1. Team NatSat
InSPiRESat Presentation
2016 INSPIRE Workshop
July 21, 2016
Team Members:
Aubrey Harris III
Antonio Oliveira
Brendan Perry
Jake Sullivan
Presenters:
Linda Schmidt
Amanda Slagle
1
2. Outline
• Mission Design and Sequencing
• Launch Vehicle and Propulsion
• Structure
• Electrical Power System (EPS)
• Thermal Control System
• Attitude Control System (ACS)
• Command & Data Handling (C&DH)
• Telecommunications
• Risks
• System Block Diagram
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6. Launch Vehicle
• Polar Space Launch Vehicle (PSLV)
• Provided by Indian Space Research Organization (ISRO)
• 600 km circular orbit
• Proven Launch History
• 33/35 successful on-orbit
deliveries
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8. Structural Conceptual Design
● Resist loads imposed during launching phase and minimize
deformation that could impair the functionality of the solar
panels and mechanisms
● Remain functional at the temperature range from -80°C to
+120°C
● Avoid damaging or transmitting excessive loads to the payload
during the launching phase
● Provide enough damping in the solar panels for the proper
operation of the Attitude Control System
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12. FEA Analysis
Stress (MPa) Frame Spider
Von Mises 45 70
Maximum Principal 52 75
Displacement (mm)
Total displacement 0.01 0.39
Maximum X 0.04 -0.07
Maximum Y -0.01 -0.39
Maximum Z +/-0.04 ~0
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13. Electrical Power System (EPS)
Requirements
• The EPS system shall provide a nominal voltage
level & sufficient power to the spacecraft
• The EPS system shall employ electrical fault
protection
• The EPS system shall provide telemetry to determine
payload power consumption to within 1 W
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18. Thermal Control Requirements
• NatSat thermal management system shall ensure
that all subsystem components remain within
operational temperatures
• Cryocooler radiator shall remain below -20°C while
dissipating 2W of power
Instrument Temperature Range (°C)
DWTS Cryocooler Radiator < -20
Nanopower BPX Battery -5 to 20
Solar Arrays -150 to 100
P60 Power Module -40 to 85
ISIS On Board Computer -25 to 65
BCT XACT ACS -20 to 50
Tethers SLX+UTX Transceiver -20 to 50
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19. Thermal Environment During Orbit
• Approximate time of orbit: 96 minutes
• Illuminated: 60 minutes
- Direct Solar
- Albedo
- Earth IR
- Internal Heat Dissipation
• Shadow: 36 minutes
- Earth IR
- Internal Heat Dissipation
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20. NatSat Thermal Control
• 1st order min and max temperature calculations:
• Solar arrays
• Cryocooler radiator
• External structure
- Iterations of materials
Material Coverage % Max Temp °C Min Temp °C Absorbance Emissivity
Polished 6061 Aluminum 100 310 255 0.2 0.03
Black Paint 100 28 -34 0.98 0.87
White Paint 100 -9 -33 0.25 0.9
Silverized FEP Teflon 100 -6 -20 0.08 0.66
OSR Quartz Over Silver 100 -16 -29 0.077 0.79
Black/White Checkered 100 10 -35 0.61 0.89
Aluminized FEP Teflon 100 -11 -30 0.16 0.8
6061 Alum/FEP Teflon 25/75 6 -15 0.17 0.61
6061 Alum/FEP Teflon 50/50 32 7 0.18 0.42
6061 Alum/FEP Teflon 40/60 21 -3 0.18 0.49
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23. NatSat Thermal Control System
* Contingent
upon lab testing
Equipment Manufacturer Surface Area (cm²) Mass (g) Power (W)
AZ93 White Paint AZ Technologies 1200 29
6061 Aluminum Local Procurement 2675 658
FEP Teflon Fluorogistx 1485 49
OSR Quartz over Silver Radiator Qioptiq 400 23
Battery Heater GOMSpace *6
Total 759 *6
• Thermal control of NatSat is achieved with a
fully passive system
• Simple, low risk design
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24. Attitude Determination and Control
• NatSat Attitude Determination and Control (ACS) shall
provide sufficient control authority, accuracy, and
stability to accomplish the mission science objectives
• ACS responsibilities include:
• De-tumbling after launch vehicle separation
• Maintaining accurate pointing knowledge
• Maintaining stable attitude
• Orienting vehicle for science operations
• Slewing vehicle for payload calibration
• Re-orienting vehicle to protect spacecraft optics
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26. ACS Control Performance
• ACS must reject disturbance torques and store momentum
• Worst-Case Disturbance Torque Estimates:
• External Torques: 1.16 x 10-6 N-m
• Internal Torques: 8.28 x 10-5 N-m
• Total: 8.40 x 10-5 N-m (RW maximum: 4 x 10-3 N-m)
• Momentum Accumulation
• External Torques: 6.74 x 10-3 N-m-s per orbit
• Internal Torques: 8.28 x 10-5 N-m-s per orbit
• RW Capacity: 1.374 x 10-2 N-m-s
• Momentum dump after 2 orbits (BOL) or 1.5 orbits (EOL)
• Likely longer given conservative estimates
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27. ACS Control Performance
• ACS must provide slew rate for sensor calibration
• Single RW can provide 4 mN-m for 3.44 sec
• Minimum slew rate:
• Largest vehicle moment of inertia: 0.5305 kg-m2
• Angular Acceleration: 0.432 deg/s2
• Angular Rate: 1.49 deg/s
• NatSat ACS provides sufficient attitude knowledge
accuracy, stability, and control authority to
accomplish the science mission objectives
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28. Command and Data Handling
Requirements
● Adequate command and data handling for
spacecraft control and configuration and
system health and status data gathering
● Storage and playback of 120 hours of data
● Storage and execution of 2 days of sequence
commands
● Autonomous initialization
● Reprogrammability
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31. System Architecture
• Processing
distributed among
C&DH, EPS, ACS,
and Telecomm
subsystems
• Time slice
architecture
Store
DWTS
data
Store
commands Check
command
buffer
Collect
subsystem
health &
statusAssemble
telemetry
packets
Send
telemetry
Check for
anomalies
Pet
watchdog
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32. C&DH Modes and Safing
• Launch: detumble, enable Telecomm and
ACS, achieve power positivity
• Operational: collect and transmit science and
engineering data, monitor system health
•Safe: conserve power, transmit limited
engineering data, recover from anomalies
•limit monitors
•watchdog
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33. Telecommunication
• Dual S-Band and UHF capabilities to meet daily data
requirements and minimize power usage
• Prioritizing S-Band for downlink and UHF for uplink
• Total daily coverage to 4 ground stations ~ 108
minutes with a maximum single pass of 14 minutes
• Utilizing existing ground station infrastructure to
include 3m and 6.1m dish
• Link Margin > 30 dB
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36. Telecommunication
• Utilize S-Band patch antenna with 6 dB of gain and
UHF dipole antenna with 0 dB of gain
• Customized 1U antennas both mounted to the nadir
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