• International Telemetering Conference Proceedings, Volume 09 (1973)

      Unknown author (International Foundation for Telemetering, 1973-10)
    • PLANETARY PROGRAM DATA SYSTEMS STANDARDS

      Glahn, Earl W.; Planatary Programs Data Systems Working Group (International Foundation for Telemetering, 1973-10)
    • A MULTI-PURPOSE, DUAL-CHANNEL MODEM FOR C/No THRESHOLD

      Baghdady, Elie J.; Info Systems (International Foundation for Telemetering, 1973-10)
      A description is given of a newly developed modem based on the synthesis of a constant-envelope quadra-phase signal with dual-channel frequencydivision multiplexing of analogvoice with data, data with data, time code With data, ranging signal with d:Ata, etc. The technique is capable of providing low-threshold operation down to carrier power-to-(noice power density) ratios, about 40 db, and includes a built-in, on-line measurement and display of the C/N(o) for quantitative performance monitoring purposes.
    • A REAL-TIME HADAMARD TRANSFORM SYSTEM FOR SPECIAL AND TEMPORAL REDUNDANCY REDUCTION IN TELEVISION

      Noble, S. C.; Knauer, S. C.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
      A digital Hadamard transform system has been developed for the real-time compression of standard NTSC television signals. The system digitizes the video signals and subdivides four successive frames of data into suppictures of sixty-four picture elements. The subpictures are cubes four elements on a side, in horizontal, vertical and temporal directions. Subpictures are transformed and processed to reduce special and temporal redundancy. Implementation and performance results of the system will be described and discussed.
    • THE DESIGN OF A SECOND GENERATION YAWSONDE

      Clay, Wallace H.; Mermagen, William H.; Ballistic Research Laboratories (International Foundation for Telemetering, 1973-10)
      Improvements have been incorporated into existing yawsonde telemeters to facilitate ground reduction of extensive quantities of data. The main area of improvement has been in the design of the amplifier so that solar pulses of constant amplitude and constant width can be transmitted to ground receiving stations. The new amplifier design makes it possible to reduce the solar pulse data on board the projectile itself providing solar aspect angle as a function of time of flight in binary coded form at the transmitter. Such on-board, real time motional data could be used in a command/control system to enhance the accuracy of artillery fire.
    • SIMULATION RESULTS FOR AN INNOVATIVE ANTIMULTIPATH DIGITAL RECEIVER

      Painter, J. H.; Wilson, L. R.; National Aeronautics and Space Administration; LTV Aerospace Corp. (International Foundation for Telemetering, 1973-10)
      Simulation results are presented for the error rate performance of the recursive digital MAP detector for known M-ary signals in multiplicative and additive Gaussian noise. The structure of the digital simulation of the innovative receiver, operating in a multipath environment, is generally described. Specific results are given for a quaternary signal, of the type used in air-ground data links, with 2500 symbol per second transmission rate. Plots of detection error rate versus additive signal to noise ratio are given, with multipath interference strength as a parameter. For comparison, the error rates of conventional coherent and noncoherent digital MAP detectors are simultaneously simulated and graphed. It is shown that with non-zero multiplicative noise, the error rates of the conventional detectors saturate at an irreducible level as additive signal to noise ratio increases. The error rate for the innovative detector continues to decrease rapidly with increasing additive signal to noise ratio. In the absence of multiplicative interference, the conventional coherent detector and the innovative detector are shown to exhibit identical performance.
    • RFI ANALYSIS APPLIED TO THE TDRSS SYSTEM

