort capitalized on decades of experience in designing, building, and launching spaceflight instruments to measure the space radiation and plasma environments.

The goal was to reimplement those common functions in a physically compact, low-resource, easily manufactured chip. The first application chosen for development was the microdosimeter, based on its relevance to and suitability for all satellites, especially small ones. A dosimeter measures radiation dose, which is the deposit of energy through ion-ization and mechanical or chemical reactions.

Simultaneous Development EffortsAt the same time the ASIC development effort started, Aerospace began a larger internal research effort, the Space Weather Initiative, which included a project to develop space situational awareness tools for anticipating and diagnosing

anomalies caused by space weather. As a part of this project, the initiative funded the development of a visualization ca-pability for Aerospace’s Spacecraft Environmental Anomalies Expert System, Real-Time (SEAES-RT).

SEAES-RT was developed for the Rapid Attack Identi-fication and Detection Reporting System (RAIDRS). This ground-based system detects and classifies instances of radio-frequency interference to satellites and their ground elements. The original SEAES was an interactive system that was used after space weather anomalies occurred. SEAES-RT auto-matically assembled data from sensors on the ground and in geostationary orbit to provide space situational awareness in the widely used red-yellow-green stoplight format.

To address concerns that the data sources for SEAES were insufficient, the Space Weather Initiative investigated the possibility of dedicated satellite constellations for moni-toring space weather. One of the initiative’s key insights was that some hazards were so localized, even a dense constel-lation of monitoring satellites could not adequately define them. Instead, an environmental sensor was needed on every satellite. The microdosimeter was the first step toward that goal: a sensor so small and simple that it was a component, not a payload.

Microdosimeter DevelopmentAerospace scientists successfully developed a microdosim-eter about the size of a postage stamp with the insight and guidance learned from the Space Weather Initiative, along

Microdosimeter data, incorporated into the Spacecraft Environmental Anomalies Expert System (SEAES), supports space situational analysis and anomaly resolution for satellites in low Earth orbit. Here, near-real-time data from the microdosimeter payload is fed into a SEAES demonstration on a classified system. The data is mapped from the Rapid Pathfinder to other low Earth orbit vehicles. SEAES then produces hazard maps. This map shows the radiation dose behind thinly shielded com-ponents both along the Rapid Pathfinder ground track and in contours. The red regions indicate loca-tions of elevated risk of anomalies caused by single-event effects, internal charging, and total dose.


Crowd-sourcing weather data has a long history and is still in use at sea, in the air, and on land. The arrival of microdosimeter tech-nology may lead to crowd-sourced weather in space as well.

Mariners record sea surface and weather conditions and share this information with organizations like the National Oceanic and Atmospheric Association (NOAA) for use in operational and climatological weather and marine products. These products allow other ships to navigate and operate more successfully.

The World Meteorological Organization’s Voluntary Observing Ships (VOS) program employs lightly trained volunteers operating government-supplied equipment aboard thousands of vessels. Prior to the age of satellite weather observations, the VOS scheme was the only way to cover the vast oceans. Today’s offshore weather is tomorrow’s onshore weather. In the satellite age, the VOS system remains a vital part of monitoring the ocean surface and offshore weather.

Following the model of mariners, aircraft pass along weather ob-servations, especially clear air turbulence, to air safety controllers. Because turbulence is difficult to detect remotely, the air safety system relies on routine reports from pilots flying through rough air. Relayed through the air traffic control system, turbulence reports lead to warnings from the cockpit for passengers to take their seats and fasten their seat belts. In those rare cases when severe turbulence is encountered without warning, it is common for passengers and flight crew to receive serious injuries. Thus, crowd sourcing of atmospheric conditions probably prevents seri-ous injuries every day.

The advent of the Internet has dramatically reduced barriers to forming a crowd-sourced weather observation network. For example, today the Community Collaborative Rain, Hail, and Snow Network (CoCoRaHS) provides a coordinating umbrella for thousands of volunteer precipitation observers around the United States. These volunteers make daily standardized measurements using equipment often purchased themselves. The shared data of-fers a wide variety of users a supplement to the more capable–but also more expensive–national weather station network.

The methods and value of crowd-sourcing has an obvious analogue in space weather. Social media applications have been developed to catalogue and map observations of the aurora. However, as yet, satellite operations have not been able to take advantage of crowd-sourcing. All of the examples here required a low-cost means of observing the relevant weather conditions–special equipment or the five senses of humans on the scene. This is why the microdosimeter is a potential game changer: it weighs only 20 grams; interfaces to common, existing electrical and housekeeping data infrastructure found on most satellites; and can measure radiation dosage as small as 14 microrads. Radiation-sensing field effect transistors (RadFETs), which employ an older technology in the same size scale as the microdosim-eter, are orders of magnitude less sensitive–microdosimeters can

resolve radiation environment structures that a satellite traverses in seconds, while RadFETs can typically only observe changes from one orbit to the next, or even one day to the next.

Equipped with microdosimeters or similarly accurate, targeted sensors, satellites could routinely report their conditions back to a central authority through ground-based communication networks, in direct analogy to VOS or CoCoRaHS. Satellites move quickly through different radiation regions, so their reports would need to have fairly high-time resolution (seconds to minutes, depending on the orbital period). For maximum utility, the reports would need to have low latency (minutes); although, for anomaly resolution, data with latencies up to a day or two can still be very useful.

VOS and CoCoRaHS, in contrast, typically have lower time resolu-tion and higher latency; therefore communications infrastructure will play an important role in realizing a crowd-sourced, space-based radiation observation network. Once the data from distrib-uted sensors are assembled, however, data-assimilative models could ingest dosage and location data to fill in the global environ-ment on a high-resolution grid and estimate upcoming conditions along the specific track of any vehicle.

More latent data could be used to accurately reconstruct the global environment for anomaly resolution. In either timeframe, the crowd-sourced network would support vehicles with and without their own environmental sensors. An ad hoc distributed approach would be especially helpful in low-altitude, medium- altitude, and highly elliptical orbits, all of which cross through different regions of the radiation belt, and are, therefore, sensitive to more details of the radiation belt structure and dynamics than a geostationary platform. The first critical technology along this path is the microdosimeter developed at The Aerospace Corporation.

Looking farther ahead, the biggest hole that would be left by a crowd-sourced network of dosimeters is the spacecraft surface charging hazard posed by hot electron plasmas. These plasmas are too low in energy to penetrate the surface of the spacecraft (or the dosimeter), but the charging they cause can lead to electrostatic discharge, which can destroy strings of solar cells, issue phantom commands, create short circuits, or simply burn spacecraft components and materials.

The same Aerospace team that developed the microdosimeter is developing a charge deposit sensor to characterize the surface charging hazard. The plasma that causes this charging is known to be sufficiently variable in time and space. The consensus is to fly one or more surface charging monitors on every vehicle. Whether that solution is ever realized, the crowd-sourcing infrastructure is the same as what would be needed for radiation dosimetry. In fact, it may turn out that with a sufficiently dense crowd-sourced network of ad hoc surface charging sensors, some orbit regimes, such as geostationary orbit, may not need a surface charging sen-sor on every vehicle, just on a lot of them. Aerospace looks to the future as it continues to develop these enabling technologies.

Crowd-Sourcing Space Radiation Hazard Monitoring


with a sequence of continuing independent research and development projects. The microdosimeter weighed only 20 grams and consumed as little as 144 milliwatts. More impor-tant, it was powered by a range of common bus voltages and could have up to four outputs, each of which was the same electrically as a common thermistor output.

In 2006, Aerospace filed a patent application for its micro-dosimeter. Once a patent was issued, Aerospace licensed the technology to Teledyne Microelectronic Technologies for manufacture and sale.

The microdosimeters can be launched on almost any sat-ellite needing space situational awareness. They are currently implemented in spacecraft at low Earth orbit, geostation-ary transfer orbit, and even lunar orbit. These components provide valuable data for space situational awareness, space weather anomaly resolution, and verification of satellite de-sign models. In fact, the microdosimeter’s compactness and high precision have opened up other opportunities in ground and atmospheric radiation dosimetry, such as monitoring crew radiation dose on transpolar or high-altitude flights.

While comprehensive, highly capable space environment sensors will always be needed, the microdosimeter has estab-lished a new niche: compact, targeted sensors that measure the effects of the space environment, rather than the particles that cause those effects. Aerospace followed up on the micro-dosimeter with a charge-deposit sensor, which measures sur-face charging on a spacecraft, and an electrostatic discharge recorder, which counts and digitizes high-frequency electri-cal transients indicative of electrostatic discharge, the likely cause of many satellite anomalies.

Other ASIC ApplicationsAfter the success of the targeted sensors, Aerospace research-ers turned their attention to developing ASICs for more sophisticated sensors that performed such common tasks as fast coincidence logic and pulse-height analysis. Fast coincidence logic measures the nearly simultaneous energy deposits in multiple detector elements as a single particle passes through them. Pulse-height analysis examines the size of the electronic pulses generated by these energy deposits.

Such sensors were needed on several NASA programs, in-cluding the Van Allen Probes, the Magnetospheric Multiscale mission, and the VISIONS (Visualizing Ion Outflow via Neu-tral Atom Imaging During a Substorm) sounding rocket. For these programs, Aerospace designed new ASICs to perform these common tasks and gave them colorful names such as MAPPER, DAPPER, and MRA. These new ASICs enable more capabilities within the same limited volume that used to be occupied by analog and digital signal processing circuit boards. For example, a single MAPPER chip can replace up to 12 boards of discrete analog electronics.

Because of the modularization and the reduced volume, mass, and power in ASICs, Aerospace researchers have been able to solve tough challenges in developing space environ-ment sensors. For example, the fast coincidence logic and pulse-height analysis ASICs are implemented in the magnetic electron ion spectrometer (MagEIS) that Aerospace devel-oped for NASA’s Van Allen Probes.

MagEIS uses coincidence to reduce out-of-view back-ground by rejecting particles that do not strike all the required elements in the sensor. The physical alignment of these elements limits the trajectory of particles that can be counted as foreground and rejects all other particles as background.

The MagEIS pulse height analysis capability allows the sensor to estimate and remove background from particles that scatter within or penetrate through the sensor material. By examining the combination of energy deposits in the vari-ous sensor elements, background particles can be identified for exclusion.

As a result of miniaturization, each of the Van Allen Probes carries four MagEIS units with different energy or angular coverage. A previous mission, the Combined Release and Radiation Effects Satellite, carried only one.

10.9 inches

The microdosimeter became commercially available in 2010. Aerospace has licensed the technology to Teledyne Microelectronics for production.

Courtesy of Teledyne Microelectronics

The microdosimeter payload on the Rapid Pathfinder in low Earth orbit. The hardware was designed by Aerospace to support technology demonstration and vehicle anomaly resolution.

Courtesy of Millennium

Space Systems


The Radiation Belt Storm Probes (RBSP) mission is part of NASA’s “Living With a Star Program,” designed to explore the fundamental processes that generate hazardous space weather effects near Earth. NASA selected the Applied Physics Laboratory at Johns Hopkins University as the satellite prime contractor and a team of researchers, scientists, and engineers from The Aerospace Corporation to provide the instrument payload for the mission.

Named the Van Allen Probes mission in honor of the work of James Van Allen in discovering and charac-terizing the space radiation environment, the two spacecraft designed for this mission were launched from Cape Canaveral, Florida, on August 30, 2012, into highly elliptical orbits that cross the inner and outer Van Allen belts. The probes are gathering data with the necessary spatial and temporal resolution to answer long-standing questions about the dynamics of the natural radiation environment.

Building on decades of experience in the design and construction of spaceborne instruments, Aerospace scientists and engineers conceived, designed, and built two unique instrument packages for the Van Allen probes mission—the Magnetic Electron Ion Spectrometer (MagEIS) and the Relativistic Proton Spectrometer (RPS) to measure with unprecedent-ed accuracy the outer and inner Van Allen radiation belts. Outfitted with the instruments, the Van Allen Probes have now unambiguously detected the presence of transient regions of increased radiation surrounding Earth, revealing the existence of important structures and processes within these hazardous regions of space. Data of this type are essential for the next version of the AE9/AP9 environment specification models.

Data from the MagEIS instruments have provided the first clear evidence of a fundamental plasma physics process known as drift resonance, operating in Earth’s magnetosphere. This is illustrated in the figure to the right, where azimuthally drifting outer zone electrons (energy ap-proximately 100 kiloelectron volts) resonantly exchange energy with electromagnetic waves. The interaction occurs when the period of the electromagnetic oscillation (panels b and c) matches an integer multiple of the electron drift period. The particle flux oscillations are in phase with the wave at the resonant energy (approximately 80 kiloelectron volts) and show the characteristic phase lag at energies above and below this value (panel a).

In addition to advancing scientific knowledge, Aerospace scientists and

Aerospace Develops Instruments for Van Allen Probes

Outer radiation belt (electrons) Inner radiation belt (protons)

Van Allen probes B

Van Allen probes A

Custom application-specific integrated circuits incorporated in a magnetic electron ion spectrometer. The spectrometer depends heavily on these circuits for signal processing and background removal. The resource savings from this setup allows a spacecraft to carry four spectrometers, whereas a previous mission from 1990 to 1991 could only carry one.

ConclusionAs of 2011, microdosimeter data from the Rapid Pathfinder satellite are being sent in near real time to a SEAES dem-onstration supporting that vehicle and others in low Earth orbit. This convergence of microdosimeter and SEAES development partially realizes the vision of ASIC-based sen-sors providing space situational awareness for all satellites.

While the goal of having a space environment sensor on every satellite has not been realized, the technical hurdles have mostly been overcome. ASICs can be found as criti-cal enabling technologies in many targeted and scientific space environment sensors developed at Aerospace. ASIC technology is also being implemented in national security, civil, and commercial space applications. Developing ASIC technology to reduce the resource requirements for onboard space environment sensors has been a long-term develop-


ment effort that was born from and often sustained by the Aerospace Technical Investment Program.

Further Reading

Aerospace Report No. ATR-2003(8194)-2, “GPS Observa-tions of the Upper and Deep Atmosphere: (GOUDA)–Phase A Study” (The Aerospace Corporation, El Segundo, CA, 2003).

Aerospace Report No. ATR-2003(8194)-1, “Space Weather Instrumented Sentinel System (SWISS-GEO)–Phase A Study” (The Aerospace Corporation, El Segundo, CA, 2003).

Aerospace Report No. ATR-2008(8073)-2, “On-Board Space Environment Sensors: Explanations and Recommendations” (The Aerospace Corporation, El Segundo, CA, 2008).

Aerospace Report No. ATR-2009(8073)-2, “Spacecraft

Environmental Anomalies Expert System (SEAES)–IR&D Developments FY06 to FY09” (The Aerospace Corporation, El Segundo, CA, 2009).

J. Blake et al., “The Magnetic Electron Ion Spectrometer (MagEIS) Instruments aboard the Radiation Belt Storm Probes (RBSP) Spacecraft,” Space Science Review, Vol. 179, pp. 383–421 (June 2013).

J. Mazur, W. Crain, M. Looper, D. Mabry, et al., “New Measurements of Total Ionizing Dose in the Lunar Environ-ment,” Space Weather, Vol. 9, No. S07002 (July 2011).

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engineers are also using data from the Van Allen probes to develop new space radia-tion environment models for satellite design and mission trade studies. While the AE8 and AP8 models, which have been the industry benchmarks for several decades, output an estimate of the average energetic-particle flux, they do not provide information on the natural variability of the environment. Quantifying the percentiles of the environment will enable the trade of space hazards mitigation against other system trades.

The recently released AE9 and AP9 models output a detailed statistical estimate, but addi-tional radiation measurements are needed for the models to achieve their full capability, and give spacecraft designers the accuracy they need to develop long-lived space assets with-out unnecessary and costly overdesign. The results Aerospace gathers from these probes will allow more rigorous analysis of the risk to planned missions from radiation hazards, such as total dose degradation of microelectronics, internal electrostatic discharge, and back-ground noise in imaging sensors. Preliminary RPS data have already influenced the system trades and designs for future national security space missions.

– Seth Claudepierre, Ionospheric and Atmo-spheric Sciences, Space Sciences Department

In this figure, azimuthally drifting outer zone electrons (energy approximately 100 kiloelectron volts) resonantly exchange energy with electromagnetic waves.


2025 and Beyond: The Next Generation of Protected Tactical CommunicationsDeveloping affordable, protected, and interoperable satellite

communications systems are goals of tomorrow’s space

and ground architectures.

Jo-Chieh Chuang, Joseph Han, and Bomey Yang


In 2011, the U.S. Air Force’s Joint Space Communication Layer (JSCL) Initial Capabilities Document (ICD) projected military communication needs for 2025 and beyond. It

envisions Military Satellite Communications (MILSAT-COM) capacity in a contested environment will increase significantly in coming years, and surpass current program capabilities. Several new MILSATCOM capabilities were identified, including increasing connectivity, antijamming protection in a contested environment, data rates higher than 512 kilobits per second for protected communications on the move (PCOTM) terminals, increasing of capacity in concentrated theaters, and significant high data rate and ca-pability to support remotely piloted airborne (RPA) missions with secure command and control and mission data. The U.S. government wants to provide significant enhancements to MILSATCOM capabilities for tactical missions, but at the same time, needs to reduce overall costs because of budget reductions.

To meet these challenges, the Air Force SMC/MCX (Ad-vanced Concepts Division) initiated a 90-day MILSATCOM architecture study in 2011. Aerospace was the technical lead and a major contributor to the study, including introducing a disaggregated concept that separates strategic and tactical mis-sions. Aerospace presented more than 80 technical reports to the MILSATCOM community during 2011–2012. The study result was well received by the Air Force’s Space and Missile Systems Center (SMC) leadership and the U.S. Congress.

Based on the results of this study, the Air Force es-tablished the “Military Satellite Communications Space Modernization Initiative Investment Plan,” which led to the two-year, protected military satellite communications effort “Design for Affordability Risk Reduction” begun in October 2012. The study and hardware/software demonstrations in-clude the U.S. government-owned (nonproprietary) protected tactical waveform (PTW), as well as protected tactical service (PTS) system concept developments. The study also includes an assessment of the overall space communication architec-ture, commercial-like mission management subsystem func-tions, gateway design for network interoperability, informa-tion assurance practices, and affordable terminal design.

Aerospace has actively participated in this effort, assisting

the U.S. government in establishing requirements, includ-ing multiple scenarios for contractors to conduct analysis and trade-offs; performing analysis of the protected tactical waveform; designing government reference architectures for cost estimates and performance analysis; conducting relevant systems engineering studies for multiple communication architectures; and evaluating contractors’ analysis and results.

The Protected Tactical Waveform The PTW aims to support future protected tactical systems. The U.S. government initiated its development with Aero-space, other federally funded research and development centers (FFRDCs), and military terminal program offices (TPOs) in late 2011. Seventeen contractors contributed to the development of the PTW under the protected Broad Agency Announcement (BAA) Phase I contract from Octo-ber 2012 to July 2013. Since then, the government, FFRDCs, and TPOs continue to refine the PTW.

The PTW is designed with frequency-hopping spread spectrum (FHSS) to provide greater antijamming capabil-ity, featuring a mix of the current protected waveform and the commercial waveform. The PTW has several significant design features, including: • It will support unclassified terminal development for

forward users in a high-risk environment. For example, it will support the U.S. Army PCOTM to the Company level for high-data-rate antijam capacity (at 512 kilobits per second). This capability addresses new features noted in the JSCL and will reduce the terminals’ cost, since classi-fied terminal cost is a significant part of the total protected MILSATCOM cost.

• It will support multiple user groups through table-based TRANSEC. In this design, if a terminal is compromised, the impact to the mission is limited to the particular user group. The other terminals in the affected user group can be quickly rekeyed because only a subset of the total terminals would require rekey.

• It supports multiple satellite communication architec-tures, from simple transponder satellites (commercial or Wideband Global SATCOM [WGS]) to complicated, fully processed satellites of the future. These features enable

The protected tactical waveform supports all four of the existing satellite com-munication architectures: pure transponder, dehop/rehop transponder, partial processed, and full processed.


enterprise and resilient capability by multiple SATCOM systems because different antijam capabilities can be achieved by multiple SATCOM architectures.

• It is capable of frequency-hopping and will have com-parable antijam capability for current protected systems from the waveform point of view. Other antijam per-formance differences will depend on the space payload design, frequency-hopping bandwidth, and attenuation loss of different frequency (Ku, Ka, or EHF).

• It has new functions to support forward (downlink to users) antijam capability by short interleaver. This new feature will ensure the robustness of the antijam capabil-ity for command and control (C2), while providing high data rate at up to 137 megabits per second for RPA user data. This feature addresses JSCL for future RPA applica-tions.

• It supports noncontiguous bandwidth-hopping capa-bility, which can occur between fixed frequency bands without interfering with existing users on WGS or com-mercial satellites. This feature allows for greater flexibil-ity of satellite operations.

• It adopts commercial standards Digital Video Broadcast-ing Satellite Second generation (DVB-S2) and Digital Video Broadcasting Return Channel via satellite (DVB-RCS) with some unclassified military unique waveform features. Herein is the ability to produce affordable modems for space and terminal systems by multiple industry vendors. The modem cost is anticipated to be lower than current costs because of competition from multiple vendors.

• PTW antijam modems can replace current wideband, nonhopping modems, and can provide antijam capabil-ity to current wideband terminals or commercial termi-nals through modem swaps, which is an affordable way forward in the near term.

• It can be used for future high-capacity, antijam protected theater tactical satellites or hosted payloads for specific missions including RPA, manpack terminals for special forces requiring antijam capabilities, and for low-prob-ability interception (LPI) and low-probability detection (LPD). To provide antijam protection against many different

threats, the waveform uses low forward-error correcting (FEC) code rates along with channel interleaving, which offers robust communication against partial-band and partial-time jammers.

The waveform allows for terminals to be operated by unclassified personnel, as well as enabling forward de-ployment of PTW terminals. The waveform defines the controlled messages between terminal modem and termi-nal end cryptographic unit (ECU), which will allow all of the classified information to be self-contained within the terminal ECU during operations.

The waveform uses random frequency and time for se-cure transmissions of information. A table-based, National Security Agency (NSA)–certified, transmission security (TRANSEC) algorithm employed in PTW allows a group of terminals to share the same table with frequent system refresh. The separation of multiple PUGs can provide more security features and keep any impact to the mission to a minimum. The rekey capability to a small set of terminals can speed up operations recovery and simplify mission management.

It is essential for the waveform to support many types of space system communication platforms ranging from terminals operating at a disadvantage because of limited transmission power, or those with low-data-rate needs, to terminals that demand high-data-rate links. The new wave-form, on the return link (uplink) from terminals to space/hub, uses low-order modulation with low FEC code rates to support terminals with low-data-rate needs, and high-order modulation with high FEC code rates to support terminals with high-data-rate demands. The forward links from space/hub to terminals will be time-shared among several receiving terminals; therefore, modes with high throughput have been defined.

