NASA Space Communication and Navigation Program Next ... · NASA Space Communication and Navigation Program Next Generation Space Relay Architecture Concept Study . Architecture Background

NASA Space Communication and Navigation Program Next Generation Space Relay Architecture Concept Study

Architecture Background Information January 2016

NASA National Aeronautics and Space Administration

Space Communication and Navigation Program

Title: Space Relay Architecture Background Information Solicitation No.: NNC16ZLC002L Revision: 1 Effective Date: 01/15/2016 Page 2 of 22

DOCUMENT HISTORY LOG Status (Preliminary/ Baseline/ Revision/ Canceled)

Document Revision

Effective Date Description

Release 1.0 01/15/2016



TABLE OF CONTENTS 1 Scope ...................................................................................................................................... 4 2 Introduction ............................................................................................................................ 5

2.1 Planetary Networks ....................................................................................................... 5 2.1.1 Earth Network ................................................................................................... 5 2.1.2 Mars Network ................................................................................................... 6 2.1.3 Lunar Network .................................................................................................. 6

3 Architecture Provided User Mission Services ........................................................................ 9 3.1 SCaN Network Services ............................................................................................... 9

3.1.1 Communication ................................................................................................. 9 3.1.2 Navigation ....................................................................................................... 10 3.1.3 Space Internetworking .................................................................................... 10 3.1.4 Radio science .................................................................................................. 10

3.2 Proposed New SCaN Services .................................................................................... 10 3.2.1 User Initiated Schedule Service ...................................................................... 10 3.2.2 Time ................................................................................................................ 10 3.2.3 Space Internetworking .................................................................................... 11 3.2.4 Broadcast Service............................................................................................ 11

3.3 SCaN Services Transition Summary .......................................................................... 12 4 Concepts of Operations for Service Scheduling ................................................................... 13 5 Sample Architecture ............................................................................................................. 16

5.1 Near Earth Architecture .............................................................................................. 16 5.2 Deep Space Architecture............................................................................................. 18

5.2.1 Mars Network ................................................................................................. 18 5.2.2 Lunar Network ................................................................................................ 19

6 Acronyms and Glossary ....................................................................................................... 21

LIST OF FIGURES Figure 1: Near Earth, Mars, and Lunar Network Concept .............................................................. 7 Figure 2. Planetary Networks Concept ........................................................................................... 8 Figure 3: 2040 SCaN Network Service Provision ........................................................................ 13 Figure 4: Simplified ConOps for UIS in the Near Earth Domain................................................. 15 Figure 5. Near Earth C&N Architecture ....................................................................................... 17 Figure 6. Deep Space C&N Architecture – Mars Network .......................................................... 20 Figure 7. Planetary C&N Architecture – Lunar Network ............................................................. 20

LIST OF TABLES Table 1. Next Generation Architecture – Services ....................................................................... 12



1 SCOPE

The NASA Space Communications and Navigation (SCaN) Office was formed in 2007 to unify the management of the NASA’s disparate networks to more effectively meet the needs of and enable NASA’s flight missions by providing responsive communications and navigation (C&N) capabilities and services. As enabling technologies and the needs of future missions change, SCaN must continuously evolve to meet effectively the challenge in accordance with NASA Policy Directive (NPD) 8074.1, Management and Utilization of NASA's Space Communication and Navigation Infrastructure.1

The purpose of this Next Generation Architecture Background Information document (hereafter the “Background”) is to provide high level information on one of the potential Next Generation Architecture (Next Gen) concepts emerging from previous NASA studies to evolve the space communications and tracking networks and mission capabilities. The report illustrates concepts for the architecture when many, if not all, of the new services, capabilities, and assets will be deployed and operated in space and terrestrially. These capabilities are expected to be developed and deployed over time.

Recognizing that the scope of the NASA Next Generation Space Architecture Concept Study is focused on the near Earth and deep space relays, it is envisioned that the Background will provide some broader context, at least in the spatial domain, for the relay architecture. Offerors are cautioned that this document does not contain any requirements, should not be considered as direction, and no Next Gen Architecture decisions have been made.

