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Optimizing Communication and Delta-V Strategies for Satellite and Space Shuttle Operations

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16 diapositives · 306 Views · Sep 09, 2014

This document provides an overview of the tasks and computations performed by Tomo Sugano in optimizing satellite operations in coordination with the Space Shuttle. It focuses on the challenges of differential drag compensation, communications, and system integration for on-board flight computers. Key findings include the need for Delta-V to maintain the satellite's position relative to the shuttle, the calculations for atmospheric drag, and the selection of communication devices for efficient data transfer. It concludes with insights into system integration for reliable performance.

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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!