Aerospace has performed extensive simulation and actively participated in the PTW working group, provid-ing significant technical inputs in performance analysis for robust antijam capability, acquisition and tracking for terminal log onto the system, dynamic resource allocation (DRA) for efficient resource usage, and mobility protocols for seamless beam handover. Aerospace engineers reviewed 83 PTW change proposals from the contractor community, other FFRDCs, and TPOs; provided feedback to the gov-ernment; and participated in the voting process. The rigor-ous PTW change proposal process ensured the waveform is mature. The contractors, who have already implemented part of PTW for the space and terminal modems, have now endorsed it.

The PTW provides return link data rates ranging from 21.6 kilobits per second to 137 megabits per second, sup-porting a variety of terminal platforms and applications. Small and disadvantaged terminals such as manpack termi-nals with limited transmission power can use the low-data-rate modes (21.6 kilobits per second) to achieve fair-quality voice communication with LPI and LPD features. Certain tactical missions such as RPA require antijam protection at high-data-rate (137 megabits per second) links to transmit high-quality image data, which is 17 times higher than that of current protected systems.

In an effort to broaden future competition and the in-dustrial base for this new waveform, commercial waveform standards, including DVB, in particular DVB-RCS and DVB-S2, are used to provide definitions for the communi-cation modes. These standards have been in use by the sat-


ellite communications industry for more than a decade and the technology is mature. The performance characteristics of the modulation types and the FEC codes are well under-stood. Moreover, commercial off-the-shelf (COTS) hardware implementations are widely available. Adopting these stan-dards will help expand the industrial base for MILSATCOM, as well as reduce the development risk of the PTW, which is very important in achieving cost savings.

The current protected waveform uses a static resource al-location approach. In this design, the satellite resource usage is constrained, because it is set up as a circuit that meets the strategic user requirement for guaranteed service through dedicated lines. The PTW uses DRA, which is optimal for efficiency and maximizes the system throughput. The DRA will be performed by the system controller, who can origi-nate the resource changes from the satellite (for processed satellites), or from the ground hub (for transponder satel-lites), depending on the system architecture. This dynamic allocation style is capable of performing the appropriate communication mode selection, time, and bandwidth as-

signments based on link conditions and traffic requests. For example, the data rate can be dynamically reduced from 8 to 1 megabits per second if severe weather or jamming is en-countered, or can maintain 8 megabits per second by assign-ing more resources on the satellite or ground hub as needed.

Another important feature of the PTW is that it provides seamless support to mobile terminals. Typically, multibeam antennas for satellite payload designs are used to increase antijam protection in a theater coverage area. Extensive acquisition and beam handover protocols have been defined to facilitate seamless communication when mobile terminals (PCOTM and RPA) are moving out of the serving beam and into another beam without interruption of communication.

Protected Tactical Service System Concepts

The Space/Hub

There are four major types of MILSATCOM system architec-tures: hub-spoke pure transponder (PT), hub-spoke dehop/rehop transponder (DRT), partially processed (PP), and fully

Virtualpayload

Teleport orgateway

Ground connectivityNetwork connectivity

No crosslinks.Ground gateway for

interconnectivity

AEHF

Crosslink

Virtualpayload

Teleport orgateway

• Comparable antijamming capability

Affordable protected system features:

• Supports multiple satellite architectures (transponder, DRT, partially processed, and fully processed)

• Unclassified waveform (information assurance, suite B crypto) • Low-cost terminal• Simpler payload (or processing moved to ground)• Simpler mission planning and management• No crosslinks• Reliable mobile communication

• High-connectivity, user

Notional Protected Tactical Service Concept

Global information grid

Backupmission

planning/management

Low-costmission

planning/management

Unclassified waveform

Protectedtactical

waveform terminals

A notional protected tactical service concept that supports multiple satellite archi-tectures.

Protected tacticalsatellite

Commercial transpondersatellite

-to-user and user-to–global information grid


processed (FP) systems. Each of these satellite system ar-chitectures offers pros and cons. For example, conventional PT systems are simply “bent pipe” payloads—they convert uplink carrier frequencies to downlink carrier frequencies for transmission of information without offering onboard processing, such as demodulating and/or decoding for the received uplink transmissions.

Aerospace has developed government reference archi-tectures (GRAs) of four types of payloads and the protected tactical service (PTS) system concept, created various scenarios (theater, dispersed, jamming, and mobility) to evaluate multiple system designs, developed requirements for broad agency announcement studies, provided capacity analysis of GRAs against the benign and contested scenarios to perform system trade-offs, provided technical direction to space contractors, and reviewed contractor payload designs and performance analysis. The three space contractors work-ing this effort provided useful and multiple design concepts with affordable cost estimates. The U.S. government is now us-ing this technical and cost information to support the current Department of Defense MILSATCOM alternative of analysis.

In the PT architecture the satellite cannot perform chan-nelization and routing of information without incurring the heavy weight and high-power consumption of analog and digital components. To offset this, a ground hub is used in a

double-hop transmission mode to perform various virtual payload functions, such as routing, channelization, demodu-lation, forward-error-correction decoding, retransmission, dynamic resource allocation, and hub assistance for disad-vantaged user terminals. A source-user terminal sends traffic back to the hub via the return link (user-to-satellite-to-hub) where routing is applied and retransmitted using the forward link (hub-to-satellite-to-user) in a second hop transmission that travels over the bent-pipe payload and onto the desti-nation user terminal(s). This hub-spoke–type architecture requires a double-hop delay for user-to-user communica-tions. Normally, a commercial PT system will not provide antijam capability. However, this traditional, nonhopping modem can be replaced by a PTW modem with antijam functionality. The terminal can then resist the mobile and/or transportable jammer. This solution is the most affordable way to provide antijam capability to today’s wideband users because the new modems are not expensive.

In the PT architecture, since the bent pipe repeater translates the full frequency hop transponder bandwidth from the uplink to the downlink frequency band, retrans-mission of the received uplink signals includes any jamming, if present. A fraction of the downlink transmission power is then devoted to the retransmission of uplink jamming fall-ing within the transponder bandwidth, which is, in turn, a

Terminal 1Terminal 2

Antenna coverage areas

Gateway

Ground hub(virtual payload)

Net

wor

kin

terfa

ces

Timing unit Layer 2 switchingVirtual payload

System controller

Resource manager (DRA)

Mobility manager

Network manager

Encryption/decryption

TRANSEC

Base

band

pro

cess

ing

Hub

ante

nnas d

Transponder Satellite Architecture

Global information

grid

A notional hub-spoke dehop/rehop transponder architecture.

RF fr

ont e

n


power-robbing effect. Thus, the tolerable jammer power level of the PT architecture is limited by power loss.

In DRT, the uplink frequency hop is dehopped and filtered to a desired signal bandwidth that is much more narrow than the hopping bandwidth and is then rehopped for the down-link frequency translation. There are two purposes for this filtering effect: first, only that portion of the uplink jamming falling within the transponder bandwidth is retransmitted with the desired signal on the downlink; second, the filtering operation provides noise rejection prior to amplification. The DRT architecture requires a ground hub similar to the hub-spoke PT architecture. The main advantage of a DRT payload over a PT payload is improvement in antijam capabilities and spectrum use without multiple ground hubs.

An FP payload is an architecture in which uplink signals are dehopped, demodulated, and decoded on the satellite. Onboard digital processing is then performed by the system controller within the payload, which enables capabilities such as network resource allocation, control and packet switching, and routing. The downlink signals to user ter-minals are re-encoded, remodulated, and rehopped on the satellite for transmission.

In the FP architecture, the uplink and downlink FEC and modulations need not be the same, thereby enabling adap-tive dynamic resource power and bandwidth allocation. This is a single-hop architecture that does not require the use of a terrestrial hub because the system controller is on board the satellite. This architecture style requires a payload with com-plex on board digital processing capabilities. The fully pro-cessed payload terminates the uplink at the payload. Thus, it can eliminate any uplink jammer power-robbing effect present in the transponder. Moreover, the fully processed payload provides increases in satellite capacity compared to the traditional satellite transponder approach without the hub-spoke architecture, while providing true full-mesh single-hop multicast connections across all user terminals. The fully processed payload is also superior in terms of re-siliency, connectivity, and antijamming in comparison to the hub-spoke transponder-based approaches.

The PP architecture is intermediate in complexity between the single-hop fully processed payload and the double-hop transponder payload. In a PP payload, the up-link signal is dehopped and demodulated, but FEC does not occur. The signal is decoded, remodulated, and rehopped for downlink transmission. The cost difference between a PP and FP payload is negligible; however, a PP payload cannot provide the extensive network flexibility and performance of a FP architecture.

Different system architectures provide different levels of protection, capacity, and cost. The four communication architectures described can be implemented on free-flyers and/or on hosted payloads depending on mission require-ments. For example, the FP payload may be selected for missions requiring defeating a large jammer. A DRT, on the

other hand, may be selected because of user desire to defeat a transportable jammer.

A key feature of PTW is that it is agnostic to different satellite communication system architectures with common enterprise ground network infrastructures. This unique PTW feature makes it interoperable for different protected tactical users and their various system architectures and flexible to different mission requirements. The PTW system can be built over many years, delivering incremental capability, perfor-mance, and protection. This approach offers an innovative and revolutionary solution for future MILSATCOM systems.

Terminal TransitionPTW is designed to be coupled with the mature current protected waveform and existing commercial standards, therefore allowing all of the contractors (space and termi-nal) to be able to produce brass board modems with PTW functions within 10 months of contract start time in Phase I. Boeing has demonstrated multiple channel functions using PTW modems over a ViaSat Ka-band transponder satel-lite and WGS. L3 Communication West has successfully demonstrated the key features of PTW modems over Intelsat (Galaxy 18). Raytheon has demonstrated the PTW modem over WGS satellites using Navy terminals.

The architecture-independent nature of the new wave-form allows for its use over existing commercial and military transponded satellites. This means existing unprotected terminals could achieve a good level of protection over the same satellites they use today by swapping out their current modem with a PTW modem. Technically, one could put a PTW modem in a wideband terminal or commercial termi-nal and enable the use of PTW, and its associated protection, over a wideband or commercial satellite.

The majority of the terminal cost is in the radio frequen-cy components. This study effort has shown that the modem cost is about 6 percent of the total terminal cost. Therefore, the most affordable near-term way to acquire antijam capa-bility is via modem swapping from nonhopping modems to PTW antijam modems. The Air Force, Army, and Navy are interested in the modem swaps to avoid costly new terminal development. Because the PTW is frequency agnostic, it can also be extended to the extremely high frequency (EHF) band (two gigahertz hopping bandwidth instead of one gigahertz in Ka) in the future. This will reduce the problem of satellite and terminal programs not being synchronized. The terminal transition from commercial Ku band to high- bandwidth Ka band or from military Ka band to EHF will be much smoother too.

Ground Gateway and Network DevelopmentOne recurring theme of improving affordability of protected tactical MILSATCOM is the careful consideration of the trade-offs associated with allocating functions between space and ground systems. Offering functionality that uses ground


components may improve affordability because size, weight, and power constraints are not the concern that they are on systems that need to function in space; nor are space-hardened components needed on ground systems. There is also more ready availability of off-the-shelf components for ground systems.

Another substantial consideration relates to the support of current users on future systems, that is, backward compat-ibility. Here, one promising approach moves some of the current functions in space to the ground via the use of a set of gateway facilities.

A gateway of this type must provide secure and reliable connectivity between protected tactical MILSATCOM users and other networks. These networks include the Defense Information Systems Network (DISN); services and connec-tions with Advanced Extremely High Frequency (AEHF) users; and interconnections with other tactical service networks, such as the Army’s Warfighter Information Net-work–Tactical (WIN-T), and the Navy’s Automated Digital Network System (ADNS).

Thus, the interfaces of the gateway must dovetail with the operational requirements of existing systems, as well as with their various approaches to information assurance. Like the other segments of the system, the gateway must interface with a management system, as well as implement appropri-ate information assurance controls for its own operations.

One approach to developing the gateway interface in-volves using a diverse set of networks that employ Internet Protocol (IP) as a common denominator. Increasingly, mili-tary networks are in fact IP networks, and these networks have established approaches to information assurance for the transfer of their communications. Indeed, the gateway should be able to reuse these approaches if the satellite com-munications services provided allow for interconnection of a user’s IP equipment. For example, a satellite service provid-ing transit of a layer two-packet switch would support this type of interconnection across a wide variety of networks.

In this concept, the gateway system is largely reduced to an integration of off-the-shelf equipment, provided for and operated by individual users. In other words, it is a “bring- your-own-router” approach to the gateway interface. While this concept appears promising, the ultimate design must be considered across many factors, including packet overhead, applicability of off-the-shelf components, security consid-erations, and support for advanced services, such as traffic management, mobility, and efficient multicasting.

Mission ManagementThe Mission Management Subsystem (MMS) encompasses all of the operational and logistical functions needed to manage protected tactical MILSATCOM. These include communications planning, network management, satellite and mission operations, and monitoring, as well as support

to any training and maintenance activities. Here, the approach to affordability relies on integrating

commercial-like tools and processes into a MILSATCOM regime. This includes employing commercial and industry standards, tools, operational practices, and approaches to development across the entire lifecycle of the system. More-over, the approach must reconcile these established practices with the need to provide some level of consistency with cur-rent and projected MILSATCOM processes.

The operation supports standards of the Telecomm Management (TM) Forum, which offers a potential set of industry standards around which MMS functions could be built. TM Forum is a nonprofit organization that brings together the world’s largest service providers, network opera-tors, software suppliers, and system integrators. The TM standards complement the network management standards common to industry networks, e.g., those developed by the Internet Engineering Task Force (IETF). Nevertheless, unlike IETF standards, TM Forum standards do not ensure technological compatibility. Instead, the standards codify business processes, information models, and operational support functions. Using these standards could help in the development of consistent requirements with semantics well understood by a broad section of industry.

While use of off-the-shelf components undoubtedly reduc-es development costs, a future MMS will likely require some amount of software development and tailoring for adequate interface with the diverse set of MILSATCOM user communi-ties. Here, the ability to perform integration activities early on, and to sufficiently manage relationships with off-the-shelf vendors, will play a critical role during development.

Information Assurance The information assurance needs of protected tactical ser-vices must account for a diverse set of users who will operate with varying types of information protection requirements. The security requirements for next-generation protected tactical services have been derived from an analysis of many user scenarios, including those required by the Army’s PCOTM and at the halt (ATH) systems, the Air Force’s remotely piloted aircraft, Navy ships and submarines, and special operations forces.

The terminal cryptographic implementation is another essential element of the new protected tactical services and provides the basis for the frequency hopping from which these services enjoy antijam capabilities. Further, the crypto-graphic implementation provides the basis for the transmis-sion security cover function, which is used for traffic flow and is part of the terminal logon requirement. Much atten-tion has been focused on the cryptographic implementation, with particular interest in the Army PCOTM terminal end cryptographic unit (ECU).

The terminal ECU is particularly interesting because its


requirements are somewhat unique. The Army Terminal Program Office has stated it wants a completely unclassi-fied while operating terminal. Meanwhile, other users have requirements for the ECU to be operated with secret-level transmission security key material. This leads to the unique requirements of keyed at secret, yet operational at unclassi-fied. This may be attained through the use of current crypto-graphic certification processes. A successful implementation here will likely be a pathfinder for future efforts wanting the same results.

The PTW is envisioned to be similar to other national security systems in that it will likely be subjected to cyberattack. It is anticipated that the PTW will be developed and operated consistent with the security controls specified for other DOD systems.

ConclusionSince late 2011, the MILSATCOM community (the govern-ment, FFRDCs, TPOs, and contractors) have made good progress toward the goal of developing new concepts for future PTS systems that will meet warfighters’ needs identi-fied in JSCL for performance and protection in the contested environment while remaining affordable.

Aerospace has assisted the U.S. government in achiev-ing these goals and has been a significant technical leader and contributor in developing PTW requirements; GRA designs of the space, ground, gateway, and mission manage-

ment subsystems; and network and information assurance architectures.

Aerospace has provided in-depth technical analysis and directions to the MILSATCOM community and to contrac-tors during the latest phase of the study, and has assisted the U.S. government in establishing the future acquisition strategy of PTS.

The contractors have successfully completed PTW com-patibility testing at the Massachusetts Institute of Technol-ogy/Lincoln Labs in July/August 2014 and three contractors (Boeing, L3 Communication West, and Raytheon) have already successfully performed over-the-air testing, proving that PTW is the future waveform for tactical missions.

AcknowledgementsThe authors would like to thank Tom Hopp, Robert Liang, Steve Schmidt, James Stepanek, and Milton Sue for their contributions to this article.

An example of a DRT satellite architecture.

• Uplink:

DRT Satellite Architecture Dehop/rehop transponder

Return link

Forward link

Three gimbal dishantennae coverages

Earth coverage antenna

Hub/gateway

Ground processor

Network interfaces

Globalinformation

grid

Hub/gateway Dual polarization

(1 GHz super high frequency bandwidth on each polarization)

2 GHz extremely high frequency bandwitdth

User terminal

Terminals with frequency hoppingUplink: 2 GHz extremely high frequency bandwidthDownlink: 1 GHz super high frequency bandwidth

Missionmanagement

system General operationsmanager

PTS unique

shared

Satellite and gatewaycontroller

Theater antenna coverage

• Downlink:


Applying Systems Engineering to Manage U.S. Nuclear CapabilitiesThe Aerospace Corporation’s expertise in program systems engineering and integration is being applied to

nuclear programs for the National Nuclear Security Administration.

Matthew J. Hart, James D. Johansen, and Mark J. Rokey


The National Nuclear Security Administration (NNSA) ensures the United States sustains a safe, secure, and effective nuclear deterrent. Through the Office of

Defense Programs, the mission of the Stockpile Steward-ship and Management Program is to maintain the active stockpile, extending the life of weapons systems through the application of science, technology, engineering, manufac-turing, and weapons dismantlement. Through the Office of Defense Nuclear Nonproliferation, the NNSA works closely with laboratories and the private sector to detect, secure, and dispose of dangerous nuclear and radiological material, and related weapons of mass destruction (WMD) technology and expertise.

The U.S. Congress created the NNSA in 2000 as a sepa-rately organized agency within the Department of Energy, responsible for the management and security of the nation’s nuclear weapons, nuclear nonproliferation, and naval reactor programs. In 2002 the NNSA reorganized, removing a layer of management by eliminating its regional operations offices in New Mexico, California, and Nevada. NNSA headquarters retained responsibility for strategic and program planning, budgeting, and oversight of research, development, and non-proliferation activities. More recently, the NNSA requested that The Aerospace Corporation conduct an external and independent review of its management practices, systems engineering, and mission assurance in a number of impor-tant areas.

When Aerospace was founded in 1960, its initial contract was with the Air Force Ballistic Missiles Division, supporting the development of advanced nuclear missile technologies and missile defense programs. During the 1970s and 1980s, Aerospace had important roles in planning major infrastruc-ture and technology projects for the Department of Energy. Many of the technologies found in spacecraft and launch vehicles are also commonly used by the nuclear security enterprise. Aerospace has remained active in these areas and continues to support them today.

Office of Defense ProgramsIn 2011 Aerospace conducted a series of independent stud-ies, at the request of Defense Programs, focusing on the systems engineering and mission assurance management processes applied to its major nuclear weapons refurbish-ment programs, known as life-extension programs. The NNSA employs an end-to-end acquisition process, referred to as the Phase 6.X Process, which differs in some ways from DOD acquisition practices. Moreover, the relationship between the NNSA, as a partner with the nuclear weapons laboratories and production sites, differs from that of the government customer-prime contractor relationship that exists for DOD acquisitions. In light of these differences, Aerospace approached this task by taking a fresh look at the NNSA’s way of doing business and provided value-added

observations and recommendations within the context of the existing NNSA acquisition culture and structures.

Aerospace assembled a team of senior personnel with knowledge of complex systems acquisition and development, systems engineering, integrated lifecycle management, mis-sion assurance, and program execution. The team focused on five areas: staffing and workforce, cost and schedule estimat-ing, budget management, technology and manufacturing, and program systems engineering and risk management. The team interviewed key NNSA federal managers and staff, and personnel at the national laboratories and production sites across the nation. The team also interviewed DOD stake-holders within the Navy and Air Force. The team reviewed programmatic and technical information from the site visits, NNSA-provided information, and other government reports and audits.

The Aerospace report focused on the need for an orga-nizationally independent systems engineering and integra-tion (SE&I) function at the enterprise level to help manage requirements, provide technical insight, and support the consistent use of best practices across the enterprise. Other recommendations were made, including formalizing the decision process for mitigating risk and establishing a strong technical and programmatic baseline management process for NNSA acquisition programs.

The report helped the Office of Defense Programs to make decisions on reorganizing and creating two new groups. One group would focus on major acquisitions, such as weapons life extension programs, and the other would provide the independent SE&I function. Aerospace assisted in identifying candidate SE&I organizational structures, roles and responsibilities, and staffing requirements.

Today, Aerospace is providing experienced engineering advisory support to the Defense Programs SE&I in Wash-ington, D.C., and Albuquerque, New Mexico, which includes program systems engineering for the B61 gravity bomb life-extension program, independent technical studies and risk assessments, and the development of systems engineering policy and practices to benefit the enterprise.

• Defense programs: maintain a safe, secure, and reliable nuclear weapons stockpile to help ensure the security of the U.S. and its allies, deter aggression, and support international stability.

• Defense nuclear nonproliferation: detect, prevent, and reverse the proliferation of weapons of mass destruction and promote international nuclear safety.

• Naval reactors: provide the U.S. Navy with safe and effective nuclear propulsion systems and ensure their continued safe and reliable operation.

• Emergency operations: manage nuclear and radiological emergency response capabilities within the U.S. and abroad.

The National Nuclear Security Administration’s mission areas.


Source Evaluation BoardThe nation’s nuclear weapons laboratories are managed, on behalf of the NNSA, through management and operating (M&O) contracts to large private sector companies, universi-ties, and nonprofit organizations. As part of the work in re-viewing NNSA management processes, Aerospace was asked to review and comment on the current M&O contract-ing strategy. The Aerospace team met with NNSA source evaluation board representatives and gathered background information on the agency’s current contracting and source selection approach, and supporting documents and example artifacts from previous competitions.

The study team provided the NNSA source evaluation board with information on acquisition strategy best prac-tices, such as structuring statements of work, contractual deliverables, and invoices to manage contractor performance and ensure access to technical and programmatic informa-tion needed to monitor contract performance.

Office of Defense Nuclear Nonproliferation Research and DevelopmentOne of the gravest threats the United States and the inter-national community face is the possibility that terrorists or rogue nations will acquire nuclear weapons or other WMDs. NNSA’s Office of Defense Nuclear Nonproliferation Research and Development supports the multiagency United States

Nuclear Detonation Detection System (USNDS) in detecting nuclear detonations around the world. The office supports this effort through research and the development of space-based sensors to monitor for nuclear events and provide global awareness of possible nuclear detonations.