Offerors are expected to use the information in this paper as an input to their studies. Offerors results may confirm, modify, or contradict information in this paper.

1 NPD 8074.1 states in part: “1. POLICY

a. It is NASA's policy to maintain a unified process for the development and utilization of Agency space communications and navigation (C&N) infrastructure and for the enhancement of this infrastructure to enable new capabilities for the future. NASA's space C&N infrastructure includes the following:

(1) The ground and space-based facilities and assets of what are presently known as the Near Earth Network (NEN), the Deep Space Network (DSN), and the Space Network (SN).

(2) Communications networks around all heavenly bodies beyond Earth, including the Moon, Mars, or other planets, providing support to surface as well as orbital user missions.”



2 INTRODUCTION

2.1 Planetary Networks

Envision the solar system divided into: (a) the Near Earth domain from Earth’s surface to 2 million kilometers (M km); and (b) the Deep Space domain from 2M km to the edge of the solar system. Regions of the solar system that have sufficient spacecraft and rich enough connectivity through space-to-space and space-to-ground links will have planetary networks. The planetary networks will grow into three segments as they emerge:

1) a Ground Segment on Earth providing network control and ground stations; 2) a planetary Space Segment with one or more orbiting spacecraft providing data relay and

tracking/positioning capabilities; and 3) a planetary Surface Segment consisting of communication terminals such as Wide Area

Networks (WAN) or Local Area Networks (LAN) on the planetary surface. The orbiting relay spacecraft and surface communication terminals multiplex and demultiplex to provide services to many orbiting user spacecraft and surface systems such as rovers, habitats, landing and ascent vehicles, Extra Vehicular Activity (EVA) crew, and In-situ Resource Utilization (ISRU) systems.

The future Space Communication Networks (SCN) needed to provide services across the solar system will be operated by an international set of organizations (government and commercial) that voluntarily cooperate to provide an integrated network.

2.1.1 Earth Network The first and largest planetary network is the Earth Network (EN), which will consist of a set of networks each of which may have a Ground Segment with ground stations and network control centers and a Space Segment for relay and tracking spacecraft in Earth orbit. In addition, the network will include an external system for position determination such as the Global Positioning System (GPS). Although GPS is external to NASA, is considered here as another part of the EN provided by the US Government (USG) providing time and position services to NASA missions.

Today’s EN consists of the Near Earth Network (NEN), a collection of ground stations (both NASA and commercially owned and operated) located around the world providing services to user mission spacecraft typically in Earth orbits and the Space Network, a constellation of geosynchronous satellites providing data and navigation services to user mission spacecraft in Earth or lunar orbit. In addition, ground stations (i.e. DSN) on Earth provide destinations for planetary networks such as at Mars or individual planetary satellites. NASA’s portion of the EN Ground Segment will evolve from the current SN, NEN, and DSN into NASA’s SCN Control and Ground Segment (SCGS). NASA’s EN Space Segment will evolve from the current Tracking and Data Relay Satellite System (TDRSS) into the future Earth Relay (ER) capability. NASA’s ER may operate in Geosynchronous Earth Orbit (GEO) as well as other orbits and may include dedicated relay and tracking satellites, hosted payloads for relay and/or tracking functions, Commercial Service Providers (CSP), and other options. The EN provides service in the near Earth domain (out to 2 M km). The SCGS will operate the future ER segment.



2.1.2 Mars Network Today, the Mars Network (MN) includes three NASA spacecraft with relay capabilities and ESA’s Mars Express. Over time, NASA will evolve its Mars capability from relay packages embedded in science spacecraft towards small dedicated relay satellites to meet increasing science needs in the 2020’s and new human exploration needs in the 2030’s. The Mars network will include nodes on Human Exploration elements such as orbiting habitats and transit vehicles and, for example, communications between any two points will only require proximity links, e.g., between relay(s) in Aero-Synchronous Orbit (ASO), spacecraft in Low Mars Orbit (LMO), and surface systems, thus, avoiding trunk links to Earth involving long delays. Proximity links not only require less power; they also need less stringent pointing and tracking and have higher link availability. In the far future, additional planets and moons (e.g., Saturn or Europa) could acquire planetary networks demonstrating the scalability of this concept.

