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Alessandra Babuscia
Jet Propulsion Laboratory – California Institute of Technology
Part of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. © 2015 California Institute of Technology. Government sponsorship acknowledged. 1
FISO Telecon 5-‐6-‐2015
! Introduction and history of the project ! Inflatable antenna (version 1)
! Design ! Fabrication ! Tests
! Extension to the X-‐Band ! Scalability and comparison with other technologies
! Conclusion and future work 2
! An increasing number of universities, companies and space agencies are actively designing, developing, launching and operating CubeSats.
! CubeSats have mostly been used to perform research in Low Earth Orbit and most of
the COTS components available in the market have been designed to that purpose.
! A new technological trend is the development of technologies and strategies for potential interplanetary applications of small platforms (CubeSats/Satellites).
! One of the most interesting problems is how to allow small satellites to communicate from very far distance in the solar system.
! Current work in this area includes developments in antenna design (deployable [1], reflectarray [2], inflatables [3]), amplifiers and transceiver designs [4] [5] [6], coding [7], CDMA [8], multiple spacecraft per antenna [9] and collaborative communication [10].
! In this presentation, I will focus on inflatable antenna: an overview of the history of the project, design, fabrication, tests, extension to the X-‐Band and current status
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STS 77-‐1996
Could this model be adapted to CubeSat?
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Babuscia, Van de Loo, et al., 2012 A new design was needed 6
! Requirements: ! Size of the reflector: at least 1 m diameter ! Frequency: S Band (2.4 GHz) ! Volume: less than 1U ! Mass: less than 1 Kg ! Power (for deployment mechanism): less than 1 W ! Inflation: simple and “low risk for the main mission”
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! CubeSats are generally launched as auxiliary payloads on the launch vehicle
! A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.
! The pressure differential is dangerous, and it could cause accidents that could damage the primary spacecraft
! In addition, pressure vessels could occupy a big portion of the CubeSat volume
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! Sublimating powder is a chemical substance such that given a certain change of pressure, it sublimates from a solid to a gas state
! Few grams of benzoic acid can inflate an entire balloon
! The mechanism is completely passive: ! No pressure vessel on board ! Simple ! It takes less volume than other inflation mechanism
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Echo Balloon 1964
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! Inflatable volume with one side reflective, metalized Mylar (1), other side clear Mylar (2) with a patch antenna (3) at the focus.
! Stored in a volume (4) less than 1U in size.
! Antenna passively inflated with a small amount of a sublimating powder.
! 2 versions: conical and cylindrical to minimize deformation of the parabolic shape of the reflective section.
Concept design of the inflatable antenna.
Conical (left) and cylindrical (right) configurations of the antenna.
Radiation
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12 12 ~21 dB ~16 dB
! Parabolic shape made with four petal-‐shaped pieces of flat Mylar bonded at edges. ! Edges are bonded with epoxy designed specifically for hard-‐to-‐bond plastics.
Finished reflective Mylar parabolic side
Finished antenna with polycarbonate plate.
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! 4 possible folding techniques
Method Vol. con. (U)
Vol. cyl. (U)
1 0.32 0.5
2 0.28 0.52
3 0.32 0.5
4 0.28 0.52
Regardless of the method chosen, the antenna can be folded in less than 0.52U
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! The deployment mechanism consists of two plates ! The ejector plate ! The base plate.
! A compression spring is mounted onto each of the 4 rods.
! The ejector plate sits on top of the compression springs and slides along the length of the rods.
! Nylon wires to hold the ejector plate.
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• Cylindrical and conical
configurations are reached but the reflector is not perfectly parabolic.
• More pressure measurements need to be performed in the future.
! The antenna was tested for EM gain at the JPL anechoic chamber in may 2013.
! A specific test stand was designed at MIT to maintain the antenna in the desired aligned position.
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2.1 2.2 2.3 2.4 2.5 2.6 2.7-10
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-6
-4
-2
0
2
4
6
8
f (GHz)
Gai
n (d
B)
Patch antenna
• The gain is not the one previously measured on the same patch antenna (previously 6 dB, now 4dB at 2.4 GHz).
• Possible mishandling of the antenna by another team as well as interactions with the polycarbonate plate are possible causes for the mismatch.
• As a result, the new performance metric for the test is the delta-‐gain:
patchinflatable G−=Δ GGsimulated18
2.1 2.2 2.3 2.4 2.5 2.6 2.7-10
-5
0
5
10
15
f (GHz)
Gai
n (d
B)
Inflatable antenna test: conical configuration
Inflatable antenna gainDelta-gainPatch antenna gain
• At 2.4 GHz, the delta gain is ~8.9 dB which is 1.1 dB less than expected.