The USNDS sensors are hosted on military satellite systems managed by the Air Force, such as the Global Posi-tioning System (GPS). As these satellites undergo planned block upgrades or transition to other programs, the effects of such changes on the USNDS mission must be considered. The Office of Defense Nuclear Nonproliferation Research and Development conducted an analysis of alternatives to assess future USNDS sensor architecture alternatives, which considered different numbers and types of sensors and next-generation sensor technologies and their impact on cost, schedule, and performance.

The office asked Aerospace to participate as an indepen-dent third party to provide independent cost and schedule assessments, risk assessments, and technical advice con-cerning systems architecture, host spacecraft, and sensor technology. Aerospace’s extensive knowledge of the host spacecraft allowed a deeper understanding of the technical and program implications of the different sensor alternatives and their risks to USNDS and the host missions.

Aerospace brought in experts knowledgeable in the host space systems and spacecraft requirements to confirm key assumptions in the study. Aerospace helped the NNSA understand the system drivers on the current host platforms and constellations and the effect that changing spacecraft requirements would have on the sensor designs. The host spacecraft’s planned availability date was also important in defining the development times and need dates for a new sensor. Aerospace applied the cost and schedule estimating methodology developed for assessing NASA science instru-ments to estimate the development and production costs and readiness dates for the alternative sensor architecture options.

Aerospace’s analysis provided the Office of Defense Nuclear Nonproliferation Research and Development with information on the cost and availability of the different architecture options. This was combined with system and

The phase 6.X process that the National Nuclear Security Administration uses to manage life-extension programs for the United States nuclear weapons stockpile.

The Space-based Nuclear Detonation Detection mission is supported with hosted payloads on Air Force satellites, such as GPS.


architecture performance assessments to help the office select affordable future architectures that meet operational requirements and stakeholder needs.

The Office of Defense Nuclear Nonproliferation Research and Development identified the need for an independent architecture-level simulation capability to predict system performance so that it could assess current and next-generation USNDS systems’ ability to meet requirements. The Distributed Infrastructure Offering Real-time Access to Modeling and Analysis (DIORAMA) software tool will provide a robust physics-based modeling and simulation capability and will be validated, well documented, and acces-sible for use by the entire USNDS community.

NNSA has asked Aerospace to colead the independent verification, validation, and accreditation effort of DIORA-MA, along with Lawrence Livermore National Laboratory, and the Air Force Institute of Technology.

The verification component will determine if DIORA-MA’s modeling and simulation implementation and its associated data accurately represent the software developer’s conceptual descriptions and specifications. The validation component will determine if the performance model and its associated data provide an accurate representation of the real world from the perspective of its intended uses—in this case, detecting nuclear detonations and processing detection data. As part of this effort, the team will monitor the development of test plans, develop independent system scenario testing, and monitor regression testing as functional capabilities are

added and the software matures.Accreditation will be official certification that the per-

formance model and its associated data are acceptable for use by NNSA and its affiliates. Accreditation also certifies that the software has met all requirements and performance specifications, along with security concerns and maintain-ability. This accreditation will be based on the integration of verification and validation findings that will be delivered and reviewed throughout the software development lifecycle.

As part of the NNSA’s ongoing efforts to improve overall performance, the Office of Defense Nuclear Nonproliferation Research and Development has established its own inde-pendent SE&I functions to provide systems engineering and mission assurance support to the office’s sensor development activities. Aerospace is providing independent technical and programmatic advice, risk assessments, and subject matter expertise to aid in resolving technical problems during the development process.

ConclusionSupport to the NNSA demonstrates the application of Aero-space technical and acquisition know-how to the broader national security enterprise. Aerospace’s ability to offer sound, unbiased technical advice, and apply its program-matic expertise to complex acquisition problems, provides benefits to the government that go beyond national security space.

A timeline of nuclear weapons development and historical information.

Courtesy of NN

SA and the National Archives


Strained Silicon Photonic Devices for Optical Modulation

The demand for compact, low-cost components for optical communication, signal processing, and optical sensing is driving the rapid development of silicon photonics. Silicon is a chemical element used in semiconductor electronics and integrated circuits and is the basis of most of today’s comput-ers. Crystalline silicon can also be used to make photonic components and can be used to integrate electronics with photonic functionality on a single chip-scale platform. Most of today’s optical systems rely on discrete optical fiber components or free-space optical elements. However, these components take up a lot of space, therefore limiting the overall capacity and functionality that can be engineered into a small volume. National security space applications will benefit from the development of next-generation inte-grated high-speed optoelectronic circuitry based on silicon. The benefits of using silicon components on these systems include increased bandwidth capability, smaller physical footprints, and reduced power consumption.

A key building block in any photonic system is the electro-optical modulator, an optical waveguide device that imprints an electrical waveform or data stream onto an optical carrier. Analog waveforms or data bits may be encoded by shifting the amplitude or phase of the light that passes through it with this device. The phase or amplitude shifts are generated by the ap-plied input electrical waveform that alters the refractive index of the modulator material (electro-optic effect). Because of the cubic symmetry of the silicon crystal lattice, however, this ma-terial does not naturally exhibit this effect. Other techniques, such as charge-carrier depletion and thermo-optic tuning, have been used to modulate the refractive index of silicon, but

these have limited data bandwidth capabilities and consume excessive electrical power.

By introducing strain into the silicon crystal structure, silicon can exhibit electro-optic activity. Aerospace research-ers are exploring this strained silicon approach. Andrew Stapleton, a member of the technical staff, Photonics Technol-ogy Department, is the principal investigator of a team that is using strained silicon to make electro-optical modulators. The research team includes Peter DeVore, Heinrich Muller, and Todd Rose, all of the Photonics Technology Department. These team members have supported several national security space programs in which lithium niobate optical modulators have been used. The team is applying findings from this work to its research into silicon straining techniques. The research-ers have found that the silicon modulators they are developing do not appear to degrade in the space environment, unlike lithium niobate modulators, which are currently being used for this application.

To achieve strain in silicon waveguides, a thin layer of silicon dioxide is deposited over the crystalline silicon optical waveguides. The strained silicon modulators are fabricated at Aerospace with commercially available silicon-on-insulator wafer substrates. These wafers have a 0.26-micrometer-thick silicon device layer over a 2.0-micrometer layer of silicon di-oxide. A thicker, silicon substrate lies under the oxide. The top silicon layer is sufficiently thin to support a single transverse optical mode of light at a wavelength of 1.5 micrometers. Be-fore depositing the dielectric straining layer onto the device, the waveguide patterns are first defined in a photoresist mask on top of the wafer substrates. Then, a sulfur hexafluoride plasma etching process is used to transfer the waveguide

RESEARCH HORIZONS Independent R&D at Aerospace

Scanning electron microscope image of a cross section of the device showing a one micrometer wide buried silicon waveguide.

Si phase modulator response

Applied voltage (V )pp

Phas

e re

spon

se (r

adia

ns)

1.2

1.0

0.8

0.6

0.4

0.2

0.0

05 0 100 150 200 250

Phase response of a strained silicon modulator.


patterns from the mask to the underlying silicon layer, and the photoresist mask is removed. Once the optical device layer is fabricated, a 1.5-mi-crometer silicon dioxide top layer is deposited in a plasma-enhanced chemical vapor system at 300 degrees Celsius. Because of the difference between the coefficients of thermal expansion for silicon and silicon dioxide, the silicon waveguide core is strained as the structure cools to room temperature.

Because strain distorts the silicon crystal lattice’s symmetry, strained silicon exhibits an electro-optic effect so that the index of refraction of the crystal waveguide, and hence the phase of the transmitted light, can be controlled with an applied electric field. “The first experiments in-volved simple optical phase modulators in which gold electrodes were deposited on the waveguide samples,” said Stapleton. The researchers placed the silicon modulators in a free-space optical interferometer, quantifying the optical phase change under various voltages. This technique al-lows for estimating the strained silicon’s nonlinear susceptibility, a key performance metric.

Numerical simulations using COMSOL (a software pro-gram for modeling and simulating scientific and engineer-ing problems) indicate that 2.5 percent of the total voltage was applied across the silicon waveguide, with the bulk of the voltage dropped across the electrically insulating oxide above and below the waveguide core. From this analysis, the nonlinear susceptibility was estimated to be 2.7 picometers per volt. While this value is less than that of gallium arsenide or lithium niobate (99 and 360 picometers per volt, respec-tively), further improvement is expected if the magnitude of the strain in the waveguide can be increased.

For this reason, the Aerospace research team has been working to understand and quantify strain in fabricated devices under various waveguide geometries and process-ing conditions. One analytical technique being used is micro-Raman spectroscopy. In this technique, light from a blue laser is focused on the waveguide sample, exciting the silicon crystal lattice’s optical phonon modes. The scattered light emitted from the sample surface is then collected and analyzed under a microscope. Unstrained silicon has a dis-tinct characteristic Raman peak at 520 waves per centimeter. When the analyzed sample is a strained silicon waveguide, the Raman peak shifts to either a higher or lower wave num-ber (corresponding to compressive or tensile strain, respec-tively). The magnitude of this shift can be used to quantify the level of strain in the waveguide.

“The silicon waveguide samples studied with micro-Raman spectroscopy were found to be under tensile strain,” said Stapleton. Similar Raman data from other waveguides with different widths indicates that the magnitude of this strain increases as the width of the waveguide is reduced. For example, the strain in 0.5-micrometer-wide waveguides was approximately twice the strain observed in 1.0-micrometer-wide waveguides. These findings indicate that the electrical-to-optical conversion efficiency (i.e., gain) of strained silicon modulators can be significantly improved by fabricating devices with narrower waveguides.

In addition to developing a silicon optical phase modula-tor, the research team has demonstrated a fully integrated optical intensity modulator containing two strained silicon phase modulators along with waveguide splitters and com-biners in a Mach-Zehnder interferometer configuration. This demonstrates that strained silicon devices can be integrated with other optical components to form more complex opti-cal systems on a single chip.

While the development of strained silicon modulators is very much in its infancy, this approach points to the feasibil-ity of devices that are more chemically inert and tolerant of space environments compared to current state-of-the-art lithium niobate modulators. Further work will need to focus on improving the overall modulation efficiency of strained silicon modulators before this class of devices can be consid-ered a viable substitute.

RESEARCH HORIZONS Independent R&D at Aerospace

Raman spectra collected from a region of the unstrained silicon substrate (solid dots) and a one micrometer wide strained silicon waveguide (open dots). The lines are numeri-cal fits to a Lorentzian profile.


Toward a Better Understanding of Electrostatic Discharge

RESEARCH HORIZONS Independent R&D at Aerospace (continued)

If current spacecraft power trends toward increased solar ar-ray size and operating voltage continue, the risk of on-orbit performance losses from electrostatic discharge (ESD) will also increase. Without proper electrical charge mitigation, solar arrays and other satellite components are subject to significant charging in the space environment. Such charging can lead to substantial and frequent electrostatic discharge, which is a sudden flow of electricity between two differently charged objects, sometimes causing an on-orbit anomaly.

Spacecraft ESD is a complex phenomenon that can dis-rupt normal operations and even destroy solar array circuits and other electronics. Studies have been conducted since the 1970s to expand the awareness and understanding of these events, leading to the development of analysis tools such as NASCAP-2K (NASA/Air Force Research Laboratory [AFRL] spacecraft charging analysis program). This next-generation spacecraft charging analysis code can create realistic geo-metric models, simulate charging, and calculate and display surface potential/currents, space potentials, and particle trajectories.

As sophisticated as many of these analysis tools have become, they still lack some of the critical parameters and physics needed to make accurate predictions for ESD in the space environment. Decades of laboratory tests have at-tempted to establish electrical charge dynamics and propaga-tion, but there is limited consensus on the basic mechanisms and fundamental quantities of these effects, including propa-gation velocity, which helps to determine the magnitude of current transients. Spacecraft developers therefore continue to rely on the testing of components in a simulated space environment to create high-performance designs.

In an effort to develop more accurate prediction tech-niques, Jason Young, a member of the technical staff, and Mark Crofton, a senior scientist, both of the Propulsion Sci-ence Department at The Aerospace Corporation, have been conducting research to better understand the dynamics and scaling of electrostatic discharge on large satellite compo-nents, including solar arrays and multilayer insulation. They are using ESD1 for the testing, which is Aerospace’s new space-simulation vacuum facility, built to carry out electro-static discharge testing in a more optimized way (most of the historical Aerospace work was performed in the EP2 electric propulsion chamber).

“Although we know a great deal about how surface charge builds up on spacecraft components, many details of how that charge is released are uncertain. This makes it difficult to properly predict the shape, peak amplitude, and duration of the discharge current for array-size structures, which is

the ultimate determinant for risk of component damage or failure,” said Young.

Over the past several decades, the entrenched paradigm for electrostatic discharge has been the brushfire model. According to this model, an ESD current radiates outward at a constant speed from a single central arc point, instantly clearing all surface charge along the propagating front. As the electrical charge is cleared from dielectric surfaces like coverglass, currents are generated on adjacent conductors, like solar cells.

The brushfire model assumes the propagation of ESD occurs at a fixed speed that is independent of surface mor-phology or composition. However, experiments on complex test components that measure this propagation have often produced varied results.

Young and Crofton’s research has so far revealed that ESD is much more complicated than the findings of the brushfire model. Instead of using a complex, reduced-scale solar array coupon, which is the standard component for electrostatic discharge testing, the researchers have used a one-square-meter panel of concentric ring electrodes covered in Kapton, a polyimide film used in flexible printed circuits. The panel has been irradiated with electrons to create a net positive surface charge that is similar to conditions found in geo-synchronous Earth orbit during an extreme space weather event. Electrical arcs were generated from a defect at the test panel’s center, resulting in induced electrical currents on the ring electrodes.

“By measuring these currents, we could determine the ra-dial progression of an electrostatic discharge event. The data

View from end port of ESD1 vacuum chamber in D1. The US Round Robin Coupon from NASA GRC is mounted inside for inverted gradient charging tests.


show that instead of a sequential removal of charge from the innermost to outermost ring, charge removal begins on all rings nearly simultaneously, with the charge removal on more distant rings taking more time. The data also show that peak current amplitude is not proportional to ring radius, which is in contradiction to the brush fire theory,” said Young.

The researchers have also found that during an ESD event, electrical current grows more or less linearly with time, along with brief, intermittent increases and decreases of current rapidly propagating from inner to outer ring electrodes. Because of their proximity to the panel center and smaller surface area, the released charge fraction of inner ring electrodes changes more rapidly. As the remain-ing surface charge decreases, the electrode current declines exponentially.

“These characteristics of electrostatic discharge are remi-niscent of a diffusion process, which has important implica-tions for components operating in space. Since electrostatic discharge propagation has been found to be dispersive in these tests, a peak anomaly current does not necessarily increase linearly with distance, as was originally believed. In fact, it seems to increase more slowly, suggesting more favor-able scaling for large spacecraft components,” said Young.

Moving forward, Young and Crofton plan to introduce

more variations in the ring panel’s surface and morphology and the composition of the elec-trical arc initiation point. The re-searchers are hoping to correlate the ring electrode current pat-terns using external diagnostic instruments such as Langmuir probe arrays and imaging spec-trometers. Once these instru-ments are calibrated, they could then be transitioned to test more complex satellite components, such as solar array coupons and multilayer insulation sheets, in which the electrode patterns are not as optimized for measuring electrical current.

The Aerospace researchers are also participating in a series of tests with AFRL and other ESD researchers around the country. In similar setups at mul-tiple facilities, various solar array

coupon designs are being tested to measure ESD propaga-tion characteristics in simulated geosynchronous and low Earth orbit charging environments. The team is also working with a pulsed laser that can produce ESD on demand. Inter-estingly, the researchers have found that the ESDs produced at specific intervals by the laser varied more significantly in magnitude and duration than those produced spontaneously. This technique is anticipated to produce insights into ESD initiation thresholds and electrical arc rates.

Through the development and application of new ap-proaches like these, the team hopes to augment the current database and understanding of ESD in the space environ-ment, improve qualification test procedures, and reduce the risk of disruptive on-orbit ESD events.


Surface charge neutralization current for a single ESD event as a function of time and radial distance from inception point on the ring coupon. (Inset) Image of the Kapton-covered ring coupon.



Mobile Code and COAST: Potential Allies to Cybersecurity in the Cloud

Cloud computing presents an attractive option for hosting digital services where storage and computational demands may vary significantly over time. Computing clouds are elastic infrastructures that can be quickly expanded or contracted in response to variations in service demands or computational needs. These modern clouds rely on virtual machines to emulate the hardware and peripherals of physi-cal servers with multiple virtual machines executing on a single physical server. Modern large-scale clouds, offered by commercial vendors such as Amazon, Google, and Micro-soft, are provisioned on a massive scale. For example, the Amazon cloud is estimated to contain approximately 500,000 high-performance physical servers, and the Google cloud is believed to be significantly larger.

Government agencies can reduce costs by sharing a cloud with other organizations and users, while the cloud infrastructure transparently manages service load variations behind the scenes. Ample cloud computing and networking resources simplify the design, implementation, and deploy-ment of critical information services, while spikes in service demands can be accommodated within minutes. However, these resources and the flexibility they offer come with a price: this same massive cloud-computing infrastructure can launch cyberattacks against other information services within and outside the cloud.

Mobile code is a technology that allows the seamless transfer of running computations from one network loca-tion to another, or equivalently from one virtual machine to another, and therefore is an attractive complement to cloud-based virtual machines. Mobile code simplifies the construction and deployment of cloud-based services by allowing programs to be dynamically moved to different virtual machines as the cloud is expanded or contracted. In addition, services using mobile code can be deployed on the fly to modify or augment services in response to evolving missions or the immediate, urgent demands of a cyberattack.

However, due to its easy deployment and flexibility, mobile code is also a superlative tool for mounting attacks against a system. Thus the same mobile code technology that promotes system flexibility and adaptivity also puts systems at considerable risk. Can the benefits of mobile code technol-ogy be enjoyed without increasing the risk of a cyberattack? At a minimum, the mobile code and its supporting infra-structure must be secured against attack—a difficult and vexing problem for which no compelling solution has been articulated.

To counter these threats, Michael Gorlick, senior engi-neering specialist, Computer Systems Research Department,

and Richard Taylor, a professor of information and computer sciences at the University of California, Irvine, are investigat-ing mobile code options for securing against cyberattacks that arise from within the cloud. Gorlick and Taylor have developed COAST (COmputAtional State Transfer), an architecture style that is based on mobile code for Internet-scale network services where the mobile code itself becomes a critical element in a coordinated defense against cyberattacks.

“COAST is based on capability security, which fuses the designation of a service and access to that service into a single, unforgeable reference—a capability,” said Gorlick. The COAST architecture prescribes cloud-based mobile code systems with a set of simple yet powerful rules. It defines a set of mechanisms that allow programs to defend themselves against hostile or malicious visitors, halts communication with ill-behaved programs in the cloud or network, and pre-vents unrecognized programs from communicating directly with the COAST-based services residing within the cloud.

“COAST confines visiting mobile code with restrictive functional, resource, and communication capabilities, defin-ing what the mobile code can do, and limiting its resource consumption and communication powers. The visiting code has only the powers granted to it and nothing more,” said Gorlick. For example, if a program is not explicitly granted a capability to read a sensitive database, then it will not be allowed access to it.

COAST denotes individual programs with capability uniform resource locators (CURLs), which are the carri-ers for communication across a network. “These CURLs are cryptographic structures that are impossible for any other computation to guess, counterfeit, or modify without being caught,” said Gorlick. Programs within COAST rely on communication by introduction. For example, program X cannot communicate with program Y unless it holds a CURL explicitly allowing the communication. This commu-nication by introduction helps to ward off denial of service attacks, eliminates spurious communications, hinders theft of service, detects the misuse of communications, assigns blame, and revokes communication privileges as needed. CURLs also enforce communication constraints, including the total number of times that X can communicate with Y, the maximum rate and bandwidth at which X can communi-cate with Y, and the span of time during which the commu-nication is permitted. The mechanisms of mobile code can enforce complex communication constraints that implement temporal, spatial, and collaborative requirements.

Gorlick and Taylor have now implemented Motile, a



mobile code programming language consistent with the precepts of COAST, and Island, a decentralized, peering infrastructure capable of safely executing mobile Motile pro-grams. Motile/Island resolve the conundrum of safe mobile code by repeatedly applying capability security at all levels of a given infrastructure. The same capability security that pro-tects Island against errant or deliberately malicious Motile programs also protects the infrastructure itself from cyberattacks. Both the Motile compiler and the Island infrastruc-ture are written in Scheme, a programming language with a long history in mobile code experimentation. The Island infrastructure is the service-oriented architecture equivalent of service providers and consumers; a single “island” can simultaneously act as both a provider and consumer.

“By embedding specific mobile code into CURLs, we can ensure that whenever program Y attempts to exploit a capa-bility designated for program X, its effort will fail. Control-ling the propagation of capability among programs is critical to minimizing the risks of cyberattack, and mitigating the likely damage of an attack is a core element of our ongoing research,” said Gorlick.

Gorlick and Taylor are also exploring how COAST can be used in a variety of space settings and domains, including for the distribution and manipulation of high-bandwidth satellite telemetry. COASTcast, a demonstration applica-tion implemented with Motile/Island, permits users to view,

share, and manipulate real-time, high-definition satellite video streams. Their research suggests that COAST-based architectures are feasible in domains characterized by multiple, continuous data streams, including for satel-lite ground stations.

“One distinguishing characteristic of the COAST architectural style is its complete indifference to the actual location or precise for-mulation of mobile computa-tions. In particular, Motile/Island can execute on a broad scale of platforms and in a variety of network envi-ronments, from embedded single-board computers to a cloud of virtual machines,” said Gorlick.

Gorlick is also working with Larry Miller, principal en-gineering specialist, Software Engineering Subdivision, and David Wangerin, Computer Systems Research Department, to consider new spacecraft designs in which all spaceborne services, including payloads, are implemented in the COAST architectural style. The researchers have found that mobile code has the potential to simplify many troublesome aspects of spaceborne architectures, including autonomous fault recovery, hot updates (updating onboard software without pausing or rebooting), and processor failure.

For example, automated responses can simply abandon a processor if it fails, and by using mobile computations, reconstitute the services elsewhere within the spacecraft, on another nearby spacecraft, or perhaps (real-time constraints permitting) on the ground. A testbed infrastructure based on low-cost, single-board computers is now being constructed for prototyping common satellite bus subsystems such as thermal control, electrical power distribution, and attitude control. Here, the challenges include adapting COAST to the rigors of spaceborne systems, recasting traditional embedded designs for mobile computations, and ensuring the effective and timely execution of mobile computations on resource-constrained platforms.