      Jenny, J.A.; ESL Incorporated (International Foundation for Telemetering, 1973-10)
      The effect of radio frequency interference (RFI) on the proposed Tracking and Data Relay Satellite System (TDRSS) was assessed. The method of assessing RFI was to create a discrete emitter listing containing all the required parameters of transmitters in the applicable VHF and UHF frequency bands. The transmitter and spacecraft receiver characteristics were used to calculate the RFI contribution due to each emitter. The individual contributions were summed to obtain the total impact in the operational bandwidth. Using an as yet incomplete enitter base, we have concluded that the 136-137 MHz band should be used by TDRS rather than the whole 136-138 MHz band because of the higher interference levels in the 137-138 MHz band. Even when restricting the link to 136 to 137 MHz, the existing link design is marginal and it is recommended that interference reduction units, such as the Adaptive Digital Filter, be incorporated in the TDRS ground station. RFI is less of a problem in the 400.5 to 401.5 MHz band and can probably be handled by restricting command transmissions to low RFI areas or if that is not acceptable, by using simple automatic notch filters to notch out the few interferers present.
    • THE REDUNDANCY OF A SIMPLE SYNCHRONIZATION METHOD FOR VARIABLE LENGTH CODES

      Shtarkov, Yu. M.; Academy of Sciences of the USSR (International Foundation for Telemetering, 1973-10)
      Prefix insertion prior to the coded representation of every fixed length block of data provides a simple synchronization method for variable length coding. Unlike fixed length coding where the prefix appears with a set period, the appearance time of each prefix word in the variable length coded representation is a random variable. At the receiver a synchronization decision is made whenever a pattern within a threshold Hamming distance of the prefix is received. In this paper an expression is found for small synchronization error probabilities. This egression depends on the coded block length only through its average value L. The optimal value for the recognition threshold is found. The necessary and sufficient condition for an arbitrarily small synchronization error probability is shown to be that the prefix length grows as log L. The results are discussed from the viewpoint of data compression and source encoding.
    • THE APPLICATIONS OF CODEM CONCEPTS FOR COMMUNICATIONS OVER THE AERONAUTICAL CHANNEL

      Chase, David; CNR, Inc. (International Foundation for Telemetering, 1973-10)
      The aeronautical channel characterized by multipath interference due to scattering and reflections off the surface of the earth represents a difficult channel for obtaining reliable data transmission. It is shown that interfering paths can be of sufficient strength and have Doppler spreads such that conventional forms of modulation are severely limited. In order to obtain error probabilities below 10^(-5) over a wide range of channel conditions, a robust signaling approach which is relatively insensitive to short term channel conditions is necessary. It is shown that these robust properties can be obtained by Codem concepts which jointly optimize the modem and coding design.
    • CROSSPLAY COMPATIBILITY OF WIDE-BAND TAPE RECORDER/REPRODUCERS

      Hartzler, F. R.; Hust, D. R.; Heberling, E. D.; Naval Missile Center (International Foundation for Telemetering, 1973-10)
      This paper describes the procedure and results of a series of tests on a cross section of tape recorders to determine the effects of record bias and record signal level on the quality of data recorded in the Pre-D (predetection) mode. FM (frequency modulation) and PCM (pulse code modulation) formats were used in the study. The tests were performed on tape recorders at five test sites to determine the effects of crossplay under typical operating conditions. The results are summarized and possible methods of improving crossplay data quality are suggested.
    • AN ALL DIGITAL LOW DATA RATE COMMUNICATION SYSTEM

      Chen, Chi-Hau; Fan, Maisie; Southeastern Massachusetts University (International Foundation for Telemetering, 1973-10)
      The advent of digital hardwares has made it feasible to implement many communication system components digitally. With the exception of frequency down conversion, the proposed low data rate communication system uses digital hardwares completely. Although the system is designed primarily for deep space communications with large frequency uncertainty and low signal-to-noise ratio, it is also suitable for other low data rate applications with time-shared operation among a number of channels. Emphasis is placed on the fast Fourier transform receiver and the automatic frequency control via digital filtering. The speed available from the digital system allows sophisticated signal processing to reduce frequency uncertainty and to increase the signal-to-noise ratio. The practical limitations of the system such as the finite register length are examined. It is concluded that the proposed all-digital system is not only technically feasible but also has potential cost reducation over the existing receiving systems.
    • USER-ORIENTED IMAGE DATA CARTRIDGE RECORDING SYSTEM

