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 ! Inatable 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], reectarray [2], inatables [3]), ampliers 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 inatable 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 reector: 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 ! Ination: 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 dierent from the ambient pressure.

! The pressure dierential 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 inate an entire balloon

! The mechanism is completely passive: ! No pressure vessel on board ! Simple ! It takes less volume than other ination mechanism

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Echo Balloon 1964

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! Inatable volume with one side reective, 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 inated with a small amount of a sublimating powder.

! 2 versions: conical and cylindrical to minimize deformation of the parabolic shape of the reective section.

Concept design of the inatable antenna.

Conical (left) and cylindrical (right) congurations of the antenna.

Radiation

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12 12 ~21 dB ~16 dB

! Parabolic shape made with four petal-shaped pieces of at Mylar bonded at edges. ! Edges are bonded with epoxy designed specically for hard-to-bond plastics.

Finished reective 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

congurations are reached but the reector 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 specic 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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f (GHz)

Gain

(dB)

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= GGsimulated18

2.1 2.2 2.3 2.4 2.5 2.6 2.7-10

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f (GHz)

Gain

(dB)

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 lling 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

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f (GHz)

Gain

(dB)

Inflatable antenna test: cylindrical configuration

Inflatable antenna gainDelta-gainPatch antenna gain

The delta gain measured at 2.4 GHz is 6.48 dB, very dierent from the 15 dB expected.

This result was surprising given that the cylindrical antenna was inated 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 inatable antenna was designed to operate at X-band.

! A new patch antenna and a new reector 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 reector.

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 inatable 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 prole ! 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 ination 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 dierent 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 rened 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 inatable 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 eciency than the inatable and they are not easily scalable to higher gain ! Reectarray - ISARA type

( 3 foldable 20 x 30 cm panels) ! Folding rib reector based on Aeneas design

(0.5 m for 1.5 U volume)

! Miniaturized astromesh reector (1 m for 3 U volume)

! The advancement of the inatable antenna is given by:

! Stowing eciency: 20:1 ! Low mass: 0.5 Kg for a 1m dish including canister ! Scalability to higher gains ! Simplicity of ination: no pressure vessels,

no tank required

! One of the biggest challenges is the achievement of the desired eciency, 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.

Reector diameter (m)

Volume (U) Gain (dBi) at X-Band

1 0.5 34

1.5 1 37

2 1 .4 40

Antenna Type

Reector diameter (m)

Volume (U)

Stowing Eciency

Folding Rib 0.5 m 1.5 5:1

Miniaturized Astromesh 1.0 m 3 10:1

Inatable 1.0 m 0.5 20:1

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! An overview of the inatable 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 inatable 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.

! Je Harrel, Robert Beckon, Joseph Vacchione and the antenna testing team at the Jet Propulsion Laboratory.

! Kar-Ming Cheung, Polly Estabrook, Fabrizio Pollara and the sta 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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