Controlling the propagation of capability among programs is critical to minimizing the risks of cyberattack.


Publications _____________________________L. R. Abramowitz et al., “U.S. Air Force’s SMC/XR Space

Environmental NanoSat Experiment,” AIAA 2012 SPACE Conference and Exposition (Pasadena, CA, 2012).

W. A. Ailor, M. A. Weaver, et al., “Perspective on Reentry Breakup Recorder Derived Concepts for Small Payload Flight Experiments,” 44th AIAA Thermophysics Confer-ence (San Diego, 2013).

J. Alexander, J. Betser, L. Florer, J. Nilles, P. Reiher, et al., “Improving the Security of Android Inter-Component Communication,” Proceedings of the 2013 IFIP/IEEE International Symposium on Integrated Network Manage-ment, pp. 808−811 (Ghent, Belgium, 2013).

J. Bannister et al., “A Design for an Internet Router with a Digital Optical Data Plane,” Proceedings of SPIE—The International Society for Optical Engineering (2014).

J. Bannister et al., “An Optical Packet Switch Using Forward-Shift Switched Delay Lines,” 2013 18th OptoElectronics and Communications Conference Held Jointly with 2013 International Conference on Photonics in Switching (Kyoto, Japan, 2013).

J. D. Barrie, P. D. Fuqua, M. J. Meshishnek, M. R. Ciofalo, C. T. Chu, J. A. Chaney, R. M. Moision, et al., “Root Cause Determination of On-Orbit Degradation of the VIIRS Rotating Telescope Assembly,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

P. A. Bertrand, “Chemical Degradation of a Multiply Alkyl-ated Cyclopentane (MAC) Oil during Wear: Implications for Spacecraft Attitude Control System Bearings,” Tribol-ogy Letters, Vol. 49, No. 2, pp. 357−370 (2013).

J. Betser et al., “Innovation Acceleration for National Secu-rity Space,” AIAA 2012 SPACE Conference and Exposition (Pasadena, CA, 2012).

J. Betser et al., “Knowledge Management for Architecting Space Systems,” AIAA 2012 SPACE Conference and Expo-sition (Pasadena, CA, 2012).

J. Betser et al., “Managing the Next Wave of Information and Communications Technologies: A Report on NOMS 2012,” Journal of Network and Systems Management, Vol. 21, No. 3, pp. 510−516 (2013).

J. Betser et al., “Space Cyber Architecting Horizons,” AIAA 2012 SPACE Conference and Exposition (Pasadena, CA, 2012).

J. Betser, K. Ferrone, G. Richardson, J. Penn, and S. Mar-tinelli, “On-Orbit Servicing of Department of Defense and National Security Space Assets,” AIAA 2012 SPACE Conference and Exposition (Pasadena, CA, 2012).

R. Bishop et al., “GEOScan: A Global, Real-Time Geoscience Facility,” IEEE Aerospace Conference Proceedings (Big Sky,

MT, 2013).

R. Bishop, A. Christensen, J. Hecht, et al., “The HICO RAIDS Experiment Payload Mission,” Proceedings of the 1st Annual ISS Research and Development Conference (San Diego, 2013).

R. L. Bishop et al., “Propagation of CubeSats in LEO Using NORAD Two Line Element Sets: Accuracy and Update Frequency,” AIAA Guidance, Navigation, and Control (GNC) Conference (Boston, 2013).

R. L. Bishop, J. H. Hecht, R. W. Walterscheid, et al., “Alti-tude Profiles of Lower Thermospheric Temperature from RAIDS/NIRS and TIMED/SABER Remote Sensing Ex-periments,” Journal of Geophysical Research: Space Physics, Vol. 118, No. 6, pp. 976−982 (2013).

R. Bitten, D. Emmons, F. Bordi, et al., “Explanation of Change (EoC) Study: Approach and Findings,” IEEE Aerospace Conference Proceedings (Big Sky, MT, 2013).

R. Bitten, D. Emmons, M. Hart, F. Bordi, et al., “Explanation of Change (EoC) Study: Considerations and Implementa-tion Challenges,” IEEE Aerospace Conference Proceedings (Big Sky, MT, 2013).

R. Bitten, E. Mahr, et al., “Assessing the Benefits of NASA Category 3, Low Cost Class C/D Missions,” IEEE Aero-space Conference Proceedings (Big Sky, MT, 2013).

R. E. Bitten, D. L. Emmons, F. Bordi, M. J. Hart, et al., “Find-ings and Considerations from the NASA Explanation of Change Study,” AIAA SPACE 2013 Conference and Exposi-tion (San Diego, 2013).

R. E. Bitten, M. R. Hayhurst, D. L. Emmons, et al., “Phase E Cost Analysis for NASA Science Missions,” AIAA 2012 SPACE Conference and Exposition (Pasadena, CA, 2012).

R. E. Bitten and E. M. Mahr, “Instrument Schedule Delays: Potential Impact on Mission Development Cost for Re-cent NASA Projects,” International Geoscience and Remote Sensing Symposium, pp. 5658−5661 (Munich, Germany, 2012).

R. E. Bitten, E. M. Mahr, et al., “Reducing Development Risks in NASA Science Missions—Developing Instru-ments First,” AIAA 2012 SPACE Conference and Exposi-tion (Pasadena, CA, 2012).

J. Blake, “SAMPEX and Relativistic Electron Microbursts,” 2012 American Geophysical Union Fall Meeting (San Francisco, 2012).

J. B. Blake et al., “A Nonstorm Time Enhancement of Relativ-istic Electrons in the Outer Radiation Belt,” Geophysical Research Letters, Vol. 41, No. 1, pp. 7−12 (2014).

J. B. Blake et al., “Nonstorm Time Dynamics of Electron Radiation Belts Observed by the Van Allen Probes,” Geophysical Research Letters, Vol. 41, No. 2, pp. 229−235 (2014).

BOOKMARKS Recent Publications, Papers, and Patents by the Technical Staff


J. B. Blake, P. A. Carranza, S. G. Claudepierre, J. H. Clem-mons, W. R. Crain, Y. Dotan, J. F. Fennell, F. H. Fuentes, R. M. Galvan, J. S. George, M. Lalic, A. Y. Lin, M. D. Looper, D. J. Mabry, J. E. Mazur, B. McCarthy, C. Q. Nguyen, T. P. O’Brien, M. A. Perez, M. T. Redding, J. L. Roeder, D. J. Salvaggio, G. A. Sorensen, S. Yi, M. P. Za-krewski, et al., “The Magnetic Electron Ion Spectrometer (MagEIS) Instruments aboard the Radiation Belt Storm Probes (RBSP) Spacecraft,” Space Science Reviews, Vol. 179, No. 1-4, pp. 383−421 (2013).

J. B. Blake, S. G. Claudepierre, J. H. Clemmons, J. F. Fen-nell, T. P. O’Brien, D. Salvaggio, et al., “Science Goals and Overview of the Radiation Belt Storm Probes (RBSP) En-ergetic Particle, Composition, and Thermal Plasma (ECT) Suite on NASA’s Van Allen Probes Mission,” Space Science Reviews, Vol. 179, No. 1-4, pp. 311−336 (2013).

J. B. Blake, J. Fennell, S. Claudepierre, et al., “Excitation of Poloidal Standing Alfvén Waves through Drift Resonance Wave-Particle Interaction,” Geophysical Research Letters, Vol. 40, No. 16, pp. 4127−4132 (2013).

J. B. Blake, J. F. Fennell, S. G. Claudepierre, et al., “An Unusu-al Enhancement of Low-Frequency Plasmaspheric Hiss in the Outer Plasmasphere Associated with Substorm-Injected Electrons,” Geophysical Research Letters, Vol. 40, No. 15, pp. 3798−3803 (2013).

J. B. Blake, J. F. Fennell, S. G. Claudepierre, et al., “Electron Acceleration in the Heart of the Van Allen Radiation Belts,” Science, Vol. 341, No. 6149, pp. 991−994 (2013).

J. B. Blake, J. F. Fennell, S. G. Claudepierre, et al., “Rapid Local Acceleration of Relativistic Radiation Belt Electrons by Magnetospheric Chorus,” Nature, Vol. 504, No. 7480, pp. 411−414 (2013).

J. B. Blake, M. D. Looper, J. E. Mazur, et al., “Measurements of Galactic Cosmic Ray Shielding with the CRaTER Instrument,” Space Weather, Vol. 11, No. 5, pp. 284−296 (2013).

J. B. Blake, J. Mazur, et al., “Contributions of Primary Par-ticles to Observed LET for the CRaTER Instrument on LRO,” 43rd International Conference on Environmental Systems (Vail, CO, 2013).

M. Boghosian, R. Herman, et al., “Magnetic Testing, and Modeling, Simulation and Analysis for Space Applica-tions,” 2013 IEEE International Symposium on Electromag-netic Compatibility, pp. 265−270 (Denver, 2013).

B. T. Bowes, L. G. Marcus, S. D. Gasster, and S. A. Reed, “Considerations of Quantum Key Distribution for Space Applications,” AIAA 2012 SPACE Conference and Exposi-tion (Pasadena, CA, 2012).

A. W. Bushmaker et al., “Electrical Transport and Channel Length Modulation in Semiconducting Carbon Nanotube

Field Effect Transistors,” IEEE Transactions on Nanotech-nology, Vol. 13, No. 2, pp. 176−181 (2014).

P. B. Cameron et al., “Proper Motions and Origins of AXP 1E 2259+586 and AXP 4U 0142+61,” Astrophysical Jour-nal, Vol. 772, No. 1, p. 11 (2013).

P. B. Cameron et al., “Proper Motions and Origins of SGR 1806-20 and SGR 1900+14,” Astrophysical Journal, Vol. 761, No. 1 (2012).

J. C. Camparo et al., “Long Term Behavior of Quartz Oscilla-tors in Space,” 44th Annual Precise Time and Time Interval Systems and Applications Meeting, pp. 335−349 (Reston, VA, 2012).

J. C. Camparo et al., “Long-Term Behavior of Rubidium Clocks in Space,” Proceedings of 2012 European Frequency and Time Forum, pp. 501−508 (Gothenburg, Sweden, 2012).

J. Camparo and G. Fathi, “The 2nd Harmonic Signal in Vapor-Cell Clocks & Error-Signal Quality: Does S2 Imply dS1/dΔ?,” 2013 Joint European Frequency and Time Forum & International Frequency Control Symposium, pp. 224−227 (Prague, Czech Republic, 2013).

J. Camparo, M. Huang, and T. Driskell, “The Influence of La-ser Polarization Noise on the Short-Term Stability of CPT Atomic Clocks,” 2013 Joint European Frequency and Time Forum & International Frequency Control Symposium, pp. 612−615 (Prague, Czech Republic, 2013).

J. C. Camparo, F. Wang, Y. Chan, and W. E. Lybarger, “Oscil-lator Model for rf-Discharge Lamps Used in Atomic Clocks: The rf-Discharge as a Complex Permeability Medium,” National Technical Information Service (2013).

M. Caponi et al., “Initial Results from the Ozone Mapper Profiler Suite on the Suomi National Polar-Orbiting Partnership,” International Geoscience and Remote Sensing Symposium, pp. 1088−1091 (Munich, Germany, 2012).

M. Caponi et al., “OMPS Early Orbit Dark and Bias Evalu-ation and Calibration,” International Geoscience and Remote Sensing Symposium, pp. 1092−1095 (Munich, Germany, 2012).

M. Caponi et al., “Performance and Calibration of the Nadir Suomi-NPP Ozone Mapping Profiler Suite from Early-Orbit Images,” IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 6, No. 3, pp. 1539−1551 (2013).

J. C. Cardema, K. W. Rausch, D. I. Moyer, F. J. De Luccia, et al., “Operational Calibration of VIIRS Reflective Solar Band Sensor Data Records,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

D. M. Cardoza, S. D. La Lumondiere, M. A. Tockstein, S. C. Witczak, Y. Sin, B. J. Foran, W. T. Lotshaw, and S. C. Moss,



“Single Event Transients Induced by Picosecond Pulsed X-Ray Absorption in III-V Heterojunction Transistors,” IEEE Transactions on Nuclear Science, Vol. 59, No. 6, pp. 2729−2738 (2012).

M. Chen, C. Lemon, T. Guild, M. Schulz, J. Roeder, A. Lui, A. Keesee, J. Goldstein, G. Le, and J. Rodriguez, “Numeri-cal Simulations of the Ring Current during Geomagnetic Storms,” 2012 American Geophysical Union Fall Meeting (San Francisco, 2012).

M. Chen, C. L. Lemon, T. B. Guild, J. L. Roeder, et al., “Com-parison of Self-Consistent Simulations with Observed Magnetic Field and Ion Plasma Parameters in the Ring Current during the 10 August 2000 Magnetic Storm,” Journal of Geophysical Research-Space Physics, Vol. 117 (2012).

S. G. Claudepierre et al., “A Long-Lived Relativistic Electron Storage Ring Embedded in Earth’s Outer Van Allen Belt,” Science, Vol. 340, No. 6129, pp. 186−190 (2013).

S. G. Claudepierre et al., “Kelvin-Helmholtz Instability of the Magnetospheric Boundary in a Three-Dimensional Global MHD Simulation during Northward IMF Condi-tions,” Journal of Geophysical Research-Space Physics, Vol. 118, No. 9, pp. 5478−5496 (2013).

S. G. Claudepierre et al., “Prompt Energization of Relativis-tic and Highly Relativistic Electrons during a Substorm Interval: Van Allen Probes Observations,” Geophysical Research Letters, Vol. 41, No. 1, pp. 20−25 (2014).

S. G. Claudepierre, J. F. Fennell, et al., “Discovery of the Action of a Geophysical Synchrotron in the Earth’s Van Allen Radiation Belts,” Nature Communications, Vol. 4 (2013).

S. G. Claudepierre, J. F. Fennell, J. B. Blake, J. L. Roeder, J. H. Clemmons, et al., “Van Allen Probes Observation of Localized Drift Resonance between Poloidal Mode Ultra-Low Frequency Waves and 60 keV Electrons,” Geophysical Research Letters, Vol. 40, No. 17, pp. 4491−4497 (2013).

J. Clemmons, J. Fennell, J. Blake, J. Roeder, S. Claudepierre, H. Spence, and C. Kletzing, “Electron Microburst Physics Using the Burst Support Mode on RBSP’s MagEIS Instru-ment,” 2012 American Geophysical Union Fall Meeting (San Francisco, 2012).

J. H. Clemmons, R. W. Walterscheid, A. B. Christensen, and R. L. Bishop, “Rapid, Highly Structured Meridional Winds and Their Modulation by Non Migrating Tides: Measurements from the Streak Mission,” Journal of Geophysical Research: Space Physics, Vol. 118, No. 2, pp. 866−877 (2013).

J. G. Coffer, M. Huang, and J. C. Camparo, “Self-Pulsing in Alkali rf-Discharge Lamps,” Proceedings of 2012 IEEE International Frequency Control Symposium, pp. 687−691 (Baltimore, 2012).

D. J. Coleman and K. T. Luey, “VUV Modification of Surfac-es to Induce Film Formation,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

K. B. Crawford, D. L. Kim, R. J. Rudy, R. W. Russell, et al., “Evolution from Protoplanetary to Debris Discs: the Transition Disc around HD 166191,” Monthly Notices of the Royal Astronomical Society, Vol. 438, No. 4, pp. 3299−3309 (2014).

M. Crofton, J. Young, et al., “Further Results from the U.S. Round-Robin Experiment on Plasma Expansion Speed,” 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition (Grapevine, TX, 2013).

M. W. Crofton, J. C. Nocerino, J. A. Young, et al., “NEXT Ion Engine Plume Deposition Rates: QCM Measurements,” 52nd AIAA Aerospace Sciences Meeting (National Harbor, MD, 2013).

M. W. Crofton and J. E. Pollard, “Thrust Augmentation by Charge Exchange,” 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference (San Jose, 2013).

M. W. Crofton, J. A. Young, et al., “A U.S. Round-Robin Experiment on Characteristics of Arc Plasma Expansion,” 4th AIAA Atmospheric and Space Environments Confer-ence (New Orleans, 2012).

M. W. Crofton, J. A. Young, et al., “First Preliminary Results from U.S. Round Robin Tests,” IEEE Transactions on Plasma Science, Vol. 41, No. 12, pp. 3310−3322 (2013).

E. Deionno, D. C. Marvin, and S. H. Liu, “Assessment of AP9 and Solar Cell Degradation Models with Flight Data,” 2013 IEEE 39th Photovoltaic Specialists Conference, pp. 3103−3107 (Tampa, 2013).

E. Deionno, M. D. Looper, J. V. Osborn, et al., “Displacement Damage in TiO₂ Memristor Devices,” IEEE Transactions on Nuclear Science, Vol. 60, No. 2, pp. 1379−1383 (2013).

E. Deionno, M. D. Looper, J. V. Osborn, et al., “Radiation Effects Studies on Thin Film TiO₂ Memristor Devices,” IEEE Aerospace Conference Proceedings (Big Sky, MT, 2013).

F. J. De Luccia et al., “Early On-Orbit Performance of the Visible Infrared Imaging Radiometer Suite Onboard the Suomi National Polar-Orbiting Partnership (S-NPP) Satellite,” IEEE Transactions on Geoscience and Remote Sensing, Vol. 52, No. 2, pp. 1142−1156 (2014).

F. De Luccia, D. Moyer, K. Rausch, E. Haas, et al., “Discovery and Characterization of On-Orbit Degradation of the Visible Infrared Imaging Radiometer Suite (VIIRS) Rotat-ing Telescope Assembly (RTA),” Proceedings of SPIE—The International Society for Optical Engineering (2012).

J. D. Desain, T. J. Curtiss, J. K. Fuller, et al., “Test of Hybrid Rocket Fuel Grains with Swirl Patterns Fabricated Using


Rapid Prototyping Technology,” 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference (San Jose, 2013).

K. D. Diamant, R. Spektor, E. J. Beiting, J. A. Young, and T. J. Curtiss, “The Effects of Background Pressure on Hall Thruster Operation,” 48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit (Atlanta, 2012).

J. T. Dickey et al., “Professor Bud Peterson on His 60th Birth-day,” International Journal of Heat and Mass Transfer, Vol. 58, No. 1-2, pp. 3−5 (2013).

S. V. Didziulis, “A Perspective on the Properties and Surface Reactivities of Carbides and Nitrides of Titanium and Vanadium,” Coordination Chemistry Reviews, Vol. 257, No. 1, pp. 93−109 (2013).

M. Di Prinzio, “Three Lambert Formulations with Finite, Computable Bounds,” Advances in the Astronautical Sci-ences, pp. 2519−2537 (2012).

F. Di Teodoro et al., “SBS-Managed High-Peak-Power Nanosecond-Pulse Fiber-Based Master Oscillator Power Amplifier,” Optics Letters, Vol. 38, No. 13, pp. 2162−2164 (2013).

A. Doran et al., “Launch Vehicle Tracking Enhancement through Global Positioning System Metric Tracking,” IEEE Aerospace Conference Proceedings (Big Sky, MT, 2013).

R. B. Dybdal, S. J. Curry, F. Lorenzelli, and D. J. Hinshil-wood, “Multiple Polarization Communications,” IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) (Chicago, 2012).

J. L. Emdee, “EELV Progress in Compliance with U.S. Space Debris Mitigation Policies,” AIAA SPACE 2012 Conference and Exposition (Pasadena, CA, 2012).

B. Etefia et al., “Supporting Military Communications with Named Data Networking: An Emulation Analysis,” Proceedings—IEEE Military Communications Conference (Orlando, FL, 2012).

J. Feeley and I. Csiszar, “Product Maturity Status for the SNPP Sensor and Environmental Data Records,” 93rd American Meteorological Society Annual Meeting (Austin, TX, 2013).

J. Fennell, J. Blake, J. Clemmons, H. Spence, S. Claudepierre, and J. Roeder, “Initial Look at the Electron Slot and Inner Zone Regions with RBSP/MagEIS,” 2012 American Geo-physical Union Fall Meeting (San Francisco, 2012).

J. Fennell, J. B. Blake, M. Looper, et al., “First Results from CSSWE CubeSat: Characteristics of Relativistic Electrons in the Near-Earth Environment during the October 2012 Magnetic Storms,” Journal of Geophysical Research-Space Physics, Vol. 118, No. 10, pp. 6489−6499 (2013).

R. Fields, “Rapid Low Cost Electro-Optic Prototyping for

Space through Use of Cubesats,” Applied Industrial Optics: Spectroscopy, Imaging, and Metrology (2012).

C. E. Foerster, V. Goyal, J. Rome, D. N. Patel, and G. L. Steck-el, “Strength of Composite Foam Core Sandwich Struc-tures Subjected to Thermomechanical Loading,” AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference (Boston, 2013).

E. Fong and T. T. Lam, “Application of Solution Structure Theorems for Asymmetric Heating in Thin Films,” 44th AIAA Thermophysics Conference (San Diego, 2013).

E. Fong and T. T. Lam, “Asymmetrical Collision of Thermal Waves in Thin Films: An Analytical Solution,” Interna-tional Journal of Thermal Sciences, Vol. 77, pp. 55−65 (2014).

B. Foran, M. Brodie, et al., “Material Evidence for Multiple Firings of Ancient Athenian Red-Figure Pottery,” Jour-nal of the American Ceramic Society, Vol. 96, No. 7, pp. 2031−2035 (2013).

J. Fortune and R. Valerdi, “A Framework for Reusing Systems Engineering Products,” Systems Engineering, Vol. 16, No. 3, pp. 304−312 (2013).

P. D. Fuqua, C. J. Panetta, J. D. Barrie, et al., “Out of Band Scatter Measurements from OLI Optical Bandpass Fil-ters,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

C. M. Gee, G. Sefler, P. T. S. Devore, and G. C. Valley, “Spu-rious-Free Dynamic Range of a High-Resolution Pho-tonic Time-Stretch Analog-to-Digital Converter System,” Microwave and Optical Technology Letters, Vol. 54, No. 11, pp. 2558−2563 (2012).

J. Geis, C. Florio, D. Moyer, K. Rausch, and F. De Luccia, “VIIRS Day-Night Band Gain and Offset Determination and Performance,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

L. Gelinas, J. Hecht, R. Walterscheid, I. Reid, and J. Woithe, “Sources and Ducting of Gravity Waves Observed at Adelaide and Alice Springs,” 2012 American Geophysical Union Fall Meeting (San Francisco, 2012).

L. J. Gelinas, R. L. Walterschied, et al., “Observations of an Inertial Peak in the Intrinsic Wind Spectrum Shifted by Rotation in the Antarctic Vortex,” Journal of the Atmo-spheric Sciences, Vol. 69, No. 12, pp. 3800−3811 (2012).