2.1.3 Lunar Network The Lunar Network (LN) may emerge in the 2020’s to provide service to science and robotic exploration missions especially to polar and far-side locations that are not serviced or partially serviced by Direct From/To Earth (DFE/DTE) links. Lunar and Mars Networks require trunk links to Earth for connectivity and network management. NASA’s Lunar network will be controlled by the NSCGS on Earth. The NEN and DSN will become part of the NSCGS which will be used to communicate with all other NASA planetary spacecraft.

A LN will have orbiting Lunar Relays (LR), Lunar Positioning Capability (LPC), and surface Lunar Terminals (LT) that may be provided by NASA, commercial or international partners. The Next Generation Architecture will consist of multiple planetary networks, particularly the near Earth network, the Mars network and the Lunar network.

The LN is shown in these studies as a potential third planetary network beyond Earth and Mars and is not a key element of the Next Generation Architecture Study.

As shown in Figure 1, these planetary networks will consists of a number of satellite links (e.g. trunk, proximity), and various nodes (e.g. Early relay, Mars relay, Lunar relay, science orbiters). The respective network relays, and links depicted in the figure are for illustration only and do not necessarily represent the future architecture as drawn. The Next Gen Architecture study will help define the specific relay capability of each planetary network. These planetary networks will utilize standard protocols and services, and commonality of hardware and software, as modular off-the-shelf components to dramatically reduce acquisition and operating costs for missions and networks. Within the Mars planetary system, for example, communications between any two points will only require proximity links, e.g., between relay(s) in Aero-Synchronous Orbit (ASO), spacecraft in Low Mars Orbit (LMO), and surface systems, thus, avoiding trunk links to Earth involving long delays. Proximity links not only require less power; they also need less stringent pointing and tracking and have higher link availability. Low power proximity links hold true even for the Moon providing a major benefit for small satellites such as CubeSats. The low latency between network nodes within a planetary network also enable telerobotics, e.g., astronauts in Mars orbit could control Mars surface systems in real-time via the Mars Relay. In the far future, additional planets and moons (e.g., Saturn or Europa) could acquire planetary networks demonstrating the scalability of this concept.



Figure 2 shows the set of Space Communication Networks (SCN) needed to serve the solar system being operated by an international set of organizations that voluntarily cooperate to provide their infrastructure that interoperate. The evolution of NASA’s SCN is shown from 2015 (green) to 2040 (orange). The Initial Operational Capability (IOC) of the SCGS and ER will occur in ~2025 driven by the need to replace the capacity of TDRSS as its satellites are retired. Today’s networks gradually become the legacy architecture during the transition towards the future architecture. That legacy architecture remains in the picture because those spacecraft and ground stations will continue to provide service as long as they can be kept operational and as long as they have missions to support. Some legacy architecture assets such as antennas and TDRS satellites are expected to remain operational until 2040 and beyond.

Besides government networks, the EN may contain commercial, academic, and international systems that meet the requirements for interoperability. Examples may include the Swedish Space Corporation’s PrioraNet, Johns Hopkins University Applied Physics Lab’s (JHU APL) Satellite Communications Facility, and the European Space Agency’s (ESA) tracking station network (ESTRACK).

The GPS, although external to NASA, is considered here as another part of the EN provided by the US Government (USG) providing time and position services to NASA missions. In addition to GPS, GNSS are included such as the European Galileo, Japanese Quasi-Zenith Satellite System (QZSS), and Russian GLObal NAvigation Satellite System (GLONASS).

