I- NASA TECHNICAL NOTE c 00 00 nP z c 4 m 4 z LOAN COPY: RETURN TO AFWL (WLIL-2) KIRTLAND AFB, N MEX NIMBUS TI FLIGHT EVALUATION AND ENGINEERING REPORT, LAUNCH THROUGH ORBIT 5275 bY Joseph J. McNaney und Rennie A. Palmer GeneruZ E Zectric Compuny UBd Ra@h Shupiro Goddurd Spuce FZight Center -- /. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. FEBRUARY 1969 TECH LIBRARY KAFB. NM 0131510 NASA TN D-4881 NIMBUS I1 FLIGHT EVALUATION AND ENGINEERING REPORT, LAUNCH THROUGH ORBIT 5275 By Joseph J. McNaney and Bennie A. Palmer General Electric Company Ralph Shapiro Goddard Space Flight Center Greenbelt, Md. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 22151 - CFSTI price $3.00 I ABSTRACT Nimbus II, an earth-stabilized, long-life observatory satellite, is part of the NASA research and development program for meteorological applications. Experiments include advanced vidicon camera subsystem (AVCS), high-resolution infrared radiometer (HRIR) subsystem, medium- resolution infrared radiometer (MRIR) subsystem, automatic picture transmission (APT) subsystem with data code grid, and direct readout infrared radiometer (DRIR). This report covers the flight history of Nimbus II from its launch on May 15, 1966, through orbit 5275on June 15, 1967, providing an engineering evaluation of the performance during this period. The mission successfully met all technological and scientific objectives, the only failures being the tape recorders, PCM, MRIR, AVCS, and HRIR; these failures occurred during orbits 949,985, 1443, and 2455, respectively. As of March 15, 1968 (22 months, orbit 9020), the space- craft was performing satisfactorily with little change in performance since June 15, 1967, except for the solar array drive. After October 1967, the drive system evidenced occasional erratic behavior and since then has been operated in the high-torque mode. The real-time data sys- tems are still being used. ii CONTENTS Abstract ......................................................... ii SECTION1-INTRODUCTION ........................................... 1 SECTION 2-FLIGHT OBJECTIVES....................................... 3 SECTION 3-VEHICLE DESCRIPTION AND FLIGHT SUMMARY ................... 7 SPACECRAFT DESCRIPTION ....................................... 7 Structure .................................................. 7 Thermal Control ............................................. 7 Stabilization and Control ........................................ 8 Power Supply ................................................ 8 Command Clock .............................................. 8 Command Receiver ............................................ 9 Telemetry .................................................. 9 Communications .............................................. 9 Advanced Vidicon Camera System (AVCS)............................. 10 High-Resolution Infrared Radiometer (HRIR)........................... 10 Automatic Picture Transmission (APT) Subsystem and Direct Readout (DRIR) .... 10 Medium-Resolution Infrared Radiometer (MRIR) ........................ 11 NIMBUS SPACECRAFT CHANGES .................................. 11 CONFIGURATION................................................ 12 FLIGHT HISTORY ............................................... 13 Launch and Orbit Insertion ....................................... 13 Initial Spacecraft Activation ...................................... 15 Significant Orbital Events ....................................... 15 Orbit- Sun Relationships ......................................... 19 Current Status ............................................... 19 SECTION 4-POWER SUBSYSTEM ....................................... 21 FUNCTIONAL DESCRIPTION ........................................ 21 Solar Acquisition ............................................. 21 Energy Conversion ............................................ 22 Battery Operation............................................. 22 Voltage Regulation and Distribution ................................. 22 FLIGHT OBJECTIVES AND SUMMARY OF OPERATION ..................... 23 POWER SYSTEM PERFORMANCE .................................... 23 Solar Array Performance ....................................... 23 Power Storage ............................................... 30 iii CONTENTS (Continued) Voltage Regulation ............................................ 39 Telemetry Sensor Errors ........................................ 39 SOLAR CELL EXPERIMENT........................................ 41 Description ................................................. 41 Discussion ................................................. 41 SECTION 5-CONTROLS SUBSYSTEM ..................................... 43 DESCRIPTION .................................................. 43 Functional Description ......................................... 43 Physical Description........................................... 43 FLIGHT OBJECTIVES ............................................ 48 DISCUSSION ................................................... 49 Launch and Initial Stabilization .................................... 49 Satellite Day-to-Night Transition .................................. 49 Satellite Night-to-Day Transition .................................. 50 IR Disturbances .............................................. 51 Roll Yaw Momentum Exch$nge .................................... 51 Pitch Disturbance Torque ....................................... 52 Solar Array Drive Pointing ...................................... 52 Power Conversion ............................................ 54 Temperature Maintenance ....................................... 54 Pneumatics ................................................. 55 Solar Eclipses ............................................... 56 Fine Sun Sensors (Yaw Sun Sensors) ................................ 58 Attitude Error Analysis ......................................... 58 SECTION 6-THERMAL SUBSYSTEM ..................................... 61 DESCRIPTION .................................................. 61 Functional Description ......................................... 61 Physical Description ........................................... 61 FLIGHT OBJECTIVE ............................................ 62 DISCUSSION ................................................... 62 General ................................................... 62 Orbital Trends ............................................... 62 SECTION 7-COMMAND SUBSYSTEM ..................................... 75 SUBSYSTEM OPERATION .......................................... 75 FUNCTIONAL DE SCRIPTION ........................................ 75 iv CONTENTS (Continued) Command Receiver ............................................ 75 Command Clock Functional Description .............................. 76 FLIGHT OBJECTIVES ............................................ 78 RESULTS OF FLIGHT OPERATION (LAUNCH THROUGH ORBIT 5275) .......... 78 COMMAND RECEIVER OPERATION ................................... 79 Unencoded Command Executions ................................... 79 Command Receiver EMI ........................................ 81 Suspected Redundant FM Demodulator Problem ......................... 81 COMMAND CLOCK OPERATION ..................................... 82 Clock Time Reference .......................................... 82 Clock Frequency Reference ...................................... 84 Noise Entry into Clock Memory ................................... 85 Command Problems ........................................... 88 Clock Exercises ............................................. 91 Matrix Current Monitor Telemetry Levels ............................ 92 Command Capability at STADAN Stations ............................. 92 SECTION8-PCM SUBSYSTEM ......................................... 95 FUNCTIONAL DESCRIPTION ........................................ 95 FLIGHT OBJECTIVES ............................................ 95 DISCUSSION ................................................... 95 Beacon Power ............................................... 96 Signal Acquisition ............................................. 97 Signal Quality ............................................... 97 Recorder Tape Degradation ...................................... 98 PCM Tape Recorder Failure ..................................... 98 Effects of EMI on Telemetry Levels ................................ 100 Current Subsystem Status ....................................... 101 SECTION 9-AVC SUBSYSTEM AND S-BAND TRANSMITTER .................... 103 INTRODUCTION................................................. 103 DESCRIPTION .................................................. 103 FLIGHT OBJECTIVES ............................................ 106 AVCSubsystem .............................................. 106 S-band Transmitter Flight Objectives ............................... 106 ELECTROMECHANICAL PERFORMANCE ............................... 107 V CONTENTS (Continued) Camera Components .......................................... 108 Electronic Components ........................................ 114 Recorder Components ......................................... 115 S-band Components........................................... 120 VIDEO QUALITY ............................................... 120 Vidicon Response ............................................ 121 Interference ............................................... 121 Night