• The possible cause is leakage in the antenna due to the impossibility of filling the antenna with helium at the Mesa.
• An helium pump at the Mesa was later found and used for the cylindrical antenna, but not for the conical.
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2.1 2.2 2.3 2.4 2.5 2.6 2.7-10
-5
0
5
10
15
f (GHz)
Gai
n (d
B)
Inflatable antenna test: cylindrical configuration
Inflatable antenna gainDelta-gainPatch antenna gain
• The delta gain measured at 2.4 GHz is 6.48 dB, very different from the 15 dB expected.
• This result was surprising given that the cylindrical antenna was inflated with helium at the Mesa, so leakage was supposed to play a very minor role.
• The team believed that the issue was due to the addition of the polycarbonate plate. Hence simulations were made to verify this hypothesis. 20
Vacuum chamber test Anechoic chamber test Analysis and remodeling
CAD Model: No plate CAD Model: Plate added
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CAD Model: No plate CAD Model: Plate added
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CAD Model: No plate CAD Model: Plate added
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Corrections were introduced to take into account the attenuation caused by the polycarbonate plate. The delta gain metric is used to indicate the increase in gain with respect to the standard patch antenna (+ 6 dB)
Freq. (GHz)
Delta Gain (Conical) measured (dB) with plate correction
Delta Gain (Conical)with plate correction (dB)
Delta Gain (Cyl) measured (dB) with plate correction
Delta Gain (Cyl)with plate correction (dB)
2.35 8.84 9.7 15.31 15.4
2.4 8.97 10.2 15.48 15.5
2.45 8.58 9.5 14.73 14.2
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! A new version of the inflatable antenna was designed to operate at X-‐band.
! A new patch antenna and a new reflector were manufactured.
! A professional company was engaged into the manufacturing of the dish to reduce leakage issues.
! A new testing plate was designed to attach the patch to the reflector.
Parameter Value
Antenna size 9 x 9 cm Antenna conductive plate size 1.2 x 1.8 cm
Impedance 50 Ohm
Dielectric RT Duroid 5880 (perm=2.2)
Frequency 8.4 GHz
Peak gain 8 dBi
New inflatable antenna on testing stand Patch antenna parameters Test plate 26
The simulation was set up at X-‐Band with the new patch Gain at 8.4 GHz of 34.3 dB.
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! Initial tests at X-‐band did not yet achieve the desired gain ! As a result of the new CIF grant, a structural re-‐design will
focus on improving the antenna characteristics ! Developing an accurate pressure vs. shape profile ! Develop a system to maintain the antenna at the desired
pressure while at the anechoic chamber test facility. ! Improvement of the antenna feed to improve the
focalization of the beam. ! Membrane re-‐manufacturing. ! Control and system analysis for future spacecraft design. ! Sublimating powder inflation process studied at ASU
! Vacuum chamber experiments ! Sublimating powders comparison and selection ! Reliability analysis and study of rigidization techniques.
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! The feasibility for the different frequencies: ! S-‐Band (~10 cm wavelength) : very feasible, wrinkles in the order
of 1 cm or less can be tolerated, pointing is generally few degrees. ! X-‐Band (3-‐5 cm wavelength): feasible, wrinkles in the order of 3-‐5
mm, and pointing becomes more complex (~ 1 deg), although achievable with more refined COTS sensors and actuators.
! Ka-‐Band (less than 1cm wavelength): very hard (tolerance is 1 mm or less) . Additionally, pointing becomes more complex and may require customized hardware and algorithms.
! For size, the inflatable antenna can be easily scaled up to larger sizes
Diameter (m)
Mass (Kg) Value (U)
1 0.4 0.4 2 1.4 1.4 4 5.1 5.1 8 20.5 20.5 29
! X-‐Band antenna concepts in development are projected to achieve gains ~ 30 dBi, although some of them have less stowing efficiency than the inflatable and they are not easily scalable to higher gain ! Reflectarray -‐ ISARA type
( 3 foldable 20 x 30 cm panels) ! Folding rib reflector based on Aeneas design
(0.5 m for 1.5 U volume)
! Miniaturized astromesh reflector (1 m for 3 U volume)
! The advancement of the inflatable antenna is given by:
! Stowing efficiency: 20:1 ! Low mass: 0.5 Kg for a 1m dish including canister
! Scalability to higher gains ! Simplicity of inflation: no pressure vessels,
no tank required
! One of the biggest challenges is the achievement of the desired efficiency, mostly as a result of the
irregularities of the surface. Initial tests performed at X-‐Band reveals that these irregularities can scatter the gain in multiple directions, hence reducing the gain in the desired direction.