Figure 1: Near Earth, Mars, and Lunar Network Concept



Figure 2. Planetary Networks Concept

Figure 2 captures the networks that NASA operates including contracted CSPs but also depicts existing and potential networks operated by international space agencies, academic institutions, and CSPs offering independent service. The open architecture of the SSI enables independently operated networks to collaborate voluntarily to provide cross support. Over the next 25 years, it is anticipated that C&N capabilities pioneered by international space agencies will be augmented by commercial capabilities.



3 ARCHITECTURE PROVIDED USER MISSION SERVICES

The next generation architecture will be seen from the mission perspective to be a standard set of services and interfaces available from a variety of provider access nodes. Similar to the terrestrial mobile networks, system complexity will be hidden “inside the box” and the specific implementation done by the provider will not be seen by the mission. This will allow the provider to evolve the implementation as technology and funding allow. As the implementation evolves, the mission may see increased availability, new or enhanced services, new or enhanced interfaces, and/or reduced operations costs and complexity.

The end-state architecture will provide the future missions with enabling services that minimize burden and constraints placed upon the mission. In the near Earth environment, C&N services will be available on demand or, in the case of high rate and critical services, by schedule. Recognizing the trend towards increasing system autonomy, the scheduled services may be requested autonomously by mission platforms or MOCs and may become available within seconds or minutes of a request.

3.1 SCaN Network Services

The SCaN Program offers a range of world class space communications and navigation services and capabilities to enable the next generation of NASA’s science and exploration missions and global collaborations. These services allow missions to share the costs of critical, space infrastructure and eliminate individual and costly mission facilities providing a cost effective, national resource for space exploration.

The capabilities provided by the NASA space infrastructure adjust, and are responsive to the changing needs of science missions and plans for future human exploration of the solar system. A Service is defined as “…a self-contained set of functions with standard, well-defined interfaces: a Service is specified by its functions and interfaces. Services are delivered via Service instances, which are a specific Service performed over a specified time period.” Reference: Space Communications and Navigation (SCaN) Network Service Catalog, Phase 2, Rev.2.

3.1.1 Communication Communication services move user mission data through and among SCaN infrastructure elements. Communication services cover a wide range of functions and capabilities depending upon the mission need. Examples include;

• Data to and from user satellites through relay satellite to SCaN ground stations on Earth • Data to and from user satellites directly with SCaN ground stations on Earth • Data from one user platform to another through a relay satellite (e.g. one Mars rover to

another through a Mars relay satellite) • Data moved among a planetary wireless network among rovers and habitats.



3.1.2 Navigation Next Gen navigation services will provide improved availability and accuracy by expanding and enhancing the services available today. Metric tracking data will be provided on any microwave or optical carrier that carries data. Observations will be formed on space-to-space, space-to-ground, and ground-to-space physical links and then delivered to consumers of metric tracking data according to new protocols. Optimetrics will provide order of magnitude improvements in ranging, Doppler, and pointing (angular) observation accuracy. Non-coherent observation types, specifically one-way forward ranging (new service provided by SCaN) and Doppler, will facilitate autonomous navigation on-board the mission platform. In areas of high mission concentration, a navigation beacon may be provided as the basis of a stand-alone service. Navigation observables will be tied to a common time scale and will be compatible with GNSS in the near Earth domain.

3.1.3 Space Internetworking While IP-based networking is currently being introduced for service within single networks, future service will expand to full establishment of NASA’s network with IP-based and DTN-based interoperability among space and terrestrial networks.

3.1.4 Radio science Radio science services provide users a unique measurement capability of the integrated network infrastructure (e.g. ground stations). Services may include very long baseline interferometry, radar services, and forward/return RF carrier signal transmission/reception.

3.2 Proposed New SCaN Services

3.2.1 User Initiated Schedule Service User Initiated Scheduling is a new service under consideration for the future network. User initiated service allows mission spacecraft (or MOC) to directly initiate request for asset allocation through an automated system of resource assignments.