J. S. George, R. Koga, R. M. Moision, et al., “Single Event Burnout Observed in Schottky Diodes,” IEEE Radiation Effects Data Workshop (San Francisco, 2013).

E. Ghashghai and J. Hamilton, “Net-Centric Network and Operational Management,” AIAA SPACE Conference and Exposition (Pasadena, CA, 2012).

R. Gong, M. Broder, L. Jocic, and J. Gee, “Space Architecture



Transition with Hosted Payloads,” AIAA SPACE Confer-ence and Exposition (Pasadena, CA, 2012).

V. K. Goyal and J. I. Rome, “Analysis Methodology for Assessing Delaminations in Composite Overwrapped Pressure Vessels,” 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference (Honolulu, 2012).

V. K. Goyal, J. I. Rome, P. M. Schubel, D. N. Patel, and G. L. Steckel, “Predicting and Measuring the Strength Reduc-tion of Sandwich Structures with Spliced Foam Cores,” 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference (Honolulu, 2012).

T. P. Graves, P. Hanson, J. M. Michaelson, A. D. Farkas, and A. A. Hubble, “Fast Shutdown Protection System for Radio Frequency Breakdown and Multipactor Testing,” Review of Scientific Instruments, Vol. 85, No. 2 (2014).

S. Guarro, “On the Estimation of Space Launch Vehicle Reli-ability,” International Journal of Performability Engineer-ing, Vol. 9, No. 6, pp. 619−631 (2013).

S. Guarro, “Risk Assessment of New Space Launch and Supply Vehicles,” 11th International Probabilistic Safety Assessment and Management Conference and the An-nual European Safety and Reliability Conference, pp. 5157−5164 (2012).

T. Guild, P. O’Brien, and M. Looper, “Inner Radiation Belt Dynamics and Climatology,” 2012 American Geophysical Union Fall Meeting (San Francisco, 2012).

M. E. Harmon, J. Schuetz, et al., “The Microstructure of Collagen Type I Gel Cross-Linked with Gold Nanopar-ticles,” Colloids and Surfaces B: Biointerfaces, Vol. 101, pp. 118−125 (2013).

J. H. Hecht, P. R. Straus, et al., “An Empirical Determination of Proton Auroral Far Ultraviolet Emission Efficiencies Using a New Nonclimatological Proton Flux Extrapola-tion Method,” Journal of Geophysical Research—Space Physics, Vol. 117 (2012).

M. Hecht, J. Tamaki, and D. Lo, “Modeling of Failure Detec-tion and Recovery in SysML,” 2013 IEEE International Symposium on Software Reliability Engineering Workshops, pp. 85−95 (Pasadena, CA, 2013).

J. M. Helt, “High Vacuum Tribometry Tests of Fluid Lubri-cants on Bearing Steels,” ACS National Meeting Book of Abstracts (San Diego, 2012).

H. Helvajian et al., “Welding Characteristics of Foturan Glass Using Ultrashort Laser Pulses,” 31st International Congress on Applications of Lasers and Electro-Optics, pp. 775−783 (Anaheim, CA, 2012).

J. Hicks, “Fast, Blind, and Joint Maximum Likelihood Esti-mation of MPSK Signal Parameters,” IEEE International Conference on Communications, pp. 3476−3481 (Ottawa,

Canada, 2012).

A. C. Hoheb, “System Engineering Competencies for Space System Program Managers,” AIAA SPACE 2013 Confer-ence and Exposition (San Diego, 2013).

F. R. Hoots, “Satellite Catalog Renumbering: What Does That Mean and Should I Be Worried,” National Technical Information Service (2013).

D. Houston, D. Buettner, and M. Hecht, “Defectivity Profil-ing with Dynamic COQUALMO: An Explication and Product Quality Retrospective,” Journal of Software: Evo-lution and Process, Vol. 24, No. 7, pp. 803−814 (2012).

D. X. Houston and D. J. Buettner, “Modeling User Story Completion of an Agile Software Process,” ACM Interna-tional Conference Proceeding Series, pp. 88−97 (2013).

M. Huang, T. U. Driskell, and J. C. Camparo, “Coherent Population Trapping and Polarization Fluctuations: The Independent-Modulator Approximation for Coherent-Population-Trapping Line Shapes,” Physical Review A, Vol. 87, No. 5 (2013).

P. Ionov, “Spectral Response of Fiber-Coupled Fabry-Perot Etalons,” Journal of the Optical Society of America, Vol. 31, No. 3, pp. 505−509 (2014).

B. C. Jacquot et al., “Atomically Precise Surface Engineering of Silicon CCDs for Enhanced UV Quantum Efficiency,” Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films, Vol. 31, No. 1 (2013).

A. B. Jenkin, J. McVey, and B. D. Howard, “Uncertainty in Lifetime of Highly Eccentric Transfer Orbits Due to Solar Resonances,” Advances in the Astronautical Sciences, pp. 3041−3057 (2012).

A. B. Jenkin, J. P. McVey, and G. E. Peterson, “ISS Protection Process for the COLA Gap after Launch,” AIAA SPACE Conference and Exposition (2012).

A. B. Jenkin, M. E. Sorge, G. E. Peterson, J. P. McVey, and B. B. Yoo, “100-Year Low Earth Orbit Debris Popula-tion Model,” Advances in the Astronautical Sciences, pp. 139−157 (2012).

C. Jo-Chieh, C. Sunshine, et al., “Protected MILSATCOM Design for Affordability Risk Reduction (DFARR),” 2013 IEEE Military Communications Conference, pp. 998−1001 (San Diego, 2013).

A. M. Kabe and E. Perl, “Limitations of Base Shake Analysis and Testing of Flight Configured Spacecraft,” European Space Agency (2012).

R. Khullar et al., “Advanced Extremely High Frequency Mission Planning: Will Its Legacy Dictate Its Future?,” Proceedings—2012 IEEE 1st AESS European Conference on Satellite Telecommunications (Rome, 2012).

Y. Kim and H. Helvajian, “Local Modification of Speed of Sound in Lithium Alumino-Silicate Glass/Ceramic Mate-


rial by Pulsed Laser Irradiation and Thermal Process-ing,” Journal of Physical Chemistry, Vol. 117, No. 46, pp. 11954−11962 (2013).

K. W. Kloster et al., “Preliminary Analysis of Ballistic Trajec-tories to Uranus Using Gravity-Assists from Venus, Earth, Mars, Jupiter, and Saturn,” Advances in the Astronautical Sciences, pp. 3411−3428 (2012).

R. Koga et al., “The Single Event Revolution,” IEEE Transac-tions on Nuclear Science, Vol. 60, No. 3, pp. 1824−1835 (2013).

R. Koga, C. Paul, D. Romeo, V. Petrosyan, and J. George, “Single Event Effects Sensitivity of 180 and 350 nm SiGe HBT Microcircuits,” 2013 IEEE Radiation Effects Data Workshop (San Francisco, 2013).

R. Kohli et al., “Decision Gate Process for Assessment of a NASA Technology Development Portfolio,” AIAA SPACE Conference and Exposition (Pasadena, CA, 2012).

S. Kohn et al., “Commentary: JWST Near-Infrared Detector Degradation—Finding the Problem, Fixing the Problem, and Moving Forward,” AIP Advances, Vol. 2, No. 2 (2012).

T. Kopp et al., “First-Light Imagery from Suomi NPP VIIRS,” Bulletin of the American Meteorological Society, Vol. 94, No. 7, pp. 1019−1029 (2013).

J. Kreng et al., “EELV Incorporates GPS Metric Tracking as a Range Tracking Source,” Proceedings of the International Telemetering Conference (San Diego, 2012).

D. Kunkee et al., “Foreword to the Special Issue on Radio Frequency Interference: Identification, Mitigation, and Impact Assessment,” IEEE Transactions on Geoscience and Remote Sensing, Vol. 51, No. 10, pp. 4915−4917 (2013).

S. D. La Lumondiere, Y. Sin, W. T. Lotshaw, S. C. Moss, et al., “Characteristics of Bulk InGaAsSbN/GaAs Grown by Metalorganic Vapor Phase Epitaxy (MOVPE),” Journal of Crystal Growth, Vol. 370, pp. 163−167 (2013).

T. T. Lam, “A Generalized Heat Conduction Solution for Ultrafast Laser Heating in Metallic Films,” International Journal of Heat and Mass Transfer, Vol. 73, pp. 330−339 (2014).

T. T. Lam, “A Unified Solution of Several Heat Conduction Models,” International Journal of Heat and Mass Transfer, Vol. 56, No. 1-2, pp. 653−666 (2013).

T. T. Lam and E. Fong, “Application of Solution Structure Theorems to Cattaneo-Vernotte Heat Conduction Equa-tion with Non-Homogeneous Boundary Conditions,” Heat and Mass Transfer, Vol. 49, No. 4, pp. 509−519 (2013).

J. R. Lince, A. M. Pluntze, S. A. Jackson, G. Radhakrishnan, and P. M. Adams, “Tribochemistry of MoS₃ Nanoparticle Coatings,” Tribology Letters, Vol. 53, No. 3, pp. 543−554 (2014).

D. Liu, S. V. Didziulis, and J. D. Fowler, “Assessment of Particle Deposition Inside Payload Fairing from Launch Vehicle Plume Contribution,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

M. D. Looper et al., “LEEM: A New Empirical Model of Radiation-Belt Electrons in the Low-Earth-Orbit Region,” Journal of Geophysical Research—Space Physics, Vol. 117 (2012).

M. D. Looper et al., “Relative Contributions of Galactic Cos-mic Rays and Lunar Proton ‘Albedo’ to Dose and Dose Rates near the Moon,” Space Weather—The International Journal of Research and Applications, Vol. 11, No. 11, pp. 643−650 (2013).

M. D. Looper, J. E. Mazur, et al., “Energy Spectra, Composi-tion, and Other Properties of Ground-Level Events dur-ing Solar Cycle 23,” Space Science Reviews, Vol. 171, No. 1-4, pp. 97−120 (2012).

M. D. Looper, J. E. Mazur, J. B. Blake, et al., “The Deep Space Galactic Cosmic Ray Lineal Energy Spectrum at Solar Minimum,” Space Weather, Vol. 11, No. 6, pp. 361−368 (2013).

M. D. Looper, J. E. Mazur, J. B. Blake, et al., “The Radiation Environment near the Lunar Surface: CRaTER Observa-tions and Geant4 Simulations,” Space Weather, Vol. 11, No. 4, pp. 142−152 (2013).

W. T. Lotshaw, S. D. La Lumondiere, et al., “Investigation of Carrier Removal from QD TJSCs,” Proceedings of SPIE—The International Society for Optical Engineering (2013).

E. C. Lundgren et al., “Design and Maintainability Consider-ations regarding the Effects of Suborbital Flights on Com-posite Constructed Vehicles,” 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference (Honolulu, 2012).

D. K. Lynch, R. J. Rudy, R. W. Russell, et al., “The Expanding Dusty Bipolar Nebula around the Nova V1280 Scorpi,” Astronomy and Astrophysics, Vol. 545 (2012).

S. Maghsoudy-Louyeh et al., “Subsurface Image Analysis of Plant Cell Wall with Atomic Force Microscopy,” Journal of Advanced Microscopy Research, Vol. 8, No. 2, pp. 100−104 (2013).

V. N. Mahajan, “Aberration Balancing, Orthonormal Polyno-mials, and Wavefront Analysis,” Frontiers in Optics (2012).

V. N. Mahajan, “Study of Zernike Polynomials of an Ellipti-cal Aperture Obscured with an Elliptical Obscuration: Comment,” Applied Optics, Vol. 52, No. 24, pp. 5962−5964 (2013).

V. N. Mahajan et al., “Imaging by a System with a Hexago-nal Pupil,” Applied Optics, Vol. 52, No. 21, pp. 5112−5122 (2013).

V. N. Mahajan et al., “Imaging Characteristics of Zernike and



Annular Polynomial Aberrations,” Applied Optics, Vol. 52, No. 10, pp. 2062−2074 (2013).

V. N. Mahajan et al., “Orthonormal Aberration Polynomials for Optical Systems with Circular and Annular Sector Pu-pils,” Applied Optics, Vol. 52, No. 6, pp. 1136−1147 (2013).

E. M. Mahr and R. E. Bitten, “Evaluating Options for En-hancing Technology Development and Controlling Cost Growth,” International Geoscience and Remote Sensing Symposium, pp. 5654−5657 (Munich, Germany, 2012).

N. Marechal, R. Dickinson, and G. Karmyan, “A 2D Wave-number Domain Phase Model for Ground Moving Vehicles in Synthetic Aperture Radar Imagery,” Inverse Problems, Vol. 29, No. 5 (2013).

N. J. Marechal, S. S. Osofsky, and R. M. Bloom, “Demon-stration of W-Band SAR Imagery with a Ground-Based System Having 7.5 GHz of Bandwidth Obtained with a Stepped Chirp Waveform,” IEEE Transactions on Aerospace and Electronic Systems, Vol. 49, No. 4, pp. 2522−2532 (2013).

S. K. Martinelli, J. P. Penn, D. Judnick, O. Rossi, C. Ran-ieri, and A. Feistel, “Electric Propulsion Tug Modeling Improvements and Application to the NASA/DARPA Manned Geosynchronous Servicing Study,” AIAA SPACE Conference and Exposition (Pasadena, CA, 2012).

A. Matache and E. L. Valles, “Performance of Decoder-Based Algorithms for Signal Synchronization for DSSS Wave-forms,” IEEE Aerospace Conference Proceedings (Big Sky, MT, 2013).

J. Mazur et al., “A Small Spacecraft Mission with Large Ac-complishments,” Eos, Transactions American Geophysical Union, Vol. 93, No. 34, pp. 325−326 (2012).

J. Mazur et al., “Dose Spectra from Energetic Particles and Neutrons,” Space Weather—The International Journal of Research and Applications, Vol. 11, No. 10, pp. 547−556 (2013).

J. Mazur et al., “Modeling Solar Proton Access to Geostation-ary Spacecraft with Geomagnetic Cutoffs,” Advances in Space Research, Vol. 52, No. 11, pp. 1939−1948 (2013).

J. Mazur et al., “Validation of PREDICCS Using LRO/CRa-TER Observations during Three Major Solar Events in 2012,” Space Weather, Vol. 11, No. 6, pp. 350−360 (2013).

J. Mazur, L. Friesen, A. Lin, D. Mabry, N. Katz, Y. Dotan, J. George, J. B. Blake, M. Looper, M. Redding, T. P. O’Brien, J. Cha, A. Birkitt, P. Carranza, M. Lalic, F. Fuentes, R. Gal-van, and M. McNab, “The Relativistic Proton Spectrom-eter (RPS) for the Radiation Belt Storm Probes Mission,” Space Science Reviews, Vol. 179, No. 1-4, pp. 221−261 (2013).

J. F. McNeill, E. L. Chapman, and M. E. Sklar, “Under-

standing Cost Growth during Operations of Planetary Missions: An Explanation of Changes,” IEEE Aerospace Conference Proceedings (Big Sky, MT, 2013).

J. P. McVey and C. Chao, “Automated Ballistic Coefficient Estimation Technique to Analyze the Debris from the Cosmos-2251 and Iridium-33 Collision,” Advances in the Astronautical Sciences, pp. 173−185 (2012).

J. P. McVey and N. Melamed, “Survey of Potentially Hazard-ous Object Threat Negation Campaign Options,” Acta Astronautica, Vol. 90, No. 1, pp. 22−32 (2013).

M. Mecklenburg et al., “Dark-Field Transmission Electron Microscopy and the Debye-Waller Factor of Graphene,” Physical Review B, Vol. 87, No. 4 (2013).

M. Mecklenburg et al., “Transparent and Flexible Graphene Charge-Trap Memory,” ACS Nano, Vol. 6, No. 9, pp. 7879−7884 (2012).

N. Melamed, “Development of a Handbook and an Online Tool on Defending Earth against Potentially Hazardous Objects,” Acta Astronautica, Vol. 90, No. 1, pp. 165−172 (2013).

A. W. Merrill, M. A. Clark, J. Hoffman, G. L. Gallien, and T. M. Walsh, “Commerce Spectrum Management Advisory Committee (CSMAC) Working Group (WG) 3 Phase 2 Study Summary,” National Technical Information Service (2013).

A. K. Mollner et al., “Validation of Satellite Sounder Envi-ronmental Data Records: Application to the Cross-Track Infrared Microwave Sounder Suite,” Journal of Geo-physical Research—Atmospheres, Vol. 118, No. 24, pp. 13628−13643 (2013).

D. Moyer et al., “Analysis of Suomi-NPP VIIRS Vignetting Functions Based on Yaw Maneuver Data,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

D. Moyer et al., “Preliminary Assessment of Suomi-NPP VIIRS On-Orbit Radiometric Performance,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

D. Moyer, F. De Luccia, et al., “VIIRS Thermal Emissive Bands Calibration Algorithm and On-Orbit Perfor-mance,” Proceedings of SPIE - The International Society for Optical Engineering (2012).

D. Moyer, F. De Luccia, et al., “VIIRS Thermal Emissive Bands On-Orbit Calibration Coefficient Performance Using Vicarious Calibration Results,” Proceedings of SPIE —The International Society for Optical Engineering (2013).

D. Moyer, E. Haas, F. De Luccia, K. Rausch, et al., “NPP VI-IRS Early On-Orbit Solar Diffuser Degradation Results,” International Geoscience and Remote Sensing Symposium,


pp. 1030−1033 (Munich, Germany, 2012).

T. Mulligan et al., “Composition Structure of Interplanetary Coronal Mass Ejections from Multispacecraft Obser-vations, Modeling, and Comparison with Numerical Simulations,” Astrophysical Journal, Vol. 761, No. 2, p. 175 (2012).

T. Mulligan et al., “Heliospheric Imaging of 3D Density Structures during the Multiple Coronal Mass Ejections of Late July to Early August 2010,” Solar Physics, Vol. 285, No. 1-2, pp. 317−348 (2013).

T. Mulligan et al., “Multi-Point Shock and Flux Rope Analy-sis of Multiple Interplanetary Coronal Mass Ejections around 2010 August 1 in the Inner Heliosphere,” Astro-physical Journal, Vol. 758, No. 1, p. 18 (2012).

T. Mulligan, J. B. Blake, et al., “Diffusion Coefficients, Short-Term Cosmic Ray Modulation, and Convected Magnetic Structures,” Advances in Astronomy (2013).

T. Mulligan, A. A. Reinard, and B. J. Lynch, “Advancing In Situ Modeling of ICMEs: New Techniques for New Ob-servations,” Journal of Geophysical Research: Space Physics, Vol. 118, No. 4, pp. 1410−1427 (2013).

J. J. Murphy, “Simulation of a Stationary Plasma Thruster Using the Space-Time Conservation Method,” 21st AIAA Computational Fluid Dynamics Conference (San Diego, 2013).

E. J. Nemanick, “Electrochemistry of Lithium-Oxygen Bat-teries Using Microelectrode Voltammetry,” Journal of Power Sources, Vol. 247, pp. 26−31 (2014).

E. J. Nemanick and R. P. Hickey, “The Effects of O₂ Pres-sure on Li-O₂ Secondary Battery Discharge Capacity and Rate Capability,” Journal of Power Sources, Vol. 252, pp. 248−251 (2014).

D. Nigg and J. Evans, “Developing Rapid Tradespace Exploration Trends through Multidisciplinary Design Optimization,” AIAA SPACE Conference and Exposition (Pasadena, CA, 2012).

T. P. O’Brien, “Breaking All the Invariants: Anomalous Elec-tron Radiation Belt Diffusion by Pitch Angle Scattering in the Presence of Split Magnetic Drift Shells,” Geophysical Research Letters, Vol. 41, No. 2, pp. 216−222 (2014).

T. P. O’Brien et al., “Focusing on Size and Energy Depen-dence of Electron Microbursts from the Van Allen Radia-tion Belts,” Space Weather—The International Journal of Research and Applications, Vol. 10 (2012).

T. P. O’Brien et al., “Near-Earth Space Radiation Models,” IEEE Transactions on Nuclear Science, Vol. 60, No. 3, pp. 1691−1705 (2013).

T. P. O’Brien et al., “Transitioning Research to Operations:

Transforming the ‘Valley of Death’ into a ‘Valley of Op-portunity,’ " Space Weather—The International Journal of Research and Applications, Vol. 11, No. 11, pp. 637−640 (2013).

T. P. O’Brien, S. G. Claudepierre, J. B. Blake, J. F. Fennell, J. H. Clemmons, J. R. Roeder, et al., “An Empirically Observed Pitch-Angle Diffusion Eigenmode in the Earth’s Electron Belt Near L* = 5.0,” Geophysical Research Letters, Vol. 41, No. 2, pp. 251−258 (2014).

T. P. O’Brien and A. Crew, “A Review of Electron Micro-bursts,” 2012 American Geophysical Union Fall Meeting (San Francisco, 2012).

T. P. O’Brien, T. B. Guild, et al., “AE9, AP9 and SPM: New Models for Specifying the Trapped Energetic Particle and Space Plasma Environment,” Space Science Reviews, Vol. 179, No. 1-4, pp. 579−615 (2013).

R. P. Patera, “Attitude Propagation for a Slewing Angular Rate Vector with Time Varying Slew Rate,” Advances in the Astronautical Sciences, pp. 2529−2546 (2012).

E. Perl, A. J. Peterson, et al., “Another Look at the Draft MIL-STD-1540E Unit Random Vibration Test Requirements,” European Space Agency (2012).

J. D. Perreault, “Triple Wollaston-Prism Complete-Stokes Imaging Polarimeter,” Optics Letters, Vol. 38, No. 19, pp. 3874−3877 (2013).

G. E. Peterson, “Effect of Future Space Debris on Mission Utility and Launch Accessibility,” Advances in the Astro-nautical Sciences, pp. 201−215 (2012).

R. G. Pettit and N. Mezcciani, “Highlighting the Challenges of Model-Based Engineering for Spaceflight Software Systems,” ICSE Workshop on Software Engineering for Adaptive and Self-Managing Systems, pp. 51−54 (San Francisco, 2013).

A. L. Polite-Wilson, “Ensuring Competency Optimization from a Systems Thinking Perspective,” AIAA SPACE 2013 Conference and Exposition (San Diego, 2013).

G. Radhakrishnan, P. M. Adams, B. Foran, M. V. Quinzio, and M. J. Brodie, “Pulsed Laser Deposited Si on Multi-layer Graphene as Anode Material for Lithium Ion Batter-ies,” APL Materials, Vol. 1, No. 6 (2013).

C. L. Ranieri et al., “Hypersonic, Aerodynamically Con-trolled, Path Constrained Reentry Optimization Using Pseudospectral Methods,” Advances in the Astronautical Sciences, pp. 713−732 (2012).

K. Rausch et al., “Impacts of VIIRS SDR Performance on Ocean Color Products,” Journal of Geophysical Research—Atmospheres, Vol. 118, No. 18, pp. 10347−10360 (2013).

