IEEE Aerospace and Electronic Systems Magazine - July 2020 - 11

Davarian et al.
Table 3.

Communications Features of Deep Space 6U CubeSat Missions (BPSK Modulation)
Mission

Bit rates, b/s

Transmit
power

Antenna
gain

X-transmit

62.5-8000

29 dBi

X-receive

62.5-1000

N/A

9 dBi

UHF-receive
(relay)

8000

N/A

3 dBi

Mars, support InSight Entry,
Descent, and Landing (EDL) at Mars.
Functioned as a bent pipe, receiving
data from InSight UHF link,
transmitting data to Earth on Xband link.

NEA Scout

62.5-1000

23 dBi

1991 VG asteroid

BioSentinel

62.5-8000

23 dBi

Earth-trailing orbit (heliocentric)

CuSP

8000

24 dBi

Heliocentric

MarCO

Frequency
bands

DTE LINKS
This section addresses the satellite-to-ground link. This link
can be provided using radio or optical signals. The "Direct-toEarth Links Using Radio Waveforms" section discusses links
using radio waveforms and the "Optical Communications"
section discusses links using optical waveforms.

DTE LINKS USING RADIO WAVEFORMS
This section investigates the performance of SmallSat
communication links based on data provided in Table 1.
For completeness, a brief review of existing deep space
and lunar SmallSats and their communications features is
presented in the following sections.

PRESENT COMMUNICATIONS
CAPABILITY
This section provides a discussion of existing (or soon to be
launched) deep space and lunar SmallSat communication
capabilities. These capabilities are investigated to establish a

Destination

baseline for proposing improvements-existing features are
used as a reference for making recommendations. Table 3
illustrates communication capabilities of MarCO, a pair of
planetary SmallSats that completed their mission in 2018.
The table also includes three other SmallSats that will be
launched in late 2020 for deep space activities, Near-Earth
Asteroid (NEA) Scout, BioSentinel, and CubeSat to study
Solar Particles (CuSP)-all four examples are 6U CubeSats.
The takeaways from Table 3 are the following: for the
four existing samples of deep space CubeSat missions, the
maximum spacecraft RF power is 4 W, maximum antenna
gain is 29 dBi, and maximum downlink data rate is 8 kb/s.
This study explores ways of improving on the above figures with the objective of increasing the DTE data rate for
future SmallSat missions. In another example, Table 4
provides similar data for four lunar 6U missions scheduled
for launch in late 2020 together with nine other CubeSats,
including NEA Scout, BioSentinel, and CuSP (a total of
13 will be launched together). Due to the shorter range to
Earth, higher data rates are supported by the lunar missions. For example, the Lunar Flashlight spacecraft can
support a data rate of 256 kb/s. It is noteworthy that Omotenashi, a Japanese CubeSat, intends to land on the moon.

Table 4.

Communications Features of CubeSat Missions to the Moon, Scheduled for Launched Late 2020
Mission

Comm frequency bands

Bit rates

RF transmit power

Antenna gain

Destination

Lunar flashlight

X-up/X-down

62.5-256000 b/s

7.5 dBi

Moon polar orbit

Luna H-Map

X-up/X-down

62.5-128000 b/s

7 dBi

Moon polar orbit

1 W (S) 1.25 W (X)

7 dBi (S) 7 dBi (X)

Moon landing

6.3 W (UHF) 4 W (X)

0 dBi (UHF) 5 dBi (X)

Moon polar orbit

Omotenashi

Lunar IceCube

JULY 2020

UHF (details unknown)

1 kbps (S)

S-down X-up/X-down

8 bps-262.144 kb/s (X)

UHF-up/down X-up/

38.4 kbps (UHF)

down

62.5 b/s-256 kb/s

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