In the future, one could envision spacecraft requesting not only a time window of service, but also request custom bandwidths to increase network and system efficiency. The cost of developing and implementing an automated resource allocation system compared to other scheduling mechanisms should be considered.

3.2.2 Time Time transfer services will enhance operations, complement navigation services, and enable new science. Precise time synchronization of the network and missions allows for the application of new multiple access techniques and thereby increase the number of simultaneous missions supported by the network. Transition to one-way range and Doppler tracking data also requires synchronization but will allow for new processing/routing relay satellite designs in place of bent pipe relays. A reduction in timing errors is necessary to translate the accuracy of optometric observations to accuracy in orbit determination. Radio and optical science applications will benefit from an increase in time and frequency precision of the network and the mission.



3.2.3 Space Internetworking Space Internetworking services under consideration as a new service in the future network have the potential to “…significantly increase the operational flexibility and robustness of missions, as well as enabling mission classes otherwise untenable. In addition, networked communications offers additional redundancy and resiliency to failure of an individual asset or to conditions that do not permit line-of-sight communication with Earth. It is clear that the use of relay communications, and networks built upon the relayed, routed data concept offers many advantages to traditional point-to-point communications. This comes at a cost, however, in that the assets providing the relay service must also themselves be deployed and operated”

Internetworks will handle the handover of data from one satellite to another or from one ground station to another, ensuring continuous data flow from spacecraft to mission center. Responsibility for data is shared among the participating elements providing for retransmissions, prioritizations, buffering, and automatic rerouting based on failures.

Network layer services will allow missions to have a network layer interfaces (e.g. IP packet or DTN bundle) which will deliver data to its destination by the SCaN Network. These services will eliminate the need for mission-unique gateways and protocol conversions.

Reference: Solar System Internetwork (SSI) Architecture, Consultative Committee for Space Data Standards, Green Book, July 2014.

3.2.4 Broadcast Service Broadcast services are a new service under consideration for the future network. Broadcast services provide both general and specific state and network (e.g. management) information to user spacecraft, transmitted simultaneously to all users. A variety of mission aids such as network information and navigation aids will be available to all SCaN missions without the need for scheduling. The Broadcast service may also include low data rate forward messages for ODS and user initiates scheduled service.

Features of this service would be to share timing and GPS correction information, space weather, network and service assignments, network status, and other operational advancements.



4 CONCEPTS OF OPERATIONS FOR SERVICE SCHEDULING

The SCaN Network will provide services in a manner that combines the best attributes of the SCaN service provisioning of today, along with best attributes of commercial telecomm service provisioning. The future SCaN Network will be one part of a global space communications network to support space missions. The SCaN Network will lead the introduction of certain features, but will strive to ensure compatibility with other networks. The SCaN Network will provide common interfaces that are also compatible with other agencies and commercial service providers. This will allow for increased interoperability, providing flexibility in service for missions of many agencies.

Figure 3 shows a schematic of how the mission’s platforms and ground systems will interact with the SCaN ground segment (SCGS) and the space segments of the Earth Network, Lunar Network, and Mars Network when scheduling and receiving service. The general ConOps will be the same in all three space segments, but the specific details may vary to suit the specific needs in each region. The LN may be provided by international partners to suit international agency’s needs as well as NASA’s, but will provide similar functionality as the other space networks. In the figure, Comm & Metric service refers to Forward Data Delivery Service, Return Data Delivery Service, Internetworking Service and Metric Services.

SCaN and its service interfaces will become highly automated in service provisioning, greatly reducing the labor required for both SCaN and the missions. For instance, link connections will become adaptive (e.g. using cognitive techniques), changing parameters such as coding, data rate, etc. as link conditions require for optimal throughput. The system will provide three methods for scheduling and providing services to the missions: On-Demand Service (ODS); Pre-Planned Service (PPS); and User Initiated Service (UIS). PPS will be highly automated for scheduling, while ODS and UIS will by necessity be completely automated.

