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Electrical Systems

Electrical Systems. LROC. LOLA. LEND. SAM. LAMP. PSE. Diviner. EVD. ST. IMU. EVD. CRaTER. Propulsion. Switched Services. OM. IRW (4). CSS (8). BM. Battery. Proposed Instrument Networks. S-Band. Low-Rate. Comm. High-Speed Network. High-Gain Antenna. High-Rate. SSR.

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Electrical Systems

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  1. Electrical Systems

  2. LROC LOLA LEND SAM LAMP PSE Diviner EVD ST IMU EVD CRaTER Propulsion Switched Services OM IRW (4) CSS (8) BM Battery Proposed Instrument Networks S-Band Low-Rate Comm High-Speed Network High-Gain Antenna High-Rate SSR Ka-Band Low-Speed Network SBC Analog / Discretes Servo Drive HIDEC Power Bus LVPC Solar Array Main Avionics Thermal Pump Power & Switching Control Philip Luers / 561 2/15/2005

  3. Electrical Systems • General LRO Electrical Systems ICD is in review with Systems Team, sent to S/C team last week, main points of interest are: • Power Bus • +21 to +35 at LOLA harness connector, multiple wires, non-redundant bus • Tolerate 0 to 40 without damage • LOLA Instrument KO presentation shows +24 to + 32, is this a problem? • S/C PSE will use SSPC for switching, so there will be inrush specification • Fuses on S/C PSE only • Power bus ripple: < 1.0Vp-p (1 Hz – 10 MHz), < 0.5Vp-p (> 10 MHz) • Isolate primary return from chassis, single-point-ground in S/C PSE • Tie Secondary ground to chassis (< 0.5 milliohms) • Tie all chassis of instrument to spacecraft chassis (<2.5 milliohms) • Copper ground straps (5:1 length:width) where necessary • Blankets redundantly tied to spacecraft chassis • 2 ground tabs for 1 m2, add’l tab for every add’l m2 Philip Luers / 561 2/15/2005

  4. LROC Accommodations • Data • 3.5 Mbps, 300 Gbits/day • Power Consumption • 26.4 watts average, 36 watts peak (with 20% reserves) • Timekeeping • 1 pulse-per-second RS-422 pulse, active high for 30.5 +/- 1 microsecond • Time at Tone was message to accompany every pulse • Discrete commands • None identified • Additional Interfaces • Two thermistors will be provided by S/C to be mounted on outside of LROC instrument • Yellow Springs Instruments p/n 44907-07S7R6 or equivalent (S311-P-18-05A) and 5 kohm bias resistor for range of -30C to +70C Philip Luers / 561 2/15/2005

  5. LROC Network Interface • SpaceWire • We believe that SpaceWire will have a positive mission-level impact on • Spacecraft ICDs, simulators, and integration and test at the mission level • We have provided documentation to describe the core that would be provided and supported by Code 561 • We would like to hear results of study of Spacewire as primary interface for LROC Philip Luers / 561 2/15/2005

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