IEEE Aerospace and Electronic Systems Magazine - July 2020 - 26

Feature Article:

DOI. No. 10.1109/MAES.2020.2975260

Improving Small Satellite Communications and
Tracking in Deep Space-A Review of the Existing
Systems and Technologies With Recommendations
for Improvement. Part II: Small Satellite Navigation,
Proximity Links, and Communications Link Science
Faramaz Davarian, Sami Asmar, John Baker, Jay Gao, Richard Hodges,
Damon Landau, Norman Lay, Leigh Torgerson, William Walsh, Jet Propulsion
Laboratory, California Institute of Technology
Matt Angert, Applied Physics Laboratory
David Israel, NASAs Goddard Space Flight Center

INTRODUCTION
Motivated by the recent interest in employing SmallSats for
deep space and interplanetary scientific research, this study
investigates the state-of-the-art in deep space SmallSat communications and tracking implementation and operation and
proposes improvements to them. This work includes surveys
of SmallSat communication equipment and operational strategies. We have examined the channel between spacecraft and
the ground network as well as the channel between pairs of
spacecraft. As the shortcomings of the existing systems and
operational procedures are unveiled, we investigate and then
make recommendations for the adoption of improvement
options. Our objective is to allow SmallSats to play a greater
role in deep space exploration by reducing the disparity

This article is the second in a three-part series. Part I can be
accessed in the July 2020 issue of A&E Systems Magazine;
Part III can be accessed in the August 2020 issue.
Authors' current addresses: F. Davarian, Sami Asmar,
J. Baker, J. Gao, R. Hodges, D. Landau, N. Lay, L. Torgerson,
and W. Walsh, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 USA (e-mail:
davarian@jpl.nasa.gov). M. Angert Applied Physics Laboratory, Laurel, MD 20723-6099 USA. D. Israel, NASA's Goddard Space Flight Center, Greenbelt, MD 20771 USA.
Manuscript received October 12, 2019, revised January
1, 2020, and ready for publication February 18, 2020.
Review handled by Peter K. Willett.
0885-8985/20/$26.00 ß 2020 IEEE
26

between the communication systems of larger, more expensive missions and SmallSats. "Improving Small Satellite
Communications and Tracking in Deep Space" summarizes the study in a three-parts article. We have provided surveys, analyses, and examples of missions,
existing or under development, in this series to support
our recommendations.
The direct-to-earth link was investigated in Part I, and
recommendations to improve the link were made to better
serve the user community. Among the topics we discussed
are the choice of radio frequency (RF), spacecraft emergency, size, power and mass of the radio equipment,
solid-state power amplifiers (SSPAs), and antennas.
This part of the series, Part II, extends the discussion
to other subjects of interest, including spacecraft tracking
and navigation (radio and optical), disruption-tolerant networking, and proximity links and protocols. Equipment
used for proximity links, such as radios and antennas, are
also discussed. Additionally, we provide a discussion on
the use of SmallSat communication links to perform radio
science measurements. Finally, we make our recommendations to improve the performance of the communications and tracking system of SmallSats in deep space.
In Part III of this series, we focus on the ground
support that is provided by NASA's Deep Space Network
(DSN). Because the number of SmallSats is expected to
grow faster than other users of the DSN, efficient operational schemes and improvements in SmallSats and
their communication systems are needed to avoid
network congestion so as to continue to serve the

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