      Horton, Charles R.; Radio Corporation of America (International Foundation for Telemetering, 1973-10)
      New generation satellites such as ERTS present a new challenge to the data recording industry. Continuous wideband data creates an enormous storage/retrieval problem. Recently developed high density tape storage solves the volume problem but does not provide fast access. Clearly, some cartridge type device is required. A similar problem faced the broadcast T.V. industry. Cartridge equipment was developed to allow automatic programming of short segments. This paper describes application of this technology to present and future data storage requirements. With the technique described, ERTS data can be segmented into blocks of ten frames each and stored in easily accessed tape cartridges.
    • A HIGH SPEED AIRBORNE DATA ACQUISITION AND CONTROL SYSTEM WITH AN INTEGRATED DIGITAL COMPUTER

      Trover, William F.; Teledyne Controls Company (International Foundation for Telemetering, 1973-10)
      AIFTDS-4000 has been developed as a modularly expandable instrumentation and control system primarily for use in aircraft and system flight test. The bidirectional data processing capacity of Remote Multiplexer/Demultiplexer Unit, however, permits the system to be applied to data processing and control loop functions as well as the classical role of a data gathering system. The basic system was developed for NASA-FRC under three different contracts; NAS4-1848 (the ACS and RMDU’s), NAS4-1940 (the integrated signal conditioner cards) and, NAS4-1943 (the expanded test set). The system comprises Airborne Hardware, Ground Support Equipment and Software. The Airborne Hardware is divided into two major elements; The Airborne Computing System (ACS), and the Remote Multiplexer/Demultiplexer Unit (RMDU). Ground Support Equipment is presently restricted to the ACS Test Set (ACS/TS) which permits total checkout of the ACS without the RMDU’s or checkout of the full AIFTDS, as well as performing the function of an autonomous mini-data reduction ground station and the Portable Address Generator which permits testing of one RMDU (or one zone of the airplane) without the ACS or the ACS/TS. Software may be grouped into System Checkout and Diagnostic Software, Flight Test Program Software and Quick Look/Reduction Software. The prototype AIFTDS-4000 was qualified in two stages; the RMDU was qualified in October 1972 with the ACS qualified in April 1973. The Expanded Test Set and supporting software were delivered in May 1973.
    • VANGUARD/PLACE EXPERIMENT SYSTEM DESIGN AND TEST PLAN

      Taylor, Ralph E.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
      A system design and test plan are described for operational evaluation of the NASA-Goddard Position Location and Aircraft Communications Equipment (PLACE), at C-band (4/6GHz), using NASA’s ship, the USNS Vanguard, and the ATS-3 and ATS-5 synchronous satellites. The Sea Test phase, extending from March 29, 1973 to April 15, 1973 has been successfully completed; the principal objectives of the experiment were achieved. Typical PLACE-computed, position-location data is shown for the Vanguard. Position location and voice-quality measurements were excellent; ship position was determined within 2 nmi; high-quality, 2-way voice transmissions resulted as determined from audience participation, intelligibility and articulation-index analysis. A C-band/L-band satellite trilateration experiment is discussed.
    • A REVIEW OF MULTIPLE AMPLITUDE-PHASE DIGITAL SIGNALS

      Smith, Joel G.; California Institute of Technology (International Foundation for Telemetering, 1973-10)
      This paper reviews the data rate, error rate, and signal-to-noise ratio relationship for various uncoded M-ary digital amplitude modulation (AM), phase modulation (PM), and combined AM-PM systems. These signal systems have the common virtue that expanding the number of possible signals to be transmitted increases the data rate but not the bandwidth. The increased data rate generally requires an increased signal-to-noise ratio to maintain constant error probability performance. Thus, these systems use power to conserve bandwidth. A general treatment of the error rate of M-ary digital AM-PM permits development of a simple yet accurate expression which approximates the increase in average signal-to-noise ratio (over that of binary phase shift keying) required for constant error performance. This equation provides insight into why arrays differ in their signal-to-noise ratio requirements.
    • A 10.6 μm TERRESTRIAL COMMUNICATION LINK*