Figure 3: 2040 SCaN Network Service Provision



ODS provides low date rate forward and return services via relay for TT&C and other uses. It will be available in regions serviced by the Earth, Lunar, and Mars Networks. Service will be initiated by the mission platform or ground system, and the SCaN Network will set up the service nearly instantaneously. Sufficient capacity will be available to provide very high availability according to the QoS agreed to with the missions. The implementations of these services are expected to be optimized for availability, so the necessary trades are expected to lead to lower performance such as data rates as compared to other parts of the network.

PPS will be an evolution of the current method of scheduling, using an automated algorithm developed in conjunction with SMD, HEOMD and others using inputs such as mission priority, data criticality, etc. to develop the schedule for comm, metric, and science services. PPS is initiated from the mission ground system via a request to the SCaN Service Request System (SRS). PPS will allow for scheduling of services in advance of the service where appropriate. It is intended for use in areas where UIS is not available such as in deep space DTE links, to cover known service needs such as critical events, and when it best fits the mission needs. It also covers other services such as Navigation, Science, and Calibration Services that do not require direct interaction with the mission platform.

UIS is a new scheduling method that allows the mission to schedule service within a short scheduling window from both the mission platform and ground system. The UIS request can come from either the mission platform to the SCaN space segments or from the mission ground system to the SCGS depending on the mission need. UIS can provide service through any SCaN Network assets, including relays and ground stations. The UIS request will include information on the service required such as data volume, latency requirements, radio parameters, etc. that allow SCaN to provision the service, along with positional information such as ephemerides in order to establish the link connection. The SCaN Network will have enough capacity to support the UIS requests according to a QoS agreed to during the mission planning. Only high priority UIS requests such as emergencies may be able to override existing service schedules.

In UIS, the mission contacts SCaN to request service within seconds to hours scheduling window. The mission platform can directly contact SCaN via SCaN’s Space Segments utilizing a UIS protocol over an available link. The receiving satellite node determines whether it can provide the service, or must forward the request to the central SRS. If the receiving node can provide the service, it will inform the SRS that the node’s operating schedule has changed and initiate the service with the mission platform. If the receiving node does not have the available capacity, performance, authority to decide to provide the service, etc., the request will be forwarded to the SRS to determine the appropriate node to provide the service. The receiving node will forward the appropriate service schedule and parameters to the mission platform for service execution at the appropriate providing node. UIS requests can also come from the mission ground system to the SCGS.



5 SAMPLE ARCHITECTURE

The sample architecture provided below is intended as an abstract representation of various studies conducted over the past few years. The types of entities and their characteristics are defined but specific details about those entities (instantiation) such as quantity, physical location, year of operation, and performance parameters are not defined. For example, a figure may depict a set of three relays providing global coverage of a planet. This does not mean that three relays are required, since the initial configuration may consist of a single relay, nor does it limit the final configuration to three relays, since added relays may be necessary to meet capacity requirements.

5.1 Near Earth Architecture

As shown in Figure 5, at the end state the near Earth architecture is comprised of provider nodes, located at diverse nodal points in space and terrestrially. For terrestrial through GEO coverage, Nodal points in space can be distributed in at least three GEO locations with field-of-view to ensure 24x7 network access; though additional nodal points can provide overlapping coverage areas, increased network bandwidth, and increased network availability. Terrestrial nodal points can be distributed to provide coverage above LEO to enable 24x7-network access and to provide services to LEO missions in view without requiring the burdens associated with LEO to GEO links. Commonality of interfaces and services at provider nodes will allow support of missions as they transition past GEO. In the region between GEO and the Near Earth spectrum boundary at 2 million km, ground assets with required link performance with the possible addition of extended field of view space relay assets will provide the common support. Missions will also be able to receive support through commercial and international providers using the same standards and interfaces, following established peering relationships between SCaN and the other providers. Missions will be able to focus only on how they connect to the network and not be concerned with how their data is delivered end-to-end.



