Deep Space Communication Architecture Study. J. D. Baker 1 , N. E. Lay 1 , 1 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena CA 91109. Introduction: This abstract describes work per- formed for the NASA Solar System Exploration Pro- gram on a recent deep space communications architec- ture study for both in-flight and ground capabilities that could support small spacecraft on future planetary mis- sions. The study objective was to define a proposed standard communication for primary spacecraft that could work with any selected secondary spacecraft or ride-along vehicle. The study also addressed current communication architectures including various types of networks and capabilities compatible with the objec- tives of the study for both standalone direct-to-Earth and mother-daughter-ship mission architectures. The study also addressed navigation needs for both interplanetary and for proximity operations [1]. A written report de- scribes the recommended flight-to-ground and flight-to- flight architectures and equipment options for primary and secondary spacecraft. Figure 1. Cassini Spacecraft and Huygens Probe Approach: To perform the study, a team was orga- nized with representatives from the NASA Goddard Space Flight Center, the Ames Research Center, the Ap- plied Physics Lab and the Jet Propulsion Lab. Members with current and prior flight experience of both large and small flight missions were included and also repre- sentatives from the Deep Space Network. Driven by science downlink, a number of reference scenarios were defined and then evaluated. Scenarios were largely de- fined by range or rather distance from Earth and also by destination (eg. Moon, Mars). Each of the elements in the architecture was then defined starting with the cur- rent capabilities and constraints. Once agreed to, then options for the elements were also defined. The primary spacecraft capabilities were defined and captured and then the secondary vehicles were specified including a very small spacecraft with limited capabilities, like a CubeSat, and also a larger and more capable SmallSat in the 100 kg class. Both X, and Ka-band frequencies were included for Direct-to-Earth (DTE) and proximity communications. Historical examples including the Galileo Jupiter atmospheric probe and the Titan Huy- gens probe were examined for reference. Then analysis was done to assess data return capabilities of the various scenarios and element capabilities. DSN advanced tech- nologies for peak offload [5] were also included and other more speculative options including Deep Space Demand Access. Finally the study produced findings and suggestions for consideration by NASA. The Study: Returning science data from great dis- tances is no simple task. RF signal energy and conse- quently data return rate, drops as the square of the dis- tance. So for very large distances, a big antenna and/or RF high power amplifier is needed to achieve sufficient communication link closure with Earth ground stations. The Deep Space Network (DSN) has thirteen opera- tional ground stations in three locations (Canberra, Ma- drid, Goldstone) spread around the globe with both 34m and 70m dishes to make contact with spacecraft around the solar system. This study examined capabilities for current mis- sions for reference and historical examples where sec- ondary probes were used (eg Galilleo and Cassini). Var- ious planetary destinations were assessed for DTE ca- pabilities for SmallSats including the Moon, Mars, Ve- nus and Near Earth Asteroids (NEAs)[2]. SmallSats are typically less capable that primary missions due to lim- ited on-board power capabilities and consequently re- duced RF transmit power. The performance limitations were examined for a number of data rates and findings made that could make SmallSats able to provide mean- ingful science data return. Figure 2. SDST and Frontier Spacecraft Radios In order to define reference telecommunication pay- load capabilities, we considered available deep space and proximity radios used by larger missions including the Frontier radio, the Small Deep Space Transponder (SDST) and Electra and Electra-lite UHF Transceivers 2940.pdf 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)
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Deep Space Communication Architecture Study. J. D. Baker1 , N. E. Lay1, 1Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena CA 91109.
Introduction: This abstract describes work per-
formed for the NASA Solar System Exploration Pro-gram on a recent deep space communications architec-ture study for both in-flight and ground capabilities that could support small spacecraft on future planetary mis-sions. The study objective was to define a proposed standard communication for primary spacecraft that could work with any selected secondary spacecraft or ride-along vehicle. The study also addressed current communication architectures including various types of networks and capabilities compatible with the objec-tives of the study for both standalone direct-to-Earth and mother-daughter-ship mission architectures. The study also addressed navigation needs for both interplanetary and for proximity operations [1]. A written report de-scribes the recommended flight-to-ground and flight-to-flight architectures and equipment options for primary and secondary spacecraft.
Figure 1. Cassini Spacecraft and Huygens Probe Approach: To perform the study, a team was orga-
nized with representatives from the NASA Goddard Space Flight Center, the Ames Research Center, the Ap-plied Physics Lab and the Jet Propulsion Lab. Members with current and prior flight experience of both large and small flight missions were included and also repre-sentatives from the Deep Space Network. Driven by science downlink, a number of reference scenarios were defined and then evaluated. Scenarios were largely de-fined by range or rather distance from Earth and also by destination (eg. Moon, Mars). Each of the elements in the architecture was then defined starting with the cur-rent capabilities and constraints. Once agreed to, then options for the elements were also defined. The primary spacecraft capabilities were defined and captured and then the secondary vehicles were specified including a very small spacecraft with limited capabilities, like a CubeSat, and also a larger and more capable SmallSat
in the 100 kg class. Both X, and Ka-band frequencies were included for Direct-to-Earth (DTE) and proximity communications. Historical examples including the Galileo Jupiter atmospheric probe and the Titan Huy-gens probe were examined for reference. Then analysis was done to assess data return capabilities of the various scenarios and element capabilities. DSN advanced tech-nologies for peak offload [5] were also included and other more speculative options including Deep Space Demand Access. Finally the study produced findings and suggestions for consideration by NASA.
