IEEE Aerospace and Electronic Systems Magazine - July 2020 - 4

In This Issue -Technically
IMPROVING SMALL SATELLITE COMMUNICATIONS IN DEEP SPACE-A REVIEW OF THE
EXISTING SYSTEMS AND TECHNOLOGIES WITH RECOMMENDATIONS FOR IMPROVEMENT.
PART I: DIRECT TO EARTH LINKS AND SMALLSAT TELECOMMUNICATIONS EQUIPMENT
Robotic exploration of the solar system using small satellites (SmallSats) is gaining popularity because of
SmallSats' lower cost and faster development cycle compared to primary science missions. A potential
obstacle for deployment of SmallSats in deep space is the limitation associated with the communications
link imposed by SmallSats' frugal power and antenna size. These technical limitations constrain the range
and throughput of SmallSats and may impact their navigation performance. To allow SmallSats to play a
greater role in deep space science endeavors, we propose an enhanced communications architecture that will
lessen the communications disparity between larger, more expensive missions and SmallSats. The objectives
of the study are to define a communications architecture, in-flight and flight-to-ground, that is needed for
planetary SmallSats, both standalone or in support of a larger mission; and to develop a guideline for primary
spacecraft that would communicate with ride-along SmallSats. This work treats the space segment and the
ground network as a whole to provide for improvements not only via investments in technology, but also via
improvements in operational procedures. The study includes reviews of current communication concepts,
technologies, and procedures, as well as an assessment of navigation needs, evaluation of the communication
architecture performance for a range of destinations and applications, and identification of any gaps in
capability. The study product is a set of recommendations to space agencies and the planetary SmallSat
community. The main thrust of these recommendations is investment in technology, such as radios,
antennas, protocols, and methodologies. The concepts for improving communications capability of deep
space SmallSats are discussed in a series of three articles, Improving Small Satellite Communications in
Deep Space. In this article, Part I, we discuss SmallSat direct-to-Earth links, as well as SmallSat communications equipment. In Part II, we discuss navigation topics, proximity links and networks, and the use of the
communications channel for science observations. We present the ground network in Part III. Definitions
and assumptions are provided here in Part I.

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
This article is the second of a three-part series in which we present the results of a study exploring concepts
for improving communications and tracking capabilities of deep space SmallSats. In Part I, we discussed
SmallSat direct-to-earth links and SmallSat communications equipment, and provided recommendations for
future work. In Part II, we focus on SmallSat navigation options, Disruption Tolerant Networking (DTN),
proximity links, and the use of the communication link for science observations, and we provide recommendations for future work. We have examined both radio and optical navigation options, and considered autonomous and semiautonomous navigation to reduce operational costs for planetary SmallSats. We note that
communication link resilience to delay and disruption enhances spacecraft autonomy; therefore, we have
provided a discussion of DTN to indicate that using DTN allows for automated data transmission and
recovery, therefore, reducing manual operations. SmallSats in deep space may utilize a relay spacecraft
for communications with earth or function as a relay for landed and in-orbit assets. We present a detailed
examination of relay proximity links and networks where we address both proximity hardware and
networking scenarios. The proximity link features that we examine include the network architecture and its
relationship to DTN, proximity radios and antennas, communications link performance, and proximity
navigation. The use of the communication link for science has been practiced by primary missions in deep
space scenarios. (Two examples of past planetary radio science experiments can be found in the following:
https://solarsystem.nasa.gov/missions/cassini/mission/spacecraft/cassini-orbiter/radio-science-subsystem/
and https://www.boulder.swri.edu/pkb/ssr/ssr-rex.pdf). Likewise, SmallSats can offer their radio links for
radio science investigations. This article provides a brief introduction to radio science and presents
the prerequisite features necessary for radio science observations by SmallSats. We conclude with nine
recommendations based on the findings of the study. These recommendations are guidelines on the design,
implementation, and operation of deep space SmallSat communication links. The adoption of some or all
of the guidelines should result in an enhanced communication and tracking capability for the deep space
SmallSat missions.

IEEE A&E SYSTEMS MAGAZINE

JULY 2020

https://solarsystem.nasa.gov/missions/cassini/mission/spacecraft/cassini-orbiter/radio-science-subsystem/ https://www.boulder.swri.edu/pkb/ssr/ssr-rex.pdf

IEEE Aerospace and Electronic Systems Magazine - July 2020

Table of Contents for the Digital Edition of IEEE Aerospace and Electronic Systems Magazine - July 2020