Aerospace and Electronic Systems - April 2019 - 25

Desai et al.

Figure 7.
(A) Block diagram of the SwRI SATYR single board computer. (B) Photograph of the CuSP Flight Board.

SPARC8 processor integrated with heritage Consultative
Committee for Space Data Systems (CCSDS)-compliant
command and telemetry interface, instrument data interface, ADCS interface, EPS interface, and payload instrument interface designs. Note that CuSP does not use the
CCSDS interface since the IRIS transponder provides this
function.

ELECTRICAL POWER SYSTEM
The CuSP EPS is a COTS system consisting of eight solar
panels (two triple-deployed solar arrays, two fixed-body
solar arrays), a set of Battery Charge Converters (one for
each solar panel), two 40 Wh battery packs, and direct
current/direct current (dc/dc) converters producing 3.3, 5,
and 12-V regulated outputs. This subsystem is supplied by
Clyde Space. At operating temperature, the solar arrays
produce $40 W of raw power which results in $35 W of
regulated power available to subsystems and instruments.
This low power availability is sufficient for all modes by
using load cycling between the science instruments and
the transponder. The battery pack, a 2s8p arrangement of
Lithium-Polymer pouch cells, is sized to support initial
operation during detumbling and to supplement solar array
power during the power negative data downlink operations, which occur once per week. Each 40-Wh battery
pack has high and low side inhibits to prevent operation
during launch and prior to deployment. Additionally, they
are equipped with overcharge, overdischarge, overcurrent,
overvoltage, and undertemperature protections. All components have space flight heritage.

ATTITUDE DETERMINATION AND CONTROL SYSTEM
The CuSP ADCS consists of two subsystems both of
which are COTS units: the XACT unit is supplied by Blue
Canyon Tech and the Reaction Control Subsystem is a
0.3U cold gas Micro-Propulsion System (MiPS) provided
by VACCO Industries. Both units have space flight
APRIL 2019

heritage. The XACT is equipped with three reaction
wheels, two sun sensors, and a star tracker to achieve
Æ0.007 of pointing accuracy and knowledge, or better,
for all three axes. When enabled by the s/c, the XACT is
designed to handle reaction wheel inertia shedding by
directly commanding the VACCO without s/c intervention. The VACCO MiPS is sized to support inertia shedding (to prevent reaction wheel saturation caused by orbit
precession) during and after detumbling operation, after
each communication maneuver. No delta-V operations are
required to adjust the orbit.

TELECOMMUNICATION SYSTEM
CuSP utilizes the IRIS V2.1 Deep-Space Transponder,
developed by JPL, for all communications to a NASA 34m Deep Space Network (DSN) antenna. The IRIS, capable
of multiple frequency support, has an X-Band transceiver
"slice," which interfaces to its main control board and to
an external Low Noise Amplifier with two low-gain antennas (LGA) and an external 4-W Solid State Power Amplifier (SSPA) with one $24-dBi transmit medium gain
antenna (MGA) and one $5 dBi LGA. All four antennas
are microstrip patch antennas with a single patch for the
LGAs and a 64-patch array for the MGA. All three LGAs
are 2p sr, wide angle antennas, while the MGA has a 9.5
3 dB beamwidth. All transmission operations will take
place at 8000 b/s while receive operations will be 1000 b/
s. The transmit LGA is intended only for initial DSN
contact after which time the XACT system can fine-point
the MGA. CuSP closes its 3-month mission link budget,
including a possible 6-month extension, exceeding a 6 dB
margin. Each DSN contact consists of a tracking contact,
data downlink, and command uplink. Initial DSN contact
will consist of two 4-h contacts, commissioning consists
of three 4-h contacts, and science operation has 14 weekly
4-h contacts through the duration of the mission.
One week's worth of telemetry equates to $73 Mb and
requires 2.52 h (of the 4 h per contact) to downlink. The

IEEE A&E SYSTEMS MAGAZINE

Aerospace and Electronic Systems - April 2019

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