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Overview of Electrical Systems for Proposed Instrument Networks

This document provides detailed information on power bus, grounding, connections, and network interfaces for the proposed instrument networks. Specific guidelines for power consumption, data rates, and network interfaces are discussed.

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Overview of Electrical Systems for Proposed Instrument Networks

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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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