K. Rausch, F. De Luccia, D. Moyer, J. Cardema, et al.,



“SUOMI NPP VIIRS Reflective Solar Band Radiometric Calibration,” International Geoscience and Remote Sensing Symposium, pp. 1050−1052 (2012).

K. Rausch, S. Houchin, J. Cardema, G. Moy, E. Haas, and F. J. De Luccia, “Automated Calibration of the Suomi National Polar Orbiting Partnership (S-NPP) Visible Infrared Im-aging Radiometer Suite (VIIRS) Reflective Solar Bands,” Journal of Geophysical Research—Atmospheres, Vol. 118, No. 24, pp. 13434−13442 (2013).

S. A. Reed et al., “High-Intensity Laser-Driven Proton Ac-celeration Enhancement from Hydrogen Containing Ultrathin Targets,” Applied Physics Letters, Vol. 103, No. 14 (2013).

D. F. Rock, “Using Differential Ray Tracing in Stray Light Analysis,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

J. I. Rome, V. K. Goyal, et al., “Specimen Size and Effective Compressive Stiffness of 3d Fiber Reinforced Foam Core Sandwich Structures,” 28th Annual Technical Conference of the American Society for Composites, pp. 1325−1334 (State College, PA, 2013).

J. I. Rome, V. K. Goyal, P. Schubel, G. Steckel, D. Patel, Y. Kim, et al., “Modeling Failure of 3D Fiber Reinforced Foam Core Sandwich Structures with Defects,” 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dy-namics and Materials Conference (Honolulu, 2012).

J. I. Rome, V. K. Goyal, P. M. Schubel, D. N. Patel, and G. L. Steckel, “Identification of Failure Mechanisms in Sand-wich Structures with Foam Core Thickness Mismatches,” 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference (Honolulu, 2012).

G. Rosene et al., “A Model to Estimate Separator Forces during Ball Speed Variations,” ASTM Special Technical Publication, pp. 71−91 (2012).

R. Russell et al., “Spiral Arms in the Asymmetrically Illumi-nated Disk of MWC 758 and Constraints on Giant Plan-ets,” Astrophysical Journal, Vol. 762, No. 1, p. 13 (2013).

R. W. Russell et al., “High-Resolution Near-Infrared Po-larimetry of a Circumstellar Disk Around UX Tau A,” Publications of the Astronomical Society of Japan, Vol. 64, No. 6 (2012).

R. W. Russell et al., “Imaging the Disk and Jet of the Classical T Tauri Star AA Tau,” Astrophysical Journal, Vol. 762, No. 1, p. 7 (2013).

R. W. Russell et al., “Resolving the Gap and AU-Scale Asym-metries in the Pre-Transitional Disk of V1247 Orionis,” Astrophysical Journal, Vol. 768, No. 1, p. 15 (2013).

R. W. Russell, D. K. Lynch, et al., “Relating Jet Structure to Photometric Variability: The Herbig Ae Star HD 163296,” Astronomy and Astrophysics, Vol. 563 (2014).

R. W. Russell, R. J. Rudy, D. J. Gutierrez, D. L. Kim, K. Craw-ford, et al., “Further Analysis of Infrared Spectrophoto-metric Observations of High Area to Mass Ratio (HAMR) Objects in GEO,” Acta Astronautica, Vol. 80, pp. 154−165 (2012).

P. M. Schubel et al., “Response and Damage Tolerance of Composite Sandwich Structures under Low Velocity Im-pact,” Proceedings of the Society for Experimental Mechan-ics, Vol. 52, No. 1, pp. 37−47 (2012).

A. D. Schutte et al., “A Unified Approach to the Modeling and Control of Multiscale Dynamical Systems,” Earth and Space 2012—Proceedings of the 13th ASCE Aerospace Di-vision Conference and the 5th NASA/ASCE Workshop on Granular Materials in Space Exploration, pp. 1361−1370 (Pasadena, CA, 2012).

G. A. Sefler and G. C. Valley, “Mitigation of Group-Delay-Ripple Distortions for Use of Chirped Fiber-Bragg Grat-ings in Photonic Time-Stretch ADCs,” Journal of Light-wave Technology, Vol. 31, No. 7, pp. 1093−1100 (2013).

S. S. Shen and K. A. Roettiger, “Detection of Abandoned Mines/Caves Using Airborne LWIR Hyperspectral Data,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

Y. Sin, B. Foran, N. Presser, S. La Lumondiere, W. Lotshaw, and S. C. Moss, “Traps and Defects in Pre- and Post-Proton Irradiated AlGaN-GaN High Electron Mobility Transistors and AlGaN Schottky Diodes,” Proceedings of SPIE—The International Society for Optical Engineering (2013).

Y. Sin, N. Presser, S. La Lumondiere, N. Ives, W. Lotshaw, and S. C. Moss, “Catastrophic Optical Bulk Damage (COBD): A New Degradation Mode in High Power InGaAs-AlGaAs Strained QW Lasers,” Conference Di-gest—IEEE International Semiconductor Laser Conference, pp. 116−117 (San Diego, 2012).

Y. Sin, S. La Lumondiere, B. Foran, N. Ives, N. Presser, W. Lotshaw, and S. C. Moss, “Catastrophic Degradation in High Power InGaAs-AlGaAs Strained Quantum Well Lasers and InAs-GaAs Quantum Dot Lasers,” Proceedings of SPIE—The International Society for Optical Engineering (2013).

Y. Sin, S. La Lumondiere, B. Foran, W. Lotshaw, and S. C. Moss, “Catastrophic Optical Bulk Damage (COBD) Processes in Aged and Proton-Irradiated High Power InGaAs-AlGaAs Strained Quantum Well Lasers,” Pro-ceedings of SPIE—The International Society for Optical Engineering (2013).

Y. Sin, S. La Lumondiere, B. Foran, W. Lotshaw, S. C. Moss, et al., “Carrier Dynamics and Defects in Bulk 1eV In-GaAsNSb Materials and InGaAs Layers with MBL Grown by MOVPE for Multi-Junction Solar Cells,” Materials


Research Society Symposium Proceedings, pp. 245−251 (San Francisco, 2013).

Y. Sin, S. La Lumondiere, W. Lotshaw, S. C. Moss, et al., “Carrier Dynamics in Bulk 1eV InGaAsNSb Materials and Epitaxial Lift Off GaAs-InAlGaP Layers Grown by MOVPE for Multi-Junction Solar Cells,” Proceedings of SPIE—The International Society for Optical Engineering (2013).

K. Siri, “Group Maximum Power Tracking for Distributed Power Sources,” 11th International Energy Conversion Engineering Conference (San Jose, 2013).

P. Smith, M. Ferringer, R. Kelly, and I. Min, “Budget-Con-strained Portfolio Trades Using Multiobjective Optimiza-tion,” Systems Engineering, Vol. 15, No. 4, pp. 461−470 (2012).

M. E. Sorge et al., “Rapid Orbital Characterization of Local Area Space Objects Utilizing Image-Differencing Tech-niques,” Proceedings of SPIE—The International Society for Optical Engineering (2013).

M. E. Sorge et al., “Sensor Model for Space-Based Local Area Sensing of Debris,” Proceedings of SPIE—The International Society for Optical Engineering (2013).

J. R. Srour and J. W. Palko, “Displacement Damage Effects in Irradiated Semiconductor Devices,” IEEE Transactions on Nuclear Science, Vol. 60, No. 3, pp. 1740−1766 (2013).

D. W. Stephens and P. Broussinos, “Rideshare on EELV Us-ing ESPA—Challenges and Opportunities,” AIAA SPACE Conference and Exposition (Pasadena, CA, 2012).

A. G. Sun, M. W. Crofton, J. A. Young, W. A. Cox, and E. J. Beiting, “L-, S-, and C-Band EMI Measurement and Characterization of Spacecraft ESD Events,” IEEE Trans-actions on Plasma Science, Vol. 41, No. 12, pp. 3505−3511 (2013).

Y. R. Takeuchi, S. E. Davis, and M. A. Eby, “Steel and Hybrid Spacecraft Ball-Bearing Thermal Conductance Compari-sons,” ASTM Special Technical Publication, pp. 118−142 (2012).

Y. R. Takeuchi, S. E. Davis, M. A. Eby, J. K. Fuller, D. L. Taylor, and M. J. Rosado, “Bearing Thermal Conductance Measurement Test Method and Experimental Design,” ASTM Special Technical Publication, pp. 92−117 (2012).

D. P. Taylor, W. W. Hansen, L. Steffeney, and C. Chu, “Mi-cromachined Reference Samples for Particle Counting,” Proceedings of SPIE—The International Society for Optical Engineering (2012).

F. D. Teodoro, “High-Power Fiber Laser Sources for Remote Sensing,” Proceedings of SPIE—The International Society for Optical Engineering (2013).

J. Thordahl et al., “Study of Unsteady Surface Pressure on a

Turret via Pressure-Sensitive Paint,” 44th AIAA Plasmady-namics and Lasers Conference (San Diego, 2013).

J. Thordahl et al., “The Comparison of Unsteady Pressure Field over Flat- and Conformal-Window Turrets Using Pressure Sensitive Paint,” 44th AIAA Plasmadynamics and Lasers Conference (San Diego, 2013).

J. Thordahl et al., “The Estimation of the Unsteady Aerody-namic Force Applied to a Turret in Flight,” 44th AIAA Plasmadynamics and Lasers Conference (San Diego, 2013).

M. M. Tong, “Inverse Mass Matrix Factorization Using Mo-mentum Equations of a Rigid Multibody System,” AIAA Guidance, Navigation, and Control Conference (Minne-apolis, 2012).

D. Tratt, K. Buckland, S. Young, D. Riley, and I. Leifer, “Source Attribution of Methane Emission from Petro-leum Production Operations Using High-Resolution Airborne Thermal-Infrared Imaging Spectrometry,” 2012 American Geophysical Union Fall Meeting (San Francisco, 2012).

D. M. Tratt, “Remote Sensing Atmospheric Trace Gases with Infrared Imaging Spectroscopy,” Eos, Transactions Ameri-can Geophysical Union, Vol. 93, No. 50, p. 525 (2012).

D. M. Tratt, K. N. Buckland, S. J. Young, P. D. Johnson, et al., “Remote Sensing Visualization and Quantification of Ammonia Emission from an Inland Seabird Colony,” Journal of Applied Remote Sensing, Vol. 7, No. 1 (2013).

C. Tschan et al., “Advancing Intelligent Systems in the Aero-space Domain,” AIAA Infotech at Aerospace Conference (Boston, 2013).

C. Tschan et al., “Creating a Comprehensive Feature Space Library for Machine Learning,” AIAA Infotech at Aero-space Conference and Exhibit (Garden Grove, CA, 2012).

C. Tschan et al., “How Intelligent Is Your Satellite or Ground System?,” AIAA SPACE 2013 Conference and Exposition (San Diego, 2013).

G. C. Valley, G. A. Sefler, and T. J. Shaw, “Compressive Sens-ing of Sparse Radio Frequency Signals Using Optical Mixing,” Optics Letters, Vol. 37, No. 22, pp. 4675−4677 (2012).

G. C. Valley, G. A. Sefler, and T. J. Shaw, “Sensing RF Signals with the Optical Wideband Converter,” Proceedings of SPIE—The International Society for Optical Engineering (2013).

A. Vore et al., “High Lift Flap System for a Tailless Transport Aircraft,” 51st AIAA Aerospace Sciences Meeting Includ-ing the New Horizons Forum and Aerospace Exposition (Grapevine, TX, 2013).

D. Walker, L. De-Ling, and S. H. Liu, “Increasing the Limiting Efficiency of Space Solar Cells at End-of-Life,”



2013 IEEE 39th Photovoltaic Specialists Conference, pp. 2812−2815 (Tampa, 2013).

R. L. Walterscheid, “The Propagation of Transient Wave Packets in Highly Dissipative Media,” Journal of Geophysi-cal Research—Space Physics, Vol. 118, No. 2, pp. 878−884 (2013).

R. Walterscheid et al., “Angular Momentum Budget in Gen-eral Circulation Models of Superrotating Atmospheres: A Critical Diagnostic,” Journal of Geophysical Research—Planets, Vol. 117 (2012).

R. L. Walterscheid et al., “Wave Heating and Jeans Escape in the Martian Upper Atmosphere,” Journal of Geophysi-cal Research—Planets, Vol. 118, No. 11, pp. 2413−2422 (2013).

R. L. Walterscheid, L. J. Gelinas, J. H. Hecht, et al., “Instabili-ty Structures during Periods of Large Richardson Number (Ri>1/4): Evidence of Parametric Instability,” Journal of Geophysical Research—Atmospheres, Vol. 118, No. 13, pp. 6929−6939 (2013).

R. L. Walterscheid, J. H. Hecht, L. J. Gelinas, et al., “An In-tense Traveling Airglow Front in the Upper Mesosphere-Lower Thermosphere with Characteristics of a Bore Observed over Alice Springs, Australia, during a Strong 2 Day Wave Episode,” Journal of Geophysical Research D: Atmospheres, Vol. 117, No. 22 (2012).

M. A. Weaver and W. H. Ailor, “Reentry Breakup Recorder: Concept, Testing, Moving Forward,” AIAA SPACE Con-ference and Exposition (Pasadena, CA, 2012).

B. H. Weiller et al., “Graphene MEMS: AFM Probe Per-formance Improvement,” ACS Nano, Vol. 7, No. 5, pp. 4164−4170 (2013).

B. H. Weiller et al., “Vertical Graphene-Based Hot-Electron Transistor,” Nano Letters, Vol. 13, No. 6, pp. 2370−2375 (2013).

J. W. Welch, “Considerations in Assessing Risk for Tailoring Spacecraft Unit Thermal Test Cycle Requirements,” 42nd International Conference on Environmental Systems (San Diego, 2012).

N. P. Wells, S. D. La Lumondiere, Y. Sin, W. T. Lotshaw, S. C. Moss, et al., “Impact of Thermal Annealing on Bulk In-GaAsSbN Materials Grown by Metalorganic Vapor Phase Epitaxy,” Applied Physics Letters, Vol. 104, No. 5 (2014).

M. J. Wenkel et al., “FORMOSAT-7/COSMIC-2 GNSS Radio Occultation Constellation Mission for Global Weather Monitoring,” IEEE Aerospace Conference Proceedings (Big Sky, MT, 2013).

L. A. Wickman, “Comparing Crew Operations in Extreme Environments: Arctic Shipping vs. Outer Space,” Interna-tional Conference and Exhibition on Performance of Ships

and Structures in Ice, pp. 339−344 (Banff, Canada, 2012).

B. Y. Williams et al., “The Effect of Systematic Error in Forced Oscillation Testing,” 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition (Nashville, 2012).

D. B. Witkin, “Influence of Microstructure on Mechanical Behavior of Bi-Containing Pb-Free Solders,” IPC APEX EXPO Conference and Exhibition, pp. 540−560 (San Diego, 2013).

D. B. Witkin and I. A. Palusinski, “Influence of Low-Earth Orbit Exposure on the Mechanical Properties of Silicon Carbide,” Proceedings of SPIE—The International Society for Optical Engineering (2013).

D. R. Wood, “Analysis of Technology Transfer within Satel-lite Programs in Developing Countries Using Systems Architecture,” AIAA SPACE 2013 Conference and Exposi-tion (San Diego, 2013).

S. Yi, J. L. Hall, and B. P. Kasper, “Analysis, Testing, and Operation of the MAGI Thermal Control System,” AIP Conference Proceedings, pp. 1291−1298 (2014).

J. Yoshida, M. Cowdin, T. Mize, R. Kellogg, and D. Bearden, “Complexity Analysis of the Cost Effectiveness of PI-Led NASA Science Missions,” IEEE Aerospace Conference Proceedings (2013).

J. A. Young, M. W. Crofton, et al., “Annular Engine Develop-ment Status,” 49th AIAA/ASME/SAE/ASEE Joint Propul-sion Conference (San Jose, 2013).

J. A. Young, M. W. Crofton, et al., “Expanded Throttling Ca-pabilities of the NEXT Thruster,” 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference (San Jose, 2013).

J. A. Young, M. W. Crofton, W. Cox, D. C. Ferguson, R. C. Hoffmann, A. T. Wheelock, et al., “Measurement of ESD Plasma Propagation on a Positively Charged ISS Solar Array Coupon,” 2013 Abstracts IEEE International Confer-ence on Plasma Science (San Francisco, 2013).

J. A. Young, M. W. Crofton, W. A. Cox, and J. S. Tran, “Measurement of ESD Plasma Propagation on a Positively Charged Ring Coupon,” Digest of Technical Papers—IEEE International Pulsed Power Conference (San Francisco, 2013).

J. A. Young, M. W. Crofton, K. D. Diamant, et al., “Plume Characterization of the NEXT Thruster under Extended Throttle Conditions,” 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference (San Jose, 2013).

R. J. Zaldivar, J. P. Nokes, and H. I. Kim, “The Effect of Surface Treatment on Graphite Nanoplatelets Used in Fiber Reinforced Composites,” Journal of Applied Polymer Science, Vol. 131, No. 6 (2014).


Patents _________________________________N. W. Schulenburg, D. W. Warren, D. J. Rudy, M. G. Martino,

M. A. Chatelain, and M. A. Rocha, “Nadir Emissive Hyper-spectral Measurement Operation (NEHMO),” U.S. Patent No. 8,304,730, November 2012

A sensor system has been developed that enables high spectral and spatial resolution emissive hyperspectral imag-ing data to be collected in the laboratory. A test article of in-terest is placed under the sensor system, which is physically translated over the test article while collecting hyperspec-tral data. The test article can be an opaque material (e.g., sand, concrete, a human) or a transmissive material (e.g., clothing, vegetation). This laboratory sensor capability uses Aerospace’s Spatially Enhanced Broadband Array Spectro-graph System (SEBASS) to collect spectral-spatial data in the midwave infrared (2.5–5.5 micron) and the long-wave infrared (7.5–13.5 micron) regions. Two spatial dimensions of data are collected by physically translating a wide array detector in a direction perpendicular to the width of the ar-ray. External optics are mounted to the SEBASS aperture to change the focus of the instrument to a distance of 1 meter from the sensor. National Institute of Standards and Tech-nology–traceable thermal sources are used for calibrating the SEBASS instrument. A test article is either heated or illuminated using controlled thermal sources.

T. J. Grycewicz, “Methods for Estimating Peak Location on a Sampled Surface with Improved Accuracy and Applications to Image Correlation and Registration,” U.S. Patent No. 8,306,274, November 2012

Two methods commonly used to estimate the interpixel lo-cation of the peak value on a curve or surface are centroid-ing and curve fitting. In centroiding, a weighted average of the sample values near the peak location is used to find the center of mass of the peak. In curve fitting, the data points near the peak are approximated by a mathematical curve or surface with a known center point. These methods are sub-ject to inaccuracies for a number of reasons. Chief among them are that the data are noisy; a limited number of points are used for the estimate; and the real-world signal is not a perfect match to the mathematical surface used for fit-ting. In this invention, methods and systems for estimat-ing peak location on a sampled surface (e.g., a correlation surface generated from pixelated images) use one or more processing techniques to determine multiple peak location estimates for at least one sampled data set at a resolution smaller than the spacing of the data elements. Estimates selected from the multiple peak location estimates are then combined to provide one or more refined estimates. In the example of embodiments, multiple refined estimates are combined to provide an estimate of overall displacement (e.g., of an image or other sampled data representation of an object).

D. A. Ksienski, W. L. Bloss, E. K. Hall, and J. P. McKay, “Hep-tagonal Antenna Array,” U.S. Patent No. 8,314,748, Novem-ber 2012

It is ideal to provide an optimal packing density antenna array with good sidelobe rejection when both mechanical and electrical steering are at the same offsets. However, cur-rent antenna arrays only offer modest sidelobe rejection. This invention is directed to a heptagonal antenna array offering improved sidelobe rejection. For reasons not yet fully understood, an unexpected and surprising discovery was made that an eight-element array, having one center element and seven exterior elements circumferentially sur-rounding the center element, has superior sidelobe rejec-tion performance, even with an increase in interelemental spacing. That is, sidelobe rejection is improved, surpris-ingly, in both the near and far sidelobes, yet the packing density has been modestly degraded over the hexagonal configuration. The system uses a heptagonal arrangement in an eight-element array. The suppression of the sidelobes relative to peak gain of the main beam has been improved to –15 decibels.

J. A. Conway, J. V. Osborn, and R. A. Stevenson, “Plasmon Sta-bilized Laser Diodes,” U.S. Patent No. 8,325,776, December 2012

The conventional high-power laser diode does not fill its laser gain cavity during standard operation. Instead, the optical mode forms a filament from the optical and gain dynamics of the device. The position of this lasing filament is not static but rather moves through the device, creating multimodal hot spots and thermal lenses that accelerate failure of the device. This invention is directed to a large area laser having a plasmonic reflector. The plasmonic re-flector redistributes the lateral mode profile within the laser diode to advantageously reduce the potential for filamented or confined lasing and the consequential hot spots within the laser diode. The plasmonic reflector serves to control the diffusion of the optical field by redistribution, as being diametrically opposed to the focusing, for mode spoilage, mode expansion, or all of these. The reflector is preferably a patterned metal film disposed in a multitransverse-mode laser diode for redistributing the reflected light for control-ling spatial, polarization, and spectral parameters of the laser light. The reflector is used for generating free-space laser exit beams by expanding, shaping, or manipulating the laser light within the laser diode.

S. W. Janson, “Propulsion Systems and Methods Utilizing Smart Propellant,” U.S. Patent No. 8,336,826, December 2012

Rocket propulsion is based on the high-speed ejection of propellant mass. Conventional propellant mass, once ejected, does not return, and available propellant mass decreases with each propulsive maneuver. This invention



is based on the ejection of “smart propellant devices,” indi-vidual propellant masses that can fine-tune their trajectory after ejection at specific velocities to return to the spacecraft for reuse. In many cases, such as orbit rephasing maneu-vers, the returning smart propellant provides an additional beneficial impulse. Smart propellant is composed of in-dividual small spacecraft (e.g., pico- or nanospacecraft) with navigation determination, attitude determination and control, and propulsion systems. In example embodiments in which the ejected smart propellant device returns to the spacecraft and is recaptured, the smart propellant device, less any onboard propellant mass expended for trajectory modification, can be reused again and again. This enables new space mission capabilities such as reuseable lunar landers.

