IEEE - Aerospace and Electronic Systems - September 2019 - 2

In This Issue -Technically
WATER ELECTROLYSIS PROPULSION AS A CASE STUDY IN RESOURCE-BASED SPACECRAFT ARCHITECTURE
(FEBRUARY 2020)
In situ resource utilization (ISRU), the use of materials available on-site to replenish supplies or manufacture components during
a mission, is vital to sustaining human presence in space. ISRU has been identified by NASA as one of the key technologies in
the Human Exploration Destination Systems Technology Area. In recent years, the abundance of water in the solar system has
been made increasingly clear. Extraterrestrial water, liquid water especially, is of great scientific interest, as targets where water
is available are often desirable for future exploration. ISRU with water is therefore a particularly high priority. This paper considers the implications of in situ water on the design of space systems, with the use of water for multiple purposes on the CisLunar
Explorers EM-1 secondary payload as a case study. Water onboard the CisLunar Explorers is used in every subsystem: as
propellant, for slosh-damping, as a heat sink, and as a radiation shield. The CisLunar Explorers spacecraft do not collect water in
situ but, instead, serve as a pathfinder for demonstrating the utility and versatility of water for future ISRU.

NANO SEMIHARD MOON LANDER: OMOTENASHI
The 6U CubeSat "OMOTENASHI," which is due to be launched in 2020 by NASA's Space Launch System, will be the world's
smallest moon lander. Its main mission is to present the possibility of nanomoon landers to enable distributed multipoint lunar
exploration and participation by the commercial sector. The severe mass and size limitations of OMOTENASHI make a soft
landing on the surface impossible, so instead a semihard landing scheme has been adopted. That is, a small solid rocket motor
will decelerate the spacecraft to around 50 m/s, followed by the use of shock absorption mechanisms for high-speed impact.
An ultrasmall telecommunication system (X-band and P-band) has also been developed. The spacecraft will also observe the
radiation environment between the Earth and the Moon using commercial portable dosimeters for future manned exploration.
This paper describes the mission objectives, the mission sequence, the spacecraft configuration, and the technologies developed
for OMOTENASHI.

THE IRIS DEEP-SPACE TRANSPONDER FOR THE SLS EM-1 SECONDARY PAYLOADS
The Jet Propulsion Laboratory (JPL) is supporting several deep-space CubeSat missions selected as secondary payloads on the
Space Launch System Exploration Mission One (SLS EM-1) launch of the Orion spacecraft. Seven secondary payload CubeSat
missions (Lunar Flashlight, Near-Earth Asteroid Scout, BioSentinel, Lunar IceCube, CubeSat for Solar Particles, Lunar Polar
Hydrogen Mapper, and ArgoMoon) have baselined the Iris deep space transponder as the main telecommunications and navigation
transponder for their missions. Iris, first developed for JPL's interplanetary nanospacecraft pathfinder in relevant environment mission, and further developed for JPL's Mars Cube One mission, is a software-defined radio based on various JPL flight heritage
designs. The transponder operates at X-band frequencies (7.2-GHz uplink, 8.4-GHz downlink) for compatibility with NASA's
Deep Space Network, but the modular hardware design allows for further expanded capabilities into other frequency bands such as
UHF, S-, and Ka-band. The transponder has a maximum power consumption of 35 W at 4-W radio frequency output, with uplink
sensitivities down to À150 dBm. Various encoding schemes are available for the user to choose, from traditional convolutional
coding with Reed Solomon concatenation to Turbo codes, and support for low-density parity-check coding is in the plan for future
support. This paper will discuss the current capabilities and specifications of the Iris deep space transponder, as well as current
hardware, firmware, and software implementations, and provide a short overview of future capabilities currently in the works.

REGENERATIVE RANGING FOR JPL SOFTWARE-DEFINED RADIOS
Communications and navigation are fundamental to robotic spacecraft exploration. NASA spacecraft communicates via radio
links with antennas in the deep space network (DSN) located in California, Australia, and Spain. Measurements of range between
the DSN and spacecraft are an important and sometimes critical contribution to navigation. For a given pair of uplink and downlink carriers, ranging must generally be accompanied by telemetering, in order to allow for efficient use of spacecraft and ground
resources. Regenerative ranging, which is compatible with the simultaneous presence of telemetry, is more efficient in the use of
link power than is the current standard (nonregenerative) ranging. This improved efficiency arises because regenerative ranging
replaces the wideband filter found in a nonregenerative transponder's ranging channel with a narrowband loop that tracks the
range code, so the signal-to-noise ratio in the transponder's ranging channel is large and there is essentially no noise modulated
onto the downlink carrier. This paper offers a comparison of pseudonoise (PN) regenerative ranging versus the nonregenerative
method of ranging. This paper also describes the implementation of PN regenerative ranging on the Iris transponder, which is a
low-power, 0.5U size, DSN-compatible, software-defined radio based on various JPL flight transponder designs. Iris is baselined
to be used on 7 out of 13 of the CubeSats flying as secondary payloads on the Space Launch System Exploration Mission-1
launch of the Orion spacecraft.

IEEE A&E SYSTEMS MAGAZINE

SEPTEMBER 2019

IEEE - Aerospace and Electronic Systems - September 2019

Table of Contents for the Digital Edition of IEEE - Aerospace and Electronic Systems - September 2019