comm subgroup tomo sugano (primarily served as comm personnel) tasks –started out by helping...
Post on 23-Dec-2015
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COMM Subgroup
Tomo Sugano (Primarily served as COMM personnel)
• Tasks– Started out by helping Relative Orbit team
with differential delta-V requirement and GN2 mass
– Communication Scheme of the mission– System Integration (on-board flight
computer)
Tomo Sugano (1/15)
Differential Drag Compensation
• Ballistic coefficients different between satellite and shuttle
• Difference in drag forces (i.e. acceleration) exists.
• (B-Coeff. of Shuttle) >> (B-Coeff. of Satellite)
• Satellite must expend Delta-V to keep up with space shuttle.
Tomo Sugano (2/15)
Computations• Atmospheric drag acceleration (Da):
• Drag acceleration difference between the two spacecraft:
STS: S = 64.1 m2, CD = 2.0, m = 104,000 kg (orbiter typical)
Sat: S = 0.385 m2 (nominal), CD = 3.0 (worst case), m = 50 kg
Tomo Sugano (3/15)
Computations (cont’d)
• Orbiter speed (assuming circular orbit)
• Definition of Delta-V (or specific impulse)
• Mass expenditure of propellant (i.e. GN2 cold gas)
Tomo Sugano (4/15)
Results
• Using Isp = 65 sec; assume 50 kg for satellite weight
• Conclusions- At the typical 300 km LEO, Delta-V for 1 day mission is 1.36 m/s- Satellite will need at least 107 grams of GN2 to compensate drag- In addition to this Delta-V, we have orbit transfer Delta-V and ADCS Delta-V.
How we determined tank size.
Tomo Sugano (5/18)
COMM: Overview
• Receive data from the space shuttle
• Transmit data to the space shuttle
Satellite
Computer
Tx
Rx
Wireless LAN Transceiver
SatelliteSatellite must be able to:
Space Shuttle Orbiter
Receive Commands
Transmit PhotosTomo Sugano (6/15)
COMM: Operational Schematic
Satellite Space Shuttle
FCSCPU
ImageBuffer
ArchivalMemory LAN
Tx
TxRx
RxDownlink
DownlinkUplink
Uplink
LANRAM
Data Flow
Tomo Sugano (7/15)
CPU
COMM: Communication Devices
Local Area Network (LAN) Protocol is utilized.
Satellite- A Zonet light-weight
wireless LAN transceiver
Space Shuttle- An integrated wireless
LAN transceiver of a Panasonic Toughbook
Tomo Sugano (8/15)
COMM: Zonet Wireless LAN USB Adapter
• Model: Zonet ZEW2502 802.11g USB Adapter
• Dimensions: 93.5 x 27.5 x 10 mm • Mass: 32.0 grams• Transfer Rate: 54Mbps (nominal)• Uplink (Receive): 260 mW• Downlink (Transmit): 350 mW• Frequency: - 2.412GHz ~ 2.4835GHz
- S-band (space approved, open band)Tomo Sugano (9/15)
COMM: Antenna Modification
• Zonet LAN adapter uses “Microstrip antenna.”
• Compact and reliable for short-distance communication.
• Directly attach antenna on the face of satellite
Tomo Sugano (10/15)
COMM: Image Transfer
• Estimated size of each image: 14-16 Mb• Our LAN protocol and devices allow nominal
54Mbps with pier-to-pier method.• Virtually no cause of appreciable noise in
space between satellite and space shuttle• Transfer time of each image: less than a few
seconds.• Image buffer need not to be large - A few GB USB jump drive recommended.
Tomo Sugano (11/15)
Selection of System Integration CPU
• System integration is core of the FCS Selection of flight computer CPU
• Arcom VIPER 400 MHz CPU found viable• VIPER is suitable because of its
- Light weight, 96 grams- Operable temperature range
-40 C to + 85 C- Windows Embedded feature
easy to program- Computation speed, 400 MHz- Memory capacity, up to 64MB of SDRAM- 5 serial ports- USB ports enables utilization of Zonet LAN adapter & jump drive
VIPER CPU board top view
Tomo Sugano (12/15)
Control System Integration - Overview
• ADCS and Orbit Rectification Computations
• Execute ADCS and Orbit Rectification• In-flight image capture handling • Data archiving
Tomo Sugano (13/15)
System Integration – Overall Scheme
Flight Computer
FCS COMM
Sensors
POWER
ADCS Output
Orbit Control Output
Other Outputs
Tomo Sugano (14/15)
System Integration – Data Connections
Star Tracker Spin Wheels GPS1Thrusters GPS2
Flight Computer
FCS
POWER
Serial 1
Serial 2 Serial 3 Serial 4 Serial 5
PWR FlowUSB 1 USB 2
Wireless
LAN
Archival Memory
Camera
Digital I/O
Tomo Sugano (15/15)
Conclusion
Thank you for your attention!
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