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COMM Subgroup

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).

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COMM Subgroup

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  1. 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)

  2. 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)

  3. 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)

  4. 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)

  5. 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)

  6. COMM: Overview Satellite Satellite must be able to: • Receive data from the space shuttle • Transmit data to the space shuttle Wireless LAN Transceiver Tx Satellite Computer Rx Receive Commands Transmit Photos Space Shuttle Orbiter Tomo Sugano (6/15)

  7. COMM: Operational Schematic Satellite Space Shuttle Image Buffer Tx Downlink Uplink Rx FCS CPU CPU Rx Uplink Downlink Tx Archival RAM Memory LAN LAN Data Flow Tomo Sugano (7/15)

  8. 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)

  9. 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)

  10. 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)

  11. 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)

  12. 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)

  13. 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)

  14. System Integration – Overall Scheme Flight Computer POWER FCS COMM ADCS Output Orbit Control Output Other Outputs Sensors Tomo Sugano (14/15)

  15. System Integration – Data Connections Star Tracker Spin Wheels Thrusters GPS1 GPS2 Serial 2 Serial 3 Serial 4 Serial 5 Flight Computer Serial 1 FCS PWR Flow Digital I/O USB 1 USB 2 Wireless LAN Archival Memory POWER Camera Tomo Sugano (15/15)

  16. Conclusion Thank you for your attention!

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