      Goodwin, Francis E.; Nussmeier, Thomas A.; Zavin, Jack E.; Hughes Research Laboratories; U. S. Army Electronics Command (International Foundation for Telemetering, 1973-10)
      This paper reports the development of an experimental type 10.6 μm laser communication system, consisting of a transmitter terminal and a receiver terminal, designed to operate one wav over a nominal five-mile path. The system provides a 5 MB/s digital data channel using a frequency shift keying format and optical heterodyne detection with a mercury cadmium telluride detector operating at a temperature of 77°K. The system is the first CO2 laser heterodyne communication system which is capable of hands-off, uninterrupted operation in a nonlaboratory environment. The achievement of single frequency operation of a laser transmitter and local oscillator in a field system is the result of more than seven years of research and development. Laser frequency purity, stability and control, all questions of primary concern previously, have been proven satisfactory with the development of this system. This paper reports the operation of the system during environmental tests, over a 4.1-mile test range, a 19.5-mile test range at the Hughes facility, and over a three mile test range at Ft. Monmouth, N.J. over a period of several months. During a period of 1320 hours of continuous operation, the system was inoperable for 65 hours due to weather conditions, demonstrating a reliability of 95%.
    • A SPACEBORNE RECEIVER FOR MEASURING ELECTROMAGNETIC FIELD INTENSITY

      Reich, B.W.; Van Dusen, M. R.; Habib, E. J.; National Oceanographic and Atmospheric Administration; Airborne Instrument Laboratory; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
      At the present time, considerable interference with communications to and from spacecraft has been experienced. Consequently, the need for determining the extent of this interference was indicated. NASA contracted AIL to design and build a very accurately controlled receiver to monitor the electromagnetic radiations in both existing and projected space communication bands. Based on analysis of the existing and projected space communication bands, 108 to 174 MHz, 240 to 478 MHz, and 1535 to 1665 MHz were covered. The receiver achieves accurate control via a digitally tuned synthesizer and a wide range of digital control including frequency band coverage and gain control selection. Digital memory was provided to store 16 separate digital command instructions which can be programmed via a command data link. The receiver provides for transmission to the ground of both a predetection signal and signals in digital format, which in turn, were provided by sampling and analog-to-digital conversions.
    • THE APPLICATION OF AEROSPACE TECHNIQUES TO AUTOMOTIVE CRASH TEST INSTRUMENTATION

      Jachman, J. J.; Ford Motor Company (International Foundation for Telemetering, 1973-10)
      The ultimate proof test of compliance with government safety standards for automobile “passive” occupant crash protection is obtained by crashing a test vehicle, occupied by instrumented anthropometric test dummies, into a concrete barrier. Each test of this type costs a minimum of $10,000, and much more if the vehicle is a prototype. The data that are obtained from the test dummies during such tests are the proof of compliance with the government safety standards and, therefore, must be highly reliable. Many aerospace techniques, such as a Metrology Laboratory, Quality Control, and redundancy can be adapted and utilized to maximize the reliability of the barrier crash data. These techniques are described and some early results are summarized. The early results show a marked improvement in data reliability compared to previous tests.
    • A SHOCK HARDENED PCM SYSTEM WITH DATA STORAGE

      Barnes, D. E.; Sandia Laboratories (International Foundation for Telemetering, 1973-10)
      A miniature shock hardened PCM system with data storage capability has been developed by Sandia Laboratories for use in test where RF transmission either difficult or impossible. The PCM has 16 channel input capacity and encodes the data with 6 bit accuracy. The data rate is selectable from 1k bit per second to 250 k bit per second. The encoder has been harbarized and packaged in a volume of less than 4 cubic inches. The data storage is selected in 6 k bit increments with a maximum storage of 600 k bits. Typical applications involving earth and water penetrating are described.
    • CRYSTAL-CONTROLLED HIGH-G TRANSMITTER

      Lange, Kenneth L.; Schell, Max V.; Hewlett-Packard; Sandia Laboratories (International Foundation for Telemetering, 1973-10)
      Continuous telemetering during and after a 10,000 to 16,000g shock pulse experienced by the telemeter is a requirement that is frequently not met. In most cases a free-running oscillator is used in the transmitter while a very wide band receiver is used to acquire and provide leeway for the drifting and shifting RF signals.