Figure 5. Near Earth C&N Architecture Services will be provided to mission platforms by optical and RF communications links as required to meet aggregate mission needs. The relay space-to-ground links, referred to as trunk lines, between space relays and ground stations will be implemented with a combination of RF and optical links as required to provide the necessary data bandwidth and QoS. Services can be provided to missions using near Earth spectrum bands up to 2 million km from Earth including cislunar and Sun-Earth L1 and L2 orbits.

For those services that are not available on demand, missions have the ability to request services in an autonomous manner with a guaranteed level of network response. This capability is known as UIS. There are three methods for obtaining service: ODS, PPS, or UIS.

To ensure commoditization between the interoperating networks, technology transfer programs from NASA will drive capability and innovation for the network and missions alike. The development of technologies such as low mass and power optical communications terminals, space-qualified network routers, chip-scale atomic clocks, and common network management tools is needed to create an efficient and robust interoperable network. These technologies should be worked in conjunction with US industry to ensure alignment to appropriate standards. Interoperable standards will be developed and available internationally to ensure the possibility of federated services from other providers.



5.2 Deep Space Architecture

The deep space C&N architecture has the following key characteristics:

1) Service paradigm: It is a service architecture that has been advanced to providing full-fledged, end-to-end network layer services and application layer services. Moreover, the architecture enables the provision of some internet-like SOA services by the SCaN network and user missions.

2) Mars Network: It includes a Mars Network comprised of multiple dedicated relay orbiters and relay payloads hosted by NASA’s science orbiters.

3) Optical communications: It provides global coverage via optical communication links available to all deep space missions.

4) Lunar Network: It includes a Lunar Network featuring relay orbiters in a high lunar orbit providing coverage for orbiters in low lunar orbit, landed vehicles at Lunar South or North Poles, and landers on the lunar far side.

5) Earth-based ground stations: Large aperture assets, e.g., an array of 34m stations and optical telescopes, will be deployed and upgraded to meet the functional and performance needs of deep space missions.

Services paradigm: As shown in Table 1, the service paradigm of the end-state deep space architecture differs drastically from that of the present SCaN network architecture:

• Network layer service: In compliance with CCSDS DTN standards, all network assets (relays and ground stations) in the deep space C&N architecture operate as DTN nodes to provide the layer-3 service. While space link layer services, previously existing by directionality as forward and return services, are still available, they are “exposed” to user missions only for certain anomalous events.

• Optimetric data service: This service provides observables, as a new “tracking” data type, derived from the measurements that are acquired over the optical link.

• Celeslocation service: This service determines the location of a mission lander, rover, or fixed system on a celestial body (expandable to include airborne systems on Mars). The Lunar and Mars Positioning Capabilities perform a similar function to GPS although they may have a different architecture with fewer assets requiring more time to integrate position signals.

• SOA services: At the application layer, certain internet-like SOA services, e.g., look-up, directory, caching, storage, messaging, alarms/alerts (e.g., space weather, other cosmic events, and spacecraft emergencies), become available.

5.2.1 Mars Network Figure 6 depicts the Mars Network in the end state architecture. The Mars Network can be characterized as follows:

• It may be a full-fledged network comprised of multiple dedicated relay orbiters in areosynchronous orbit and/or relay payloads on NASA’s science orbiters. The Mars Network, therefore, is capable of scaling up to provide continuous coverage to human exploration and science activities on Mars.



• The Mars Network provides near-continuous trunk line availability, thus minimizing end-to-end forward/return data latency.

• Each relay orbiter communicates with Earth-based ground stations via a trunk line using RF (Ka- and X-bands) and optical links.

• Each relay orbiter is capable of supporting the return trunk line at a maximum data rate of ~150 mega-bits per second (Mbps) (in Ka-band) and ~300 Mbps (in optical); and 50 Mbps for the forward trunk line.

• Each relay orbiter communicates with the mission orbiters (science or exploration spacecraft) via cross-links, and with surface vehicles (habitats, communications stations, landers, and rovers) via proximity links. The maximum data rate of these local links for each mission is 50 Mbps (Ka or optical).