K. Siri, “Current Sharing Power System,” U.S. Patent No. 8,351,229, January 2013

Isolated ac-to-dc power systems with active power fac-tor correction have been used in several applications for drawing sinusoidal currents from utility grids or input ac power sources, and regulation of dc output voltages being isolated from the grid or the input power sources. With-out active current sharing, parallel connection of these identical power systems, respectively at their ac inputs and dc outputs, is not feasible as a result of nonuniform cur-rent sharing among the paralleled power channels. When parallel-connected, only one or a few power channels have a dominant power contribution while the remaining power channels are idle or make small contributions to the common output load. In many cases, the oversubscribed power channels have increased unreliability and short-ened lifetimes from persistent thermal overstresses. This invention includes multiple channels, and each channel has a current-sharing controller that is coupled to a shared current signal bus and a shared voltage signal bus. As a consequence of multiple current-sharing controllers with the two commonly shared buses, multiple power channels of an ac-to-dc converter power system with active power factor correction can be parallel connected to achieve uni-form power sharing and input/output electrical isolation without conflicts in the system output voltage regulation. The parallel-connected source or independent ac power sources may possess different frequencies, phases, and voltages. Current-sharing control approaches are blended with existing control of back-end commercial-off-the-shelf converters. Here, the converter outputs are parallel con-nected across a common load, and uniform current shar-ing among the channel-output currents is achieved while maintaining output voltage regulation performance. These control approaches are also applicable to distributed ac power sources, each of which is independently connected to the input of the respective ac-to-dc power channel, re-sulting in multiple channels of distributed ac-to-dc power

systems that equally share their power flows into the same load.

A. W. Bushmaker, “Systems, Methods, and Apparatus for Gen-erating Terahertz Electromagnetic Radiation,” U.S. Patent No. 8,357,919, January 2013

Terahertz (THz) radiation refers to electromagnetic waves propagating at frequencies between the infrared and microwave regions of the spectrum, generally 0.3–3 THz. Despite the promising applications of this technology, the availabil-ity of compact, reliable sources of THz waves is still limited. This invention for generating THz waves involves coupling a terahertz electromagnetic resonator with an optical reso-nator, where the optical resonator is made from nonlinear optical material. Directing laser light through the optical resonator generates THz radiation by parametric interac-tion of the two resonators through the nonlinear material. In a preferred implementation of this invention, a Fabry-Pérot optical resonator is placed in the electrode gap of a metallic split-ring THz resonator.

M. H. Abraham and D. P. Taylor, “Systems and Methods for Preparing Freestanding Films Using Laser-Assisted Chemi-cal Etch, and Freestanding Films Formed Using Same,” U.S. Patent No. 8,368,155, February 2013

Laser-assisted chemical etch (LACE) may involve exposing a structure that includes a substrate and a film to a chemi-cal etchant, such as chlorine gas, and to light. The substrate may be selectively etched in regions exposed to the light and to the chemical etchant, thus creating a cavity that frees the film from the substrate in a selected region. However, only selected types of structures have been prepared thus far using LACE. Other references disclose forming chan-nels in substrates beneath surface films, also by exposing such structures to an etchant and to light. The structures prepared using such methods are limited in the type of channel that may be formed and/or the quality of the surface film remaining after processing. In this invention, freestanding films are prepared by diffusively delivering an etchant to the substrate through a surface film while transmitting laser light to the substrate via the surface film. Together, the etchant and the laser light isotropically define a cavity in the substrate beneath the surface film. The dif-fusive nature of the etchant delivery obviates the need to provide access holes through the film, which may other-wise detrimentally affect the structural integrity of the film. In other embodiments, the freestanding films have any of a variety of suitable compositions besides silicon dioxide or silicon nitride. For example, the films may be multilayer films and/or may include hafnium oxide, diamondlike car-bon, graphene, or silicon carbide of a predetermined phase. Such films may include access holes defined to facilitate etching of the underlying substrate.


T. Grycewicz, “Imaging Geometries for Scanning Optical De-tectors with Overlapping Fields of Regard and Methods for Providing and Utilizing Same,” U.S. Patent No. 8,368,774, February 2013

Overlapped (i.e., staggered) time delay and integrated (TDI) scanning arrays with interlaced columns can provide up to twice the effective resolution of conventional TDI focal plane arrays with the same pixel size when operated under nominal conditions. However, especially when the overlapped TDI arrays are physically separated on the camera focal plane, image drift can destroy the alignment that allows for superresolution reconstruction of the over-lapped images. It would be useful to be able to decrease the susceptibility of overlapped TDI arrays (or other optical detectors arranged with overlapping fields of regard) from loss of high-resolution performance in the presence of im-age drift. It would also be beneficial to be able to improve the tolerance of overlapped-array imaging technologies to scan rate errors. In addition, it would be useful to be able to minimize (or decrease) the conditions under which im-age drift results in severe degradation of the resolution gain potentially realized from the use of staggered arrays. In this invention, imaging devices and techniques use multiple optical detectors, and, in particular, imaging geometries, for imaging devices that include three or more optical detectors with overlapping fields of regard. The imaging geometries are determined and provided in consideration of one or more performance criteria evaluated over mul-tiple operating conditions for the process of generating a reconstructed image from the captured images. Example embodiments involve arrangements of subpixel spacing for overlapped imaging arrays (or other optical detectors arranged with overlapping fields of regard) that decrease the susceptibility of the overlapped arrays to loss of high-resolution performance in the presence of image drift. By way of example, physical and/or virtual arrangements of subpixel spacing of three or more overlapped imaging ar-rays are determined in consideration of a process in which an image is generated (e.g., reconstructed) from outputs of three or more imaging arrays.

H. Helvajian, W. W. Hansen, and L. F. Steffeney, “Photostruc-tured Electronic Devices and Methods for Making Same,” U.S. Patent No. 8,369,070, February 2013

Photostructurable glass ceramic materials are used to make structures that have internal functional surfaces, which are defined during or after the photostructuring process. A number of approaches are possible and depend on the material constituents and concentration. If the material has a high-enough metal concentration, then conducting lines can be directly precipitated from the glass by a laser direct-write patterning technique. An alternative approach is to fill a photostructured cavity with gases that, under ultraviolet light or high temperature, produce photolyse/

pyrolize electrically conducting material. The cavity can also be filled by a conducting paste that is forced into the channels by applied pressure through hydraulic action. The three-dimensional electrically conducting structures are encapsulated within an electrically insulating shell. One practical example is in the use of electromagnetic applica-tions (i.e., complexly shaped antennas for high-frequency applications) where the delicate electrically conducting antenna structure formed is surrounded by an insulating package that protects it, but also has low radio-frequency attenuation.

C. C. Reed, T. R. Newbauer, and R. Briet, “Computer-Imple-mented Systems and Methods for Detecting Electrostatic Discharges and Determining Their Origination Locations,” U.S. Patent No. 8,370,091, February 2013

Electrostatic discharges (ESD) on solar cells are triggered when electrical field strengths become high enough to induce the transport of charges. Subsurface blisters, voids, and other manufacturing defects, as well as metal whiskers, can, in a charging environment, produce the field strengths needed to induce an electrostatic discharge. Micrometeor-oid impacts are another potential trigger for ESD. Similar mechanisms apply to other exposed satellite surfaces. No viable techniques for locating the origination point of ESD events have been implemented, yet knowing where ESD events originate from would be useful in developing miti-gation of anomalies from ESD on future space systems, and in improving operating procedures of current and future space systems. This invention is directed at computer-implemented systems and methods for detecting ESD on a surface, and determining the original location of an ESD. The surface may be, for example, a solar panel. In various embodiments, a programmed computer device monitors time-varying current data (i.e., current transients) related to the surface to detect ESD on the surface. Also, the cur-rent profile or signature for the surface (i.e., the variation of current level over a time period) may be compared to a cat-alog of ESD current profiles, where each ESD profile corre-sponds to a different location on the surface (e.g., the solar panel). The location on the surface whose corresponding ESD current profile best matches the actual current profile from the ESD determines the original location of the ESD. Moderately different processes may be used to determine the ESD originating location depending on the shape of the surface (i.e., whether it is symmetrical or irregular, or flat or curved in three dimensions).

G. Radhakrishnan and P. M. Adams, “Method for Growth of High-Quality Graphene Films,” U.S. Patent No. 8,388,924, March 2013

Existing methods for making graphene include exfoliation from highly oriented pyrolytic graphite, desorption of sili-con from silicon carbide single crystals, and chemical vapor


deposition from gaseous methane/hydrogen mixtures. These methods, however, have limitations because they do not offer large-area, single-layer graphene or produce graphene with small single-crystal grains, which results in numerous grain boundaries. Thus, there exists a need for alternative methods for large-scale synthesis of monolayer graphene over large areas that would be highly ordered and would have large single-crystal grains. This inven-tion addresses these needs by producing a highly ordered, single-layer graphene film with large single grains of 10–30 square microns. According to this method, graphene films are formed on a substrate held in a heated reactor using an inert buffer gas to transport vapor from an oxygen-contain-ing liquid hydrocarbon precursor, such as methanol, over the heated substrate.

S. W. K. Yuan and D. G. T. Curran, “Variable Phase Shift De-vices for Pulse Tube Coolers,” U.S. Patent No. 8,408,014, April 2013

Pulse tube cryocoolers do not have moving parts at the cold end, such as displacer pistons or valves. To achieve the desired cooling, the combination of the phase control device and the reservoir causes a phase shift between mass waves and pressure waves generated by the compressor. By restricting or slowing the mass flow to the buffer volume, the phase control device may serve to shift the phase of the mass flow relative to the pressure wave generated by the compressor. This invention is directed to pulse tube coolers that have flow resistance devices that are variable within the thermodynamic cycle of the pulse tube. An example pulse tube may be comprised of a compressor, regenerator, and reservoir. A working fluid may be positioned within the regenerator, pulse tube, and reservoir. Further, a vari-able phase control device may be positioned in a fluid path between the pulse tube and the reservoir. The pulse tube cooler may also have a control circuit. The control circuit may be programmed to determine a position of the pulse tube cooler in its thermodynamic cycle and vary a char-acteristic of the variable phase control device based on the position of the pulse tube cooler in its thermodynamic cycle.

R. Kumar, “Receiver for Detecting Signals in the Presence of High-Power Interference,” U.S. Patent No. 8,433,008, April 2013

Command and telemetry constitute two of the most impor-tant subsystems of the U.S. Air Force space lift range sys-tem, which is designed to provide operational support for space launch vehicles. A command destruct signal (CDS) is sent to the launch vehicle if the trajectory of the vehicle poses any serious safety concerns. While the need to issue a CDS command happens infrequently, safety considerations require that this signal/link have high reliability under all conditions. It is also necessary to ensure that the command

uplink can be closed with sufficient margin under the worst possible conditions and from any intended launch sites. Under normal operating conditions, when the only significant disturbance is the receiver thermal noise, there is no real concern in terms of providing such a margin, as has been shown in previous analyses. However, in the pres-ence of high-power pulse interference, the performance of the traditional command receiver is very poor in that there is virtually no detection possible with such a receiver. In one aspect, the present invention is directed to a radio frequency (RF) receiver for CDS, although it could be used to receive different types of signals as well. According to various embodiments, the RF receiver is comprised of an RF section, a down converter to intermediate frequency, a down converter to complex baseband, a pair of analog-to-digital converters, and a digital signal processor (DSP). The DSP processes the complex baseband signal available at the output of the down converter to complex baseband so as to optimally estimate the amplitudes of various character tones and the pilot tones that are present in the CDS sig-nal, along with estimates of the associated signal-to-noise power ratios for the various tones.

M. P. Ferringer, R. S. Clifton, and T. G. Thompson, “Systems and Methods for a Core Management System for Parallel Processing of an Evolutionary Algorithm,” U.S. Patent No. 8,433,662, April 2013

The goal of multiple-objective optimization, which is in stark contrast to single-objective, where the global opti-mum is desired (except in certain multimodal cases), is to maximize or minimize multiple measures of performance simultaneously, maintaining a diverse set of Pareto-optimal solutions. Classical multiple-objective optimization tech-niques are advantageous if the decision maker has some prior knowledge of the relative importance of each objec-tive. Despite these advantages, real-world problems, such as satellite constellation design optimization and airline network scheduling optimization, challenge the effective-ness of classical methods. When faced with a discontinuous and/or nonconvex objective space, not all Pareto-optimal solutions may be found. Additionally, the shape of the front may not be known. These methods also limit dis-covery in the feasible solution space by requiring that the decision maker apply some sort of higher-level informa-tion before the optimization is performed. Furthermore, only one Pareto-optimal solution may be found with one run of a classical algorithm. According to this invention, there is a method for parallel processing of an evolution-ary algorithm. The method may include identifying by a manager processor for a processing environment a plural-ity of arriving processors available for use; configuring by the manager processor a first number of the plurality of arriving processors as master processors for the processing environment; configuring by the manager processor a re-



spective second number of the plurality of arriving proces-sors as slave processors; and reconfiguring by the managing processor a current number of slave processors assigned to one or more respective master processors based upon the respective timing data calculated for the one or more respective master processors.

N. P. Wells and J. C. Camparo, “Systems and Methods for Sta-bilizing Laser Frequency Based on an Isoclinic Point in the Absorption Spectrum of a Gas,” U.S. Patent No. 8,442,083, May 2013

One system in which frequency stabilization may be use-ful is ultraminiature atomic physics (UAP), in which diode lasers are routinely used for spectroscopy and/or optical pumping. The chip-scale atomic clock and the chip-scale atomic magnetometer are examples of UAP systems. One problem with such systems is that their overall size and power may be severely constrained. Moreover, the atomic phenomena may occur under physical conditions that may bring new and sometimes significant dimensions to the atomic physics as compared to macroscopic laboratory experiments. As such, the stability of the laser frequency in some circumstances may be critical, not only because variations in frequency yield variations in the spectroscopic signals of interest, but also because shifts in laser frequency may alter the atoms’ energy-level structure through a light-shift effect. For this invention, the isoclinic point is a point in the absorption spectrum of a gas that falls in between two overlapping absorption peaks of substantially equal amplitude, and which experience substantially the same broadening as a function of a physical parameter. Because the two peaks have equal amplitude, the isoclinic point is a saddle point (local minimum) in the region of overlap between the two peaks. As the peaks are evenly broadened from a change in the physical parameter, the frequency of the isoclinic point does not significantly change, but instead remains at a constant frequency, independent of the physical parameter. As such, by locking the laser to the frequency of the isoclinic point, the laser is significantly less susceptible to frequency variations than if the laser were locked to an absorption peak.

J. T. Chou, T. S. Rose, and J. A. Conway, “Time-Domain Gated Filter for RF Communication Systems,” U.S. Patent No. 8,443,024, May 2013

This invention is a photonic method for generating single sideband (SSB) modulated radio frequency (RF) signals, thereby reducing bandwidth requirements of system com-ponents. Simple modulation of an RF signal onto an optical carrier generates upper and lower sidebands. The double sideband (DSB) signal requires the system bandwidth to accommodate twice the frequency range of the imparted information or modulation. There are two primary meth-ods to achieve SSB modulation: phase discrimination and

optical filtering. In the phase discrimination approach, an RF hybrid coupler and balanced optical modulator are re-quired. The full bandwidth capability of available RF hybrid couplers, however, is limited to 10 seconds of gigahertz. Greater bandwidths can be achieved using optical filtering approaches. In the simplest approach, the DSB RF signal is imposed on an optical carrier and passed through an optical filter to remove the upper or lower sideband. This filtering method, however, is possible only when the optical carrier frequency is fixed and stable. In the time domain filter approach, the DSB signal is first given a chirp (the carrier frequency is given a linear frequency sweep) and then passed through a compressor. The compressor creates a time-domain image of the frequency spectrum so that the upper- and lower-frequency sidebands are separated in time. This signal passes through a time gate that removes one of the sidebands. The resulting signal is then sent through an expander to recreate the original modulated signal with one frequency sideband removed. As such, the time domain filter converts a DSB signal input into an SSB signal output.

S. La Lumondiere, T. Yeoh, M. S. Leung, N. A. Ives, W. T. Lot-shaw, and S. C. Moss, “Refraction Assisted Illumination for Imaging,” U.S. Patent No. 8,450,688, May 2013

One method of imaging through substrate material is con-ventional bright field microscopy. According to bright field microscopy, illumination is provided in a direction normal to the substrate surface. An image is captured with a cam-era or other imaging device that is also oriented normal to the substrate surface. While this technique can be relatively inexpensive, the resolution of the resulting images is often disappointing. The resolution of bright field microscopy can be enhanced by applying an antireflective coating to the substrate. This method, however, is expensive and re-quires that the target semiconductor chip be subjected to one or more additional processing steps. This invention is directed to systems and methods of imaging subsurface features of objects. An illumination source may be directed toward a surface of an object comprising subsurface fea-tures, wherein the illumination from the source is directed at a first angle relative to the normal area of the surface. The object may have a portion between the subsurface fea-tures and the surface, with the portion having an index of refraction that is greater than the medium surrounding the object. An imaging device may be placed with an objective lens oriented normal to the surface. The first angle may be larger than an acceptance angle of the objective lens.

F. T. Sasso and W. H. Chung, “High Frequency, Hexapod Six Degree-of-Freedom Shaker,” U.S. Patent No. 8,453,512, June 2013

State-of-the-art gyroscopes for space and other applications require realistic laboratory environments to test and char-



acterize performance. One popular type of gyro for space applications is fiber optic gyros, which have recently been found to be susceptible to low-level vibration. This effect manifests itself as abrupt shifts in bias, which can be detri-mental to operations. This phenomenon was not identified using standard gyro test techniques and has been shown to be extremely nonlinear. This invention is directed to a shaker for enabling the testing of gyros and other devices for performance under realistic six-degrees-of-freedom motions (e.g., spacecraft motions). The shaker may be implemented as a hexapod, comprising a top plate and six individually and simultaneously controllable strut assem-blies that are capable of extending and contracting linearly. The strut assemblies can then be controlled by a closed-loop, programmable controller to enable the plate to move linearly in all three directions and rotate about all three axes. The strut assemblies may comprise high-precision, linear electromagnetic actuators, such as voice coil actua-tors. The strut assemblies may also comprise high-precision noncontact sensors to sense the extension/contraction of the strut assemblies along their stroke length. In addition, the strut assemblies may comprise, at each end thereof, stiff, bendable flexures to attain the repeatable and linear motion required.

C. C. Reed and R. Briet, “System and Method for Detecting Defects,” U.S. Patent No. 8,466,687, June 2013

During or after the manufacture of an article, defects may be found that are difficult to detect from a visual inspec-tion of the article’s exterior. In some cases, the defects are present under an exterior surface of the article, such as a surface coating. Subsurface defects and other types of hard-to-observe flaws may have a number of undesirable conse-quences. In space systems, subsurface defects may degrade thermal control surfaces because of compromised paint; increase the likelihood of electrostatic discharges (ESD) on satellites; diminish ESD mitigation on solar cells from coat-ing loss; permit contamination of optical components from surface peeling and flaking; or cause rocket motor failure because of delamination of composite materials. Thermog-raphy is one example of a nondestructive evaluation and testing (NDET) technique for detecting subsurface defects. Thermographic techniques generally involve subjecting a test article to a thermal pulse followed immediately by an examination/evaluation of surface temperature differences using an infrared camera. A possible disadvantage is that the thermal pulse may cause new defects if the test article contains volatile materials in microcracks, or if the compo-sition of the test article includes materials with mismatched coefficients of thermal expansion. More benign NDET techniques are desirable. In this invention, various aspects of a nondestructive evaluation and testing system, includ-ing a charge source and at least one voltage measurement device, are disclosed. The charge source is for generating a

charging environment to produce either a voltage profile and/or a current on an area of dielectric material disposed over a conductive substrate. The area of dielectric mate-rial includes one area containing a subsurface defect and a second area that is defect-free. The voltage measurement device is for outputting voltage measurements at different positions over the area of dielectric material. The voltage measurements over the first area differ from the voltage measurements over the second area to define a voltage differential, and the locations where this voltage change oc-curs identify the boundary of the defect.

J. J. Poklemba, “Systems and Methods for Sliding Convolution Interpolating Filters,” U.S. Patent No. 8,489,662, July 2013

Digital data transmission systems have traditionally been designed for specific applications to accommodate rela-tively narrow ranges of data rates. Continuously variable rate transmitter and receiver systems, however, could provide certain desirable flexibilities. Unfortunately, to ac-commodate flexible up-sampling on the transmitter side or down-sampling on the receiver side, traditional data transmission systems have grown in size and hardware complexity. Hence, the classical hardware solution may experience an order of magnitude growth for each factor of ten increase in the sample rate. Another popular alternative to alleviate impractical hardware growth is the repeated use of commonplace, multiply-accumulate (MAC) functions in digital signal processing. However, this technique alone re-quires that the MAC run at integer multiples of the sample rate, greatly restricting top-end speeds. A need remains for improved systems and methods for up-sampling filters. According to this invention, a system is provided for imple-menting a multirate digital interpolating filter. The system includes a memory for storing finite impulse response (FIR) aperture coefficients for spectral shaping. The system also includes a processor configured to access the memory, which is configured to up-sample symbol data, wherein up-sampling comprises: convolving the symbol data with a decimated FIR aperture coefficient set; convolving the sym-bol data with one or more shifted, decimated FIR aperture coefficient sets; and summing up the convolution results to produce interpolated, bandlimited data. The system also includes an upconverter to modulate the interpolated, bandlimited data.

M. P. Ferringer and T. G. Thompson, “Systems and Methods for Generating Feasible Solutions from Two Parents for an Evolutionary Process,” U.S. Patent No. 8,494,988, July 2013

The goal of multiple-objective optimization, in stark contrast to the single-objective case where the global opti-mum is desired (except in certain multimodal cases), is to maximize or minimize multiple measures of performance simultaneously while maintaining a diverse set of Pareto-optimal solutions. Classical multiple-objective optimiza-


tion techniques are advantageous if the decision maker has some prior knowledge of the relative importance of each objective. But despite these advantages, real-world problems, such as satellite constellation design optimiza-tion, challenge the effectiveness of classical methods. These methods also limit discovery in the feasible solution space by requiring the decision maker to apply higher-level information before the optimization is performed. This invention may include: receiving a pair of parent chromo-some data structures where each parent chromosome data structure provides a plurality of genes representative of variables that are permitted to evolve; combining genes of the two parent chromosome data structures according to at least one first evolutionary operator to generate at least one first child chromosome data structure; evaluating at least one first child chromosome data structure according to a plurality of constraint functions to generate a respective plurality of constraint function values for each of the first child chromosome data structures, where the constraint functions define constraints on a feasible solution set; de-termining whether any of the first child chromosome data structures is within the feasible solution set based upon the respective plurality of constraint function values, where the prior combining, evaluating, and determining steps are repeated for a number of first iterations until a first child chromosome data structure is determined to be within the feasible solution set or until a first maximum number of first iterations has been reached.