The Study: Returning science data from great dis-
tances is no simple task. RF signal energy and conse-quently data return rate, drops as the square of the dis-tance. So for very large distances, a big antenna and/or RF high power amplifier is needed to achieve sufficient communication link closure with Earth ground stations. The Deep Space Network (DSN) has thirteen opera-tional ground stations in three locations (Canberra, Ma-drid, Goldstone) spread around the globe with both 34m and 70m dishes to make contact with spacecraft around the solar system.
This study examined capabilities for current mis-sions for reference and historical examples where sec-ondary probes were used (eg Galilleo and Cassini). Var-ious planetary destinations were assessed for DTE ca-pabilities for SmallSats including the Moon, Mars, Ve-nus and Near Earth Asteroids (NEAs)[2]. SmallSats are typically less capable that primary missions due to lim-ited on-board power capabilities and consequently re-duced RF transmit power. The performance limitations were examined for a number of data rates and findings made that could make SmallSats able to provide mean-ingful science data return.
Figure 2. SDST and Frontier Spacecraft Radios In order to define reference telecommunication pay-
load capabilities, we considered available deep space and proximity radios used by larger missions including the Frontier radio, the Small Deep Space Transponder (SDST) and Electra and Electra-lite UHF Transceivers
2940.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)
Future radio capabilities were also considered including the Universal Space Transponder, and SmallSat radios including the Iris versio 2.1 radio and the Frontier lite radio [3].
Figure 3. Iris v2.1 radio and Universal Space Transponder A range of power amplifiers and antenna sizes were
also considered for both primary spacecraft and Small-Sats to achieve various data rates and science data return for both X-band and Ka-band frequencies. The empha-sis of theanalysis was on performance capabilities for SmallSats. A combined Ka-band transmitter with a low gain antenna was not considered since there is no real performance advantage. The performance range consid-ered was from 4-30W RF out for transmit power and from 0.5m to 1.5m for aperture size.
Figure 4. 0.5m Ka-band Deployable High Gain Antenna The DSN was also included as the principal ground
station for contact with deep space spacecraft. A number of prior and recent studies were included and reviewed to assess options for reducing the DSN load [4][5][6]. There are new DSN capabilities including Multiple Spacecraft per Aperture (MSPA) which can download from four spacecraft at the same time when they are all in the same half power beamwidth of the antenna as well as Opportunistic MSPA [7].
Summary: A new deep space communications ar-
chitecture will enable additional science to be per-formed for each mission at a marginal cost with Small-Sats. A secondary or ride-along vehicle will have the option of being carried by the same launch vehicle or spacecraft to perform additional planetary science.
Figure 5. Goldstone Complex Deep Space Antenna
References:
[1] J. Stuart, L. Wood, “SmallSat Navigation via the Deep Space Network: Lunar Transport”, 68th Interna-tional Astronautical Congress, Adelaide, Australia, 2017 (paper and presentation slides). [2] K-M. Cheung et al, “Next-Generation Ground Network Architecture for Communications and Tracking of Interplanetary Smallsats”, Interplanetary Network Progress Report, No. 42-202, August 15, 2015. [3] M. Kobayashi, “Cu-beSat Telecom System Needs for Deep Space Mis-sions”, 2017 Interplanetary Small Satellite Conference, May 1, 2017. [4] J. Gao, “Deep Space Demand Access Communications with Beacon”, JPL internal working charts, October 19, 2017. [5] JPL Deep Space Capacity Study Team, “Deep Space Capacity Study – Pass 2, Preliminary Report”, JPL study report for NASA SCaN PSE, April 2017. [6] D. Abraham, “2017 Future Deep Space Mission Trends & Implications”, JPL study report for NASA SCaN, 2017. [7] D. Abraham et al., "Opportunistic MSPA Demonstration #1: Final Re-port," IPN PR 42-200, pp. 1-27, February 15, 2015.
Acknowledgements: This work was performed us-ing NASA funding. We want to acknowledge and give our tanks to the team involved in this study. They in-cluded Matt Angert (APL), Mike Powers and Dave Is-rael (GSFC), Vanessa Kuroda (ARC), Damon Landau (JPL), Faramaz Davarian (JPL), Jay Gao (JPL), Dave Hansen (JPL), Alessandra Babuscia (JPL) and Wallace Tai (DSN).
2940.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)
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