• Each relay orbiter, functioning as a DTN node, provides full network-layer services, plus on-demand, simultaneous/concurrent access by surface vehicles via proximity links and to mission orbiters via cross-links.

Optical communications are incorporated into the deep space C&N architecture are the following network assets:

• The deep space optical communications terminal deployed on mission spacecraft and all relay orbiters (including science relay orbiters).

• Three deep space optical ground telescopes providing global coverage via optical communication links to all deep space missions. Each telescope along with the optical communications terminal can achieve ~300 Mbps data rate.

5.2.2 Lunar Network Figure 7 depicts the LN in the end state architecture. The Lunar Network can be characterized as follows:

• It is a network comprised of a few science relay orbiters and the relay payload on each of NASA’s CubeSat/SmallSat orbiters and surface vehicles, i.e., lander, rover, seismic stations, and radio astronomy stations. The LN, therefore, at this stage provides focused utility, i.e., supporting the exploration at the lunar poles and far side of the moon where visibility by Earth stations is not possible. Nevertheless, the lunar relay also provides opportunistic support to science orbiters operated by international partner agencies.

• The Lunar Relay provides continuous trunk line availability to its user missions (given the continuous coverage from the Earth stations).

• Each relay orbiter communicates with Earth stations via a trunk line of RF link (Ka- and X-bands) and optical link.

• The relay orbiter, functioning as a DTN node, provides network-layer service, plus on-demand, simultaneous/concurrent access by surface vehicles via proximity links and to mission orbiters via cross links.

• The relay payload resident on each of NASA’s CubeSat/SmallSat orbiters and/or surface vehicles includes low-power, low-mass, small-volume SDRs.



Figure 6. Deep Space C&N Architecture – Mars Network

Figure 7. Planetary C&N Architecture – Lunar Network



6 ACRONYMS AND GLOSSARY

ASO Areosynchronous Orbit C&N Communications and Navigation CCSDS Consultative Committee on Data Space Standards CLTU Communication Link Transmission Unit CSP Commercial Service Provider DSN Deep Space Network DFE/DTE Direct From/To Earth DTN Delay/Disruption Tolerant Networking EN Earth Network ER Earth Relay ESA European Space Agency EVA Extra Vehicular Activity Gbps Billion bits per second GEO Geosynchronous Earth Orbit GLONASS GLObal NAvigation Satellite System GNSS Global Navigation Satellite Systems GPS Global Positioning System IA International Agency InSight Interior Exploration using Seismic Investigations Geodesy and Heat Transport IP Internet Protocol LEO Low Earth Orbit LN Lunar Network LPC Lunar Positioning Capability LR Lunar Relay LT Lunar Terminal MA Multiple Access MAVEN Mars Atmosphere and Volatile EvolutioN Mbps Million bits per second MN Mars Network MOC Mission Operations Center MPC Mars Positioning Capability MRO Mars Reconnaissance Orbiter NASA National Aeronautics and Space Administration NEN Near Earth Network NPD NASA Policy Directive ODS On-Demand Service OGA Other Government Agencies PAT Pointing, Acquisition, and Tracking PPS Pre-Planned Service QoS Quality of Service QZSS Quasi-Zenith Satellite System RF Radio Frequency SA Single Access SCaN Space Communications and Navigation SCGS SCN Control and Ground Segment SCN Space Communication Networks SN Space Network SNR Signal to Noise Ratio SOA Service-Oriented Architecture SRS Service Request System



SSI Solar System Internet TDRSS Tracking and Data Relay Satellite System TT&C Telemetry, Tracking and Command UHF Ultra High Frequency band UIS User Initiated Service USG US Government VLBI Very Long Baseline Interferometry W-LAN Wireless Local Area Network

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NASA Space Communication and Navigation Program Next ... · NASA Space Communication and Navigation Program Next Generation Space Relay Architecture Concept Study . Architecture Background