M. P. Ferringer and T. G. Thompson, “Systems and Methods for Box Fitness Termination of a Job of an Evolutionary Software Program,” U.S. Patent No. 8,498,952, July 2013

The goal of multiple-objective optimization, in stark contrast to the single-objective case where the global opti-mum is desired (except in certain multimodal cases), is to maximize or minimize multiple measures of performance simultaneously while maintaining a diverse set of Pareto-optimal solutions. Classical multiple-objective optimiza-tion techniques are advantageous if the decision maker has some a priori knowledge of the relative importance of each objective. However, despite these advantages, real-world problems, such as satellite constellation design optimiza-tion, challenge the effectiveness of classical methods. These methods also limit discovery in the feasible solution space by requiring the decision maker apply some sort of higher-level information before the optimization is performed. This invention may include: receiving a respective plural-ity of objective function values for each chromosome data structure of a population of chromosome data structures, where the respective plurality of objective function values are obtained based upon an evaluation of each chromo-some data structure by a respective plurality of objective functions; mapping the respective objective function values to respective epsilon values, where the respective epsilon

values define a respective address associated with the plu-rality of objective functions; performing nondomination sorting of the population of chromosome data structures to generate a reduced population of chromosome data struc-tures based upon an evaluation of the respective plurality of objective function values; and performing epsilon non-dominated sorting according to an optimization of the plu-rality of objective functions and the defined respective ad-dresses to identify an elite set of addresses, where the prior steps are performed for a current generation, where the elite set of addresses are compared to a prior elite set of ad-dresses for a predetermined number of prior generations to determine one or more variance values, and where the one or more variance values are utilized to determine whether a current job of an evolutionary algorithm is to be halted.

M. P. Ferringer, R. S. Clifton, and T. G. Thompson, “Systems and Methods for an Application Program Interface to an Evolutionary Software Program,” U.S. Patent No. 8,504,496, August 2013

The goal of multiple-objective optimization is to maximize or minimize multiple measures of performance simultane-ously while maintaining a diverse set of Pareto-optimal solutions. Classical multiple-objective optimization tech-niques are advantageous if the decision maker has some prior knowledge of the relative importance of each objec-tive. Because classical methods reduce the multiple-objec-tive problem to a single objective, convergence proofs exist assuming traditional techniques are employed. However, despite these advantages, real-world problems, such as sat-ellite constellation design optimization and airline network scheduling optimization, challenge the effectiveness of clas-sical methods. This invention may include a memory for storing computer-executable instructions for an application program interface, and a processor in communication with the memory. The processor may be configured to execute the computer-executable instructions to enable a user of the application program interface to: specify parameters associated with an evolutionary algorithm, where an execu-tion of the evolutionary algorithm is in accordance with the specified parameters; define a chromosome data structure that includes a plurality of variables that are permitted to evolve in value in accordance with the execution of the evolutionary algorithm to generate one or more child chromosome data structures; identify one or more objec-tive functions for evaluating chromosome data structures, including the generated one or more child chromosome data structures; and define an output format for providing one or more optimal chromosome data structures of the evaluated generated child chromosome data structures as designs to the identified objective functions.

K. Chiou and S. L. Osburn, “Systems and Methods for an Ad-vanced Pedometer,” U.S. Patent No. 8,510,079, August 2013



Some prior pedometers estimate the distance traveled by counting the number of steps and multiplying by an aver-age person’s stride length. However, nonstandard stride lengths and a variety of other factors are sources of error in the estimated distance traveled. Other pedometers use accelerometers and a barometer to estimate the distance of each step. However, these pedometers do not provide calibration for accelerometer drift, and thus, the accuracy of the measured steps varies greatly over time. Some or all of the above needs and problems may be addressed by this invention. According to this invention, the advanced pe-dometer can include a first accelerometer for providing first acceleration information for a first direction; a second ac-celerometer for providing second acceleration information for a second direction; a third accelerometer for providing third acceleration for a third direction, wherein the first, second, and third directions are independent of each other; a clock for providing time information associated with the first, second, and third acceleration information; and a processing module comprising one or more processors. The processing module is configured to receive the first, second, and third acceleration information, and is further configured to execute computer-executable instructions to determine fourth-level acceleration information for a plane using the first acceleration information for the first direction and the second acceleration information for the second direction, wherein the plane is defined by the first direction and the second direction, and estimate a distance traveled using the fourth-level acceleration information, the third acceleration information, and at least a portion of the time information. This invention uses a zero velocity filter update to reduce drift between steps, and, rather than counting steps or attempting to dead reckon in three-space, the method of this invention integrates the distance trav-eled along a curvilinear path, similar in concept to the way a car odometer measures the distance traveled by a car.

P. A. Dafesh, R. S. Prabhu, and E. S. Valles, “Cognitive Anti-Jam Receiver Systems and Associated Methods,” U.S. Patent No. 8,515,335, August 2013

Existing antijam and interference mitigation techniques are based on the assumption that the nature of interference is previously known. Thus, these existing techniques use fixed antijam and interference mitigation techniques. However, these fixed techniques are not well suited in situations where the nature of the interference changes unpredictably or where the nature of the interference is not previously known. According to this invention, a cognitive antijam receiver system may include a signal analysis module that processes a baseband signal to determine one or more signal characteristics of the signal; a cognitive decision unit that receives one or more signal characteristics from the signal analysis module and generates at least one first adaptive parameter; and an antijam processing module

that processes the baseband signal to generate a modified signal that reduces the impact of the jammer signal on the quality of reception of the desired signal from the baseband signal, where processing by the antijam processing module is based on the received first adaptive parameter from the cognitive decision unit. The system may also include the cognitive decision unit further generating a second adap-tive parameter, and a receiver signal processing module that processes the modified signal from the antijam pro-cessing module to extract information about the desired signal from the modified signal, where processing by the receiver signal processing module is based on the received second adaptive parameter from the cognitive decision unit.

A. J. Gallagher, “Methods and Systems for Detecting Tempo-rally Oscillating Sources in Video Signals Using a Recursive Infinite Impulse Response (IIR) Filter Technique,” U.S. Pat-ent No. 8,532,197, September 2013

In recent years, the availability of high-speed general-purpose computing systems and digital video recorders has allowed the advancement of techniques for detecting and finding scene content in video sequences. The fast Fourier transform (FFT) is a well-known and widely used tech-nique for decomposing signals into periodic components and has been employed extensively in the realm of signal processing, to include cases where the signal consists of a single image pixel with time-varying amplitude. However, in the case of imagery and video, where charge-coupled device arrays can include very large numbers of pixels, the FFT method applied to each pixel vector becomes computationally expensive. Moreover, if FFT were applied to temporal video analysis, using the full FFT for signals with known periodic structure would result in a signifi-cant waste of computation time on irrelevant frequency components. It would be useful to be able to provide scene content detection methods and systems that overcome one or more of the deficiencies of prior approaches to temporal video analysis. The methods and systems of this invention facilitate detection of temporally oscillating sources in digi-tal video signals. Such methods and systems can be imple-mented to provide temporal target detection, as well as target localization, tracking, tagging, identification, status indication, and low-rate data transfer. Additional applica-tions for the techniques include object recognition, pixel classification, scene analysis, computer vision, and robot vi-sion, as well as any process involving a video reference from which it is desirable to extract one or more modulation frequencies from the video data.

S. W. Janson and J. K. Fuller, “Systems, Methods, and Appara-tus for Sensing Flight Direction of a Spacecraft,” U.S. Patent No. 8,538,606, September 2013


Small satellites have low weights and small sizes, to reduce launch cost to orbit. A 1 unit CubeSat, for example, weighs about 1 kilogram, occupies a volume of about 1 liter, and has a limited amount of available room for auxiliary sys-tems, such as a flight direction sensor system for efficient orbital positioning. Previous approaches to flight direction sensing have involved calculation of the satellite attitude via combinations of sun, star, Earth horizon, and other sensors. However, such approaches often require multiple sensors and complex imaging systems that can be prohibitively bulky. The atmosphere rotates with the planet, so space-craft in low Earth orbit fly through this atmosphere at 7 to 8 kilometers per second. Pressure-sensing approaches to determining flight direction include direct physical sens-ing of the pressure difference between leading and trail-ing edges of the spacecraft, or monitoring neutral wind direction. These approaches work best at low (less than 500 kilometer) altitudes where the atmospheric density is readily detectable. However, the atmospheric density drops rapidly with increased altitude, and therefore, detecting flight direction using pressure sensing becomes almost im-possible at altitudes greater than 1000 kilometers. Accord-ing to this invention, a system is provided for determining flight direction of a spacecraft. The system includes a nadir direction finder, a power source, an onboard gyroscope, and an imaging detector attached to the spacecraft. The imaging detector is configured to acquire sequential images of a portion of a celestial body, and further configured to process the sequential images. The system also includes a flight computer that is in communication with the imaging detector and configured to execute computer-executable instructions for determining the spacecraft flight direction relative to the celestial body, based in part on the process-ing of the sequential images.

R. J. Zaldivar and J. P. Nokes, “Hybrid Adhesive,” U.S. Patent No. 8,551,287, October 2013

The use of atmospheric plasma treatment process can be an excellent method for the surface preparation of graphite epoxy composites prior to bonding. However, many high-performance composite structures currently used for space applications use a cyanate ester matrix material, not epoxy. Cyanate ester composites have many improved properties when compared with epoxies used in similar applications. Unfortunately, studies show that the bond performance of plasma-treated cyanate ester composites do not improve to the same degree as select plasma-treated epoxies. The chemical structure that contributes to many of these im-proved properties makes cyanate ester resins more resistant to forming the bond-enhancing species. This invention describes how to fabricate a tailored hybrid composite sys-tem with improved bond performance, taking advantage of a secondary surface layer or film that is cocured with the substrate. The hybrid system is able to form higher concen-

trations of the bond-enhancing active species during at-mospheric plasma treatment than in the initial unmodified system. This hybrid adhesive improves bond performance without compromising the superior properties of cyanate ester composites.

T. J. Grycewicz, “System and Method for Super-Resolution Digital Time Delay and Integrate (TDI) Image Processing,” U.S. Patent No. 8,558,899, October 2013

In conventional time delay and integrate (TDI) process-ing, the image motion across the array must be parallel to the array columns to avoid image smear. Likewise, the image motion across the array must be precisely locked to the array line rate to avoid smear. According to this invention, image drift is deliberately introduced in both dimensions and output data are sent to a super-resolution processing algorithm, which uses this drift to produce an image with up to twice the effective resolution possible with a conventional TDI imager. The imaging geometry is set up such that a predictable subpixel component of the frame-to-frame image motion can be used to construct a high-resolution output image from multiple undersampled, low-resolution input images. This combines the benefits of TDI imaging with the benefits of super-resolution process-ing. In this invention, the TDI focal plane is rotated from its normal orientation perpendicular to the scan direction. This produces a predictable cross-scan drift. The line rate is set to produce an in-scan drift. During image collection, a sequence of images is saved, and the images are combined on a high-resolution synthetic image plane (by, e.g., using techniques developed for reconstruction of a high-reso-lution image from sequences of low-resolution images). When the image drifts are accurately known and easily controlled, image processing is easily and efficiently imple-mented, and the only additional resource required in the processing chain is more memory. Alternately, if the drift rates are not known or easily controlled, the image drift can be estimated for each subimage, and the image reconstruc-tion can be carried out as a postprocessing step.


CONTRIBUTORS

Think Big, Fly SmallCharles L. Gustafson, General Manager, Launch Systems Division, joined Aero-space in 1983. Today he manages launch system projects for a range of custom-ers, with a current principal activity being the certification of the SpaceX Falcon 9 (v1.1) system. He is a member of the Air Force Scientific Advisory Board and was formerly the general manager of the Vehicle Systems Division, and the principal director for the Transformation Communications Satellite Program (TSAT). He has a B.S. in electrical engineering from Princeton Uni-versity and an M.S. and Ph.D. in electrical engineering from the University of California, Berkeley.

Siegfried W. Janson, Senior Scientist, Physical Sciences Laboratories, joined Aerospace in 1987. He works on small satellite design, attitude sensors, and orbital architectures. He is the principal investigator on the NASA-sponsored Optical Communications and Sensors Demonstration, which is a high-speed laser communications downlink from a low Earth orbit CubeSat to the ground. He has a B.S. in astronautical engineering from Rensselaer Polytechnic Insti-tute and an M.S. and Ph.D. in aerospace engineering from Cornell University.

Internal Research and Development Spurs Advancement and Fills Technology GapsT. Paul O’Brien, Research Scientist, Space Sciences Department, joined Aero-space in 2002. He conducts scientific research into Earth’s radiation belts and magnetosphere. He also develops space environment models and tools for satel-lite design, situational awareness, and anomaly resolution. He has a B.A. degree from Rice University in physics and classics, and M.S. and Ph.D. degrees from UCLA in geophysics and space physics.

2025 and Beyond: The Next Generation of Protected Tactical CommunicationsJo-Chieh Chuang, Senior Project Leader, Emerging Systems, MILSATCOM Division, joined Aerospace in 1986. He has worked on several MILSATCOM architecture studies, the AEHF program, and the TSAT program. He is the Aerospace lead for the Air Force’s “Design for Affordability Risk Reduction” project to develop and demonstrate the protected tactical waveform and pro-tected tactical system concepts. He has a B.S. in mechanical engineering from the National Cheng-Kung University in Taiwan; an M.S. in mechanical engi-neering from the University of Texas at Arlington; and a Ph.D. in mechanical engineering from the University of Houston.

Joseph Han, Department Director, Network Systems, joined Aerospace in 1989. He leads and performs system-level analyses and designs for various communi-cation and network systems. He has a B.S. in electrical engineering from Soong Sil University, Korea; an M.S. in electrical engineering from California State University, Los Angeles; and a Ph.D. in electrical engineering from the Univer-sity of California, Irvine.

Siegfried W. Janson

Charles L. Gustafson

T. Paul O’Brien

Jo-Chieh Chuang

Joseph Han


Bomey Yang, Engineering Specialist, Communication and Network Architec-tures Subdivision, joined Aerospace in 2007. She leads and performs waveform analyses as well as communication systems design studies for various MILSAT-COM programs. She has a B.S. in computer science and engineering, and an M.S. in electrical engineering from the University of California, Los Angeles.

Applying Systems Engineering to Manage U.S. Nuclear CapabilitiesMatthew J. Hart, Principal Director, Civil Applications Directorate, Civil and Commercial Programs, joined Aerospace in 1987. He has 26 years of experience with the DOD, National Reconnaissance Office, and NASA, and currently man-ages the corporation’s support to a number of U.S. government civil customers. He has a B.S. in aeronautics and astronautics from Purdue University and an M.S. in aero-astronautics from Stanford University.

James D. Johansen, System Director, Department of Energy Programs, Civil and Commercial Programs, joined Aerospace in 2008. He previously worked at the MITRE Corporation, Lockheed Martin, and Boeing on space, terrestrial, and information technology programs. He manages the Department of Energy Programs Department and directs various interagency civil customer studies, analysis of alternatives, technology development activities, and enterprise ca-pability assessments. He has a B.S. and M.S. in electrical engineering from the University of Southern California.

Mark J. Rokey, Senior Project Engineer, Civil Applications Directorate, Civil and Commercial Programs, joined Aerospace in 2011. He has 26 years of expe-rience with NASA and leads system-level analyses for various government proj-ects. He has an M.S. in computer science from Texas A&M University.

Mark J. Rokey

James D. Johansen

Bomey Yang

Matthew J. Hart

Electric Propulsion at Aerospace

The Aerospace Corporation began the development of an elec-tronic propulsion (EP) testing capability in the 1980s that has since become one of the premier world facilities for the advanced characterization of EP thrusters.

These capabilities have been applied to two key Air Force pro-grams, Wideband Global Satellite Communication System (WGS) and Advanced Extremely High Frequency (AEHF). WGS flies on Boeing’s 702 bus using the XIPS 25 gridded ion engine manufac-tured by L3, and AEHF flies on Lockheed Martin’s A2100 bus using the XR5 (also known as BPT-4000) Hall thruster manufactured by Aerojet/Rocketdyne. Aerospace expertise and testing has provided mission assurance and anomaly resolution for these programs.

Aerospace is well known for advanced diagnostics applied to thruster characterization and their integration effects on space-craft, e.g., various plasma probes and laser-based plume measure-ments. Aerospace was the first to apply a number of diagnostic tools to the characterization of EP thrusters, perhaps most notably electromagnetic radiation measurements. The Aerospace Electromagnetic Interference Test Facility is unique in the world and draws to Aerospace virtually all flight thrusters for testing to ensure that thruster operations will not interfere with satellite communications. Consequently, Aerospace maintains the most comprehensive database on EP thruster measurements anywhere.

Recent work at Aerospace has ranged from the very practical, such as transitioning mature thruster designs to flight, to basic re-

search on improving the fundamental understanding of the plasma physics underpinning thruster operation. Recent collabo-rations with NASA Glenn Research Center have been critical in advancing NASA’s Evolutionary Xenon Thruster (NEXT) 7-kW ion engine to flight, as well as developing future higher-power an-nular ion engine designs.

Aerospace has also developed novel diagnostics for the character-ization of miniature electrospray thrusters developed at the Mas-sachusetts Institute of Technology for use on CubeSats. Aerospace is also a leader in characterizing facility effects on Hall thruster operation, which can severely hamper the ability to reliably predict on-orbit performance using ground-based test and qualification data.

Electric propulsion has come of age with recent announcements from a number of U.S. and international contractors developing an “all-electric bus” to provide mass/cost savings to customers. Aero-space has played an important historical role in the maturation of EP technology, and continues to advance the state of the art.

–Thomas Curtiss, director, Propulsion Science Department

Courtesy of NA

SA

The iEPS electrospray thruster.

Courtesy of the Massachusetts

Institute of Technology

The Aerospace electromagnetic interference test facility.

NASA's NEXT gridded ion engine.

Courtesy of NA

SA

NASA's annular ion engine.

The Aerospace Corporation’s picosatellite team captured these photographs (next page) shot from an unclassified AeroCube satellite last fall. The photos display some of

today’s advanced technologies and the functionality of miniature space components.

Picosats are being tested for use on many national security space missions. Their reduced cost and quicker turnaround to delivery make them a compelling and attractive choice for space customers. Small satellites cannot replace the capabilities of large satellites, but scientists and engineers continue to push the boundaries of what they can do, and explore how these miniature satellites may best serve the national security space community.

The AeroCube 4C is a 10 × 10 × 10 centimeter CubeSat built at Aerospace. This CubeSat contains various first-of-a-kind mission technologies including solar panel wings designed for efficient formation flying; attitude control to better than 3 degrees accu-racy; a 0.3 square meter deployable deorbit device; and subminia-ture reaction wheels.

Aerospace’s 2014 team of the year award went to the picosat team, whose 22 members were recognized for “consistently leading its field in innovation” and for “building groundbreak-ing spacecraft while meeting immensely restrictive budget and scheduling requirements.”

AeroCube 4C Delivers Stunning Photos

THE BACK PAGE

A. B.

E. F.

I. J.

A: Israel and SinaiB: The Great Barrier ReefC: JamaicaD: Baja California

E: New ZealandF: Himalaya MountainsG: Grand CanyonH: Los Angeles

I: Sahara’s EyeJ: DenaliK: Washington, D.C.L: Aerospace research scientist Brian Hardy examines images from space.

C. D.

G. H.

K. L.

The Crosslink Crossword

Across

1. Talk show big shot 3. Military supply center 5. Dramatic situation 6. Politician's plan 7. Three is this 9. Like Plastic Man? 11. Polite 13. Kind of (plastic) card 14. Speedster's sport 16. Freewheeling music session 19. Hearty 21. Postpone (an agenda item) 23. Apple infrastructure 25. Sonic phenomenon 26. Movie building block27. They're everywhere in L.A.29. Put down (money)30. Entrance31. With "in," contribute32. Airport building33. Move backwards34. Unclear mixup

Down 1. Beer plant 2. "Let me ___ your memory. 3. Supervisory body

Most puzzle words and clues are from articles in this issue. The solution is on the Crosslink Web site: http://www.aerospace.org/publications/crosslink/.

4. It's a long story 8. Amount of medicine 9. Investments carry this 10. "I'll huff & I'll puff..." 11. Vehicle for verse greetings

Editor-in-ChiefNancy K. Profera

Guest EditorJohn V. Langer

Contributing EditorsGabriel Spera

Richard K. Park

Staff EditorJon S. Bach

Research and Program Development Advisor

Terence S. Yeoh

Art Direction and DesignJason C. Perez

Richard M. Humphrey

IllustrationJason C. Perez

Joseph P. Hidalgo

PhotographyEric Hamburg Elisa Haber

Editorial BoardRandy M. Villahermosa, Chair

David A. BeardenKevin D. Bell

Walter F. BuellJohn E. Clark

Henry Helvajian Michael R. HiltonDiana M. Johnson

Jean L. MichaelMarilee J. Wheaton

Crosslink®

FALL 2014 VOL. 15 NO. 1

Board of TrusteesBarbara M. Barrett, Chair

George K. Muellner, Vice ChairWanda M. AustinKevin P. Chilton

David M. DiCarloMichael B. Donley

Bonnie DunbarKeith P. Hall

Daniel E. HastingsTina W. Jonas

John E. McLaughlinMichael Montelongo

Jeffrey H. SmithK. Anne StreetAlan C. Wade

Robert S. Walker

Corporate OfficersWanda M. Austin, President and CEO

Ellen M. Beatty Bernard W. Chau

Malissia R. ClintonManuel De Ponte

Rand H. Fisher Wayne H. Goodman

David J. GorneyMalina M. HillsRay F. Johnson

Randy L. KendallWilliam C. Krenz

Howard J. MitchellRami R. Razouk

Catherine J. SteeleSherrie L. Zacharius

Crosslink 20141 2 3

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Across1. Talk show big shot3. Military supply center5. Dramatic situation6. Politician's plan7. Three is this9. Like Plastic Man?

11. Polite13. Kind of (plastic) card14. Speedster's sport16. Freewheeling music session19. Hearty21. Postpone (an agenda item)23. Apple infrastructure25. Sonic phenomenon26. Movie building block27. They're everywhere in L.A.29. Put down (money)30. Entrance31. With "in," contribute32. Airport building33. Move backwards34. Unclear mixup

Down1. Beer plant2. "Let me ___ your memory."3. Supervisory body4. It's a long story8. Amount of medicine9. Investments carry this

10. "I'll huff & I'll puff..."11. Vehicle for verse greetings12. A nurse may take yours13. Celebrating Thanksgiving, e.g.15. An airline's critical city17. Comedian's currency18. Sausages20. Run in different directions22. It's done on a runway24. Consider again28. Not a poser30. Dieter's dread

12. A nurse may take yours 13. Celebrating Thanksgiving, e.g. 15. An airline's critical city 17. Comedian's currency 18. Sausages

20. Run in different directions 22. It's done on a runway 24. Consider again 28. Not a poser 30. Dieter's dread

Documents

Pushing the Boundaries of Space · 31 invited conference presentations, and contributed to 166 other presentations. The research topics include under-standing the ring current, diffuse