Final Report for the Nimbus-D High Data Rate Storage System
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https://ntrs.nasa.gov/search.jsp?R=19700027148 2020-03-23T17:58:54+00:00Z / FINAL REPORT FOR THE NIMBUS-D HIGH DATA RATE STORAGE SYSTEM Contract No..NAS5-10396 Prepared by RCA IDefense Electronic Products Astro-Ejectronics DivisionJ Princeton, New Jersey for Goddard SpaceFlight Center National Aeronautics and SpaceAdministration Greenbelt, Maryland - . 9A9 (ACCESSION NUMBER) (THRU) O(PAGES) II qdP (CODE)i . (NASA CR OR TMX OR AD NUMBER) (CATEGORY) NATIONAL TECHNICAL [N. -NF IATIONSERVICE S'n~tV& z22151 FINAL REPORT FOR THE NIMBUS-D HIGH DATA RATE STORAGE SYSTEM Contract No. NAS5-10396 Prepared by RCA IDefense Electronic Products Astro-Electronics Division IPrinceton, New Jersey AED R-3548-F Issued: April 17, 1970 INTENTIONALLY LEFT BLANK PRECEDING PAGE BLANK NOT FILMED. PREFACE This report summarizes the work performed by the Astro- Electronics Division of the RCA Corporation for the Goddard Space Flight Center of the National Aeronautics and Space Administration under Contract NAS5-10396. The work was performed during the period starting April 28, 1967 and ending February 6, 1970. iii PRECEDING PAGE BLANK 'NOT FiLMED. SUMMARY AND CONCLUSIONS The HDRSS-D program required the development of a new two-frame center connected multiplexer, a slightly modified electronics module, and a modified tape transport. The last two items are basically the same as those used on the HDRSS-B program. The multiplexer, qualified at prototype levels, contains improved crys tal mounts, new adder and telemetry circuits, a modified IRIS channel, and a new VIP channel similar to the IRIS channel. The electronics module was modified to include a new VIP channel and a widened IRIS channel. The tape transport, oper ational during launch, contains a new brake mechanism, an optical end-of-tape sensor, and a method for cleaning the magnetic heads (Serial No. 08 only). Analysis of the test data from the prototype multiplexer and the flight model sys tems show conformance with the performance specifications contained in Section 2. The use of the widened IRIS channel did not have pronounced effects on the test results; however, analytical and empirical measurements on inter-symbol inter ference shows that detection of data transmitted from the satellite and via the long lines will be improved. Bit Error rate tests of the VIP and IRIS channels using the worst-case word pattern produced test results well below specifications. Linearity, signal-to-noise and amplitude response of the THIR and ID channels were far better than the specified levels. The time code channel valley-to-peak ratio was more stringently controlled than specified by tailoring the adjustment to a specific multiplexer prior to system tests. A complete data summary is contained in Section 8. A number of improvements applicable to the basic tape transport are recommended for future programs; specifically, high inertia idlers, abrasive head cleaner, a two-speed bi-directional motor, and development of a new method to anchor the tape to the reels. During the Nimbus-Ill mission a significant 3400 Hz flutter component appeared on the VIP channel data. Tests conducted at RCA have shown that high inertia idlers will reduce the 3400 Hz flutter component below the inherent noise level of the tape transport. An abrasive oxide, formulated during prototype life tests, was added to a section of the magnetic tape between the optical end-of-tape and the mechanical end-of tape switches. With a special command sequence, the abrasive can be commanded over the heads at controlled intervals. Tests conducted on a tape-life test setup at RCA have increased the usefulness of the tape recorder by 30 percent. The time interval between cleanings was 30 days. v SUMMARY AND CONCLUSIONS (Continued) A two-speed bi-directional motor is presently under development at RCA. The use of this motor would eliminate the entire planetary assembly. This will in crease reliability as ten bearings and four mylar drivebelts would be eliminated. This change will not affect the physical size of the tape transport. Development of a new method to anchor the magnetic tape is recommended to eliminate tape splice imprinting. Tape splice imprinting was detected by the Illinois Institute of Technology and Research Institute (IITRI) under an independent study contract issued by NASA. vi TABLE OF CONTENTS. Section Page Preface ........... .................................... iii Summary and Conclusions......................... v 1. INTRODUCTION A. Puipose of Report ........ .................. ....... 1 B. Contract Objectives ............... ......... .......... 1 C.. HDRSS Historical Data ................................. 1 1. Contract Modification .... ......................... 