CubeSats @ AIAA SmallSat Conference
*.Sat & GeneSat-1 Overview
Eric Lee, *.Sat Project Manager
http://ssdl.stanford.edu/stardotsat/
leeep@stanford.edu
8 August 2004
Utah State University
Logan, UT
AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Introduction
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Today’s Primary Goal…
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*.Sat Mission Statement
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High-level overview of services provided by the *.Sat Spacecraft
Bus to the GeneSat-1 Mission Payload Module
To provide a standard CubeSat Bus as a support platform for
educational and scientific space experiments.
Nomenclature
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*.Sat CubeSat Bus (covers Ground Segment and Space Vehicle)
GeneSat-1 Mission and Payload
8 August 2004
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Agenda
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Topics of discussion
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Basic requirements
Design status
Spacecraft/Bus layout
System interfaces
GeneSat-1 Mission Payload
Bus Services to payload (Subsystems)
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Basic Requirements
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“Standard” Bus
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Primary Payload
Primary Payload
Primary Payload
Bus Module
LEO Orbit
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Adherence to the CubeSat
Design Specification
Modular configuration
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1.0, 1.0, 1.0
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1.5, 1.0, 0.5
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2.0, 1.0 (no active ADCS)
Standardized interface(s)
Fly as secondary payload
One-year Design Cycle
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Bus Module
Must be complete on 30
September 2004 in a “flightready” configuration
24 June 2004
Secondary Payload
Bus Module
Secondary Payload
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Design Status
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Heritage
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NemaSat Bus Program, 2003
 Lead by Mike Gonzales
Current status
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Electronics are fabricated and in test
Structure fabricated and undergoing Alodine processing
Environmental testing to begin in September timeframe
Software programming and testing ongoing
On track for delivery of hardware 30 September 2004. Validation
and test may not be complete.
Payload integration with initial EDU in November 2004
Launch slated for Autumn 2005 aboard Dnepr (SS-18) LV
24 June 2004
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Spacecraft layout
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“Triple Cube”
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100x100mm
“footprint”
340mm long
3kg mass
P/L Module
Bus Module
ADCS Module
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Bus Layout
EPS
Z-axis coil
Magnetometer
Batteries
C&DH
ADCS PCB
Patch Antenna
Sun Sensor
24 June 2004
WedgeLock
Plate
ADS Gyros/Accels
Payload I/F
Backplane
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
System Interfaces
Primary Payload
Digital/Analog/I2C
I/O
Solar Arrays
Unregulated Power
Bus Module
Digital/Analog/I2C
I/O
2.4 GHz Link
Ground Station
Unregulated Power
Secondary
Payload
24 June 2004
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
NASA/Ames Astrobionics GeneSat-1 Payload
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Self-contained genetic research experiment
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Gene-expression in E. coli bacteria
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8-10 wells
Fluidic media
Optical sensor system
Micro-g environment
Space radiation
In-Situ Genetics (ISGEN)
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GeneSat-1 is a precursor to the future ISGEN (InSitu Genetics) missions (bigger bird)
Will fly other increasingly complex organisms
Opportunities for launches up to twice per year
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Data/Power Flow
UNREG
Primary Payload
EPS
Voltage
Regulator
Payload
Data
Charge
controller
Battery
UNREG
Data
REG
Payload
Memory
UNREG
Solar Arrays (4)
Bus Sensors
REG
Data
SEU/Latchup
Mitigation
P/L MCU
Mux
(ADG732)
Data
Temp
Data
Mux
(ADG732)
Data
V and I
Data
Payload Data
Analog/Digital/I2C
REG
REG
ADCS Actuators
Control
REG
ADCS
Sensors
Data
Data
PIC18F6720
MCU
I2C
Voltage
Regulator
C&DH
Payload Data
Analog/Digital/I2C
ADCS (Secondary Payload)
Data
Data (RS-232)
115.2 kbps
ADCS MCU
WDT
Flash
Memory
Comm
(Microhard
MHX-2400)
2.4 GHz Link (86 kbps)
Ground Station
Data
24 June 2004
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Bus Services to Payload
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Attitude Determination and Control (ADCS)
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Passive ADCS (“Zero-Cube” option)
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Permanent magnets and hysteresis rods
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Pointing aligned to Earth’s magnetic field
“Active” magnetic torque system
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Onboard orbit propagator and magnetic field
model
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Sun sensors and magnetometer
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“B-dot” rate-damping and Nadir-Pointing
modes
Communications
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2.4 GHz ISM-band radio (Microhard MHX-2400)
Circularly-polarized patch antenna (up to 8dBi
gain)
Up/Downlink of data/telemetry/commands
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Bus Services to Payload (continued)
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Command and Data Handling
(C&DH)
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PIC18F6720-based architecture
Three banks SPI Flash memory (2 MB
each)
S/C health monitoring (T, V, I,
accels/rates)
Single-event upset and latch-up mitigation
Dual payload interfaces
Software
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Salvo Pro RTOS
Time stamping and data exchange w/
payload (via I2C)
Command set for Payload(s)
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Bus Services to Payload (continued)
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Electrical Power (EPS)
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28% Spectrolab UTJ cells on four body
panels (8 cells/panel)
Unregulated Bus Voltage to Payload(s)
2.0 – 4.0W peak power to Payload(s)
Protection circuits (hardware-based latch-up
mitigation)
Hysteresis discharge protection for Li-Ion
battery banks
Structures
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Standardized mechanical interface
Payload module may be designed by
customer if desired
Alodined 7075 Aluminum frames fabricated
with Electrical Discharge Machining (EDM)
process
Anodized 5050 Aluminum sheet metal body
panels
24 June 2004
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Bus Services to Payload (continued)
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Thermal
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Computer simulation in Thermal Desktop/SINDA
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Bus operational range from +10°C to +70°C
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-10°C to +75°C range for hardware allowables
Bus thermally isolated from Payload(s)
Primary payload has access to cold-plate open to
space
Thermally benign environment for biological payload
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+3°C to +37°C ±3°C survival range
Ground station
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6-meter dish at Stanford
Full-motion tracking
Mercury Ground Station software (Internet-based
infrastructure)
24 June 2004
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AIAA SmallSat Conference / *.Sat & GeneSat-1 Bus Overview
Questions and comments?
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Key supporters
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NASA/Ames Astrobionics
 John Hines and Bruce Yost
Space Technology Center
 Dave Engelbert
Stanford University Space Systems Development Laboratory
(SSDL)
 Professor Bob Twiggs
CalPoly CubeSat Team
 Professor Jordi Puig-Suari
Contact
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http://ssdl.stanford.edu/stardotsat/
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