Reflector diameter (m)
Volume (U) Gain (dBi) at X-‐Band
1 0.5 34
1.5 1 37
2 1 .4 40
Antenna Type
Reflector diameter (m)
Volume (U)
Stowing Efficiency
Folding Rib 0.5 m 1.5 5:1
Miniaturized Astromesh 1.0 m 3 10:1
Inflatable 1.0 m 0.5 20:1
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! An overview of the inflatable antenna project was presented.
! The initial design and test at S-‐band were presented.
! The extension to the X-‐band was discussed. ! Future work includes: testing the new antenna in the anechoic chamber, work on control system and on the deployment and stowage structure.
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! The inflatable antenna team over the years: Mark Van de Loo (MIT), Benjamin Corbin (MIT), Rebecca Jensen-‐Clem (Caltech), Mary Knapp (MIT), Quantum Wei (MIT), Serena Pan (MIT), Thomas Choi (JPL), Miguel Lorenzo (JPL).
! Prof. Sara Seager, Prof. Paulo Lozano, Prof. David Miller and the Space
System Laboratory at the Massachusetts Institute of Technology.
! Swati Mohan, Kamal Oudrhiri, Neil Murphy and the Center for Academic Partnership at the Jet Propulsion Laboratory.
! Jeff Harrel, Robert Beckon, Joseph Vacchione and the antenna testing team at the Jet Propulsion Laboratory.
! Kar-‐Ming Cheung, Polly Estabrook, Fabrizio Pollara and the staff of Section 332 at the Jet Propulsion Laboratory.
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[1] J. Sauder, N. Chahat, M. Thompson, R. Hodges and Y. Rahmat-Samii, "Ultra-Compact Ka-Band Parabolic Deployable Antenna for CubeSats," in Proceedings of Interplanetary CubeSat Workshop, Pasadena, CA, 2014.
[2] R. Hodges, B. Shah, D. Muthulingham and T. Freeman, "ISARA: Mission Overview," in 27th Annual AIAA/USU Small Satellite Conference, Logan, Utah, 2013.
[3] A. Babuscia, B. Corbin, M. Knapp, R. Jensen-Clem, M. Van de Loo and S. Seager, "Inflatable antenna for CubeSats: Motivation for development and antenna design," Acta Astronautica, vol. 91, pp. 322-332, 2013.
[4] A. Chin and C. Clark, "Class F GaN power amplifiers for CubeSat communication links," in IEEE Aerospace Conference, Big Sky, MT, 2012.
[5] C. Duncan, "Iris for INSPIRE CubeSat Compatible, DSN Compatible Transponder," in 27th Annual AIAA/USU Small Satellite Conference, Logan, Utah, 2013.
[6] K. Lyanaugh, "Communication Challenges of Small Satellites for Interplanetary Applications," in Interplanetary Small satellite Conference, Pasadena, CA, 2014.
[7] T. Sielicki, OVERCOMING CUBESAT DOWNLINK LIMITS WITH VITAMIN: A NEW VARIABLE CODED MODULATION PROTOCOL, University of Alaska Fairbanks: MS Thesis, 2013.
[8] D. Divsalar, A. Babuscia and K. Cheung, "CDMA Communications Systems with Constant Envelope Modulation for CubeSats," in IEEE Aerospace Conference (submitted), Big Sky, Montana, 2015.
[9] D. Abraham and B. MacNeal, "Opportunistic MSPA: A Low Cost Downlink Alternative for Deep Space CubeSats," in Interplanetary Small Satellite Conference, Pasadena, CA, 2014.
[10] A. Babuscia, K. Cheung, D. Divsalar and C. Lee, "Development of cooperative communication techniques for a network of small satellites and CubeSats in Deep Space," in Proceedings of the 65th International Astronautical Congress, Toronto, Canada, 2014.
[11] A. Babuscia, M. Van de Loo, M. Knapp, R. Jensen-Celm and S. Seager, "Inflatable Antenna for CubeSat: Motivation for Development and Initial Trade Study," in iCubeSat, MIT, Cambridge, 2012.
[12] A. Babuscia, M. Van de Loo, Q. J. Wei, S. Pan, S. Mohan and S. Seager, "Inflatable Antenna for CubeSat: Fabrication, Deployment and Results of Experimental Tests," in IEEE Aerospace Conference, Big Sky, Montana, 2014.
[13] A. Babuscia, M. McCormack, M. Munoz, S. Parra and D. Miller, "MIT Castor Satellite: Design, Implementation and Testing of the Communication System," Acta Astronautica, vol. 81, pp. 111-121, 2012.
[14] A. Babuscia, T. Choi and K. Cheung, "Inflatable antenna for CubeSat: Extension of the previously developed S-Band design to the X-Band," In preparation for Acta Astronautica, 2014.
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