2 2. Technical Directives ............ ...... ........... 4 3. Equipment Transfers and Schedules ............ ........ 7 D. HDRSS Operational Description .......................... 8 1. Spacecraft Equipment ............................. 10 2. Ground Station Equipment . 10 3. Test Equipment. .................... ............. 13 2- SYSTEM PERFORMANCE OBJECTIVES A. ID Channel ......................................... 15 B. THIR Channel ................................ ..... 16 C. Time Code Channel ................................... 16 D. Biphase Channels ................. ..... ......... 17 3 SPACECRAFT EQUIPMENT A. General ........................................ 19 B. Tape Recorder Assemfbly ............... ..... ... 19 C. Multiplexer Assembly ................................ 21 4 DESIGN CHANGES A. Introduction ........... 2r2.......... B. Tape Recorder Changes ......... ........ 25 1 Balanced Disk Brake ..................... ........ 25 2. End-of Tape Sensors .............................. 26 3. Tape/Head Configuration Changes ...................... 29 4. AC Erase Head .................................. .30 C. Multiplexer Changes ................. ... c 30 D. Ground Station Changes ............. ... .. ... 31 1. Introduction ................................. 31 2. Demultiplexer ............ ....................... 31 vii TABLE OF CONTENTS (Cont'd) Section. Page 3. THIR Demodulator Drawers .......................... , 33 4. Balanced Line Amplifier.................................a33 5. Monitor Circuits ................................. 33 6. THIR-6 Detector and Control Circuit .............. ........ 33 E. Bench Check Unit Changes ......................... ..... 34 1. General ........... ........... ..... ............ 34 2. Signal Selector Chassis ... ....................... 34 3. Demultiplexer ................ ...................... 34 4. THIR Demodulator Drawer ................. ........... 34 5. RF Link Simulator .................................. 35 6. Clock Simulator .................................. 35 7. THIR Simulator ..................................... 35 8. 400 Hz Phase Detector ................... .......... 35 9. AC Erase Interface Assembly ......................... 35 5 VIP, TC, and ID CHANNEL ANALYSIS A. Introduction ................................. ...... 37 1. HDRSS-D Sign Characteristics and Performance Objectives ...... 37 2. HDRSS-D Frequency Division Multiplexed Spectrum, Frequency Deviations, and RF Inboard Power ............... 37 3. Summary of S-band Link Characteristics .................. 37 B. VIP Channel Analysis ................................... 41 1. Introduction ...... ............................... 41 2. ChannelAnalysis Trade-offs .......................... 41 3. Circuit Description .................................. 44 4. Theoretical Considerations for Single Sideband Amplitude Modulation ...................... ........ 49 5. Bit Synchronizer SNR Requirements ................ 52 6. System Design Considerations .... ............ ....... 54 7. VIP System Performance Analysis ....................... 71 C. Time Code Channel Analysis ............................ 78 D. THIR Channel Analysis ........... .................. ... 79' 1. Introduction ....... .............................. 79 2. Signal-to Noise Ratio ..... .............. .. .......... 79 6 BENCH CHECK UNIT AND TEST EQUIPMENT A. Bench Check Unit ....................................... 81 1. Purpose of Bench Check Unit. ......................... 81 2. Spacecraft Equipment Test ........................... 82 B. Demultiplexer Test Set ........................... 84 viif TABLE OF CONTENTS (Cont'd) Section Page 7 SYSTEM TEST DESCRIPTIONS A. Introduction .. .................................. 87 B. Test Plan........................................... 87 1. Board Level Tests ............... ............... 87 2. Module Level Tests .... ........................ 87 3. System Level Tests ............... ............... 88 C. Spacecraft Subsystem Performance Tests.............. 89 1. Operational Tests .... ........... .............. 90 2. System Go No-Go Test ............. .............. 90 3. Transport Go No-Go Test .......................... 91 4. Module GoNo-GoTest ............ .............. 91 5. Leak Rate Test .... ............................. 91 D. Bench Check Unit Tests .............................. 91 E. Ground Station Equipment Tests ............... 92 F.- Environmental Tests .......................... 92 1. Multiplexer ... ........ ................................ 92 2. Engineering Model Environmental Tests ............ .. 94 3. Flight Model Environmental Tests ..................... 94 8 SYSTEM TEST DATA SUMMARY A. Introduction ..... ... .. .. ................. 97 B. Data Summary .................................... 98 9 LIST OF REFERENCES 121 Appendix I. HDRSS-D SIGNAL-TO-DISTORTION