• PLANETARY PROGRAM DATA SYSTEMS STANDARDS

      Glahn, Earl W.; Planatary Programs Data Systems Working Group (International Foundation for Telemetering, 1973-10)
    • International Telemetering Conference Proceedings, Volume 09 (1973)

      Unknown author (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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • MULTISTATE ANALOG AND DIGITAL INTEGRATED CIRCUITS

      Abraham, George; US Naval Research Laboratory (International Foundation for Telemetering, 1973-10)
      Several independent physical phenomena in unipolar and bipolar semiconductor pn junction devices and integrated structures lead to voltage and current-controlled negative resistance without the use of external feedback. These include avalanche breakdown, quantum mechanical tunneling, and minority carrier storage. Two complementary types of negative resistances may be utilized as a basis for generating multistable energy levels. The number of stable states and their relative spacings can be readily varied. Without negative resistance interaction, M+1 stable states can be generated where M is the number of negative resistance devices involved. With negative resistance interactions, additional multistability occurs, resulting in a total number of (M+1) + (M-1)!stable states. S-S, N-N, and S-N interactions are analyzed. In the latter case, complementary negative resistances can be made to annihilate each other. Multistate tunnel and avalanche negative resistances have been made to occur in single devices resulting in tristable, quadristable and higher order energy levels. Variable radix counters, oscillators, frequency dividers, and high density memory elements have been fabricated both as hybrid and monolithic integrated circuits.
    • A HIGH CAPACITY, HIGH DATA RATE INSTRUMENTATION TAPE RECORDER SYSTEM

      Bessette, O. E.; Radio Corporation of America Recording Systems (International Foundation for Telemetering, 1973-10)
      A 240-megabit/second, serial bit stream recording system using a longitudinal (fixed-head) magnetic recording technique called HDMR (High Density Multitrack Recording) has been developed. This system provides maximum bits per square inch of tape at reliable in-track packing densities. Unique “unitized” fabrication techniques have been used to construct single stack magnetic heads (record/play on the same head) at track densities of over 100 tracks per inch. Commercially available tape is accommodated by the use of error detection and correction. HDMR technology, applied to the implementation of a typical ground instrumentation recording system, allows key performance parameters of: 240 Mb/s serial data input, 108 in/s tape speed, a 142-track head, a bit error rate of 1 x 10^-6 and 240 Mb/s serial data output.
    • THE INFLUENCE OF CARRIER FREQUENCY ON SNR FOR FM SYSTEMS

      Monson J. E.; Harvey Mudd College (International Foundation for Telemetering, 1973-10)
      The influence of carrier frequency on broadband signal-to-noise ratio is derived for a frequency modulated tape recording system. Optimum signal-to-noise performance occurs at the value of carrier frequency where the carrier-to-noise ratio is falling at 6 dB/octave. Signal-to-noise ratio is relatively insensitive to changes in carrier frequency about the optimum value.
    • AN ULTRAHIGH RATE DIGITAL TAPE RECORDER FOR SPACECRAFT APPLICATIONS

      Thompson, C. R.; Treadwell, R. J.; Powell, C.; FICA; NASA (International Foundation for Telemetering, 1973-10)
      Spaceborne digital recorders must satisfy the conflicting requirements of maximum data storage of high rate data (particularly for high resolution sensor data) and a long life with high reliability (meaning rugged design and moderate head-to-tape speeds). The multitrack longitudinal (fixed head) recorder can successfully resolve this conflict and satisfy both requirements. The evolutionary machine described herein was originally designed to store and reproduce 30 min of 39.9-Mb/s sensor data, for mission lives on the order of 1 year; newer designs have surpassed these parameters by significant amounts.
    • TRANSMISSION OF RADIOMETER DATA FROM THE SYNCHRONOUS METEOROLOGICAL SATELLITE

      Davies, Richard S.; Philco-Ford Corporation (International Foundation for Telemetering, 1973-10)
      The Synchronous Meteorological Satellite uses a spin scanner radiometer which generates eight visual signals and two infrared signals. These signals are multiplexed and converted into a 28-Mbps data stream. This signal is transmitted to ground by quadriphase modulation at 1686.1 MHz. On the ground, the digital signal is reconstructed to an analog signal. To conserve bandwidth, an analog-to-digital converter with a nonlinear transfer function was used for the visual signals. The size of the quantization step was made proportional to the noise output of the scanner photomultiplier tube which increases as the square root of incident light. The radiometer data transmission link was simulated on a digital computer to determine the transfer function. Some results of the simulation are shown.
    • APPENDIX A: TWELFTH ANNUAL REPORT OF THE TELEMETERING STANDARDS COORDINATION COMMITTEE

      Muller, Ronald M.; TELEMETERING STANDARDS COORDINATION COMMITTEE (International Foundation for Telemetering, 1973-10)
      The Telemetering Standards Coordination Committee (TSCC) was formed in 1960 and has been in continuous operation since that time. It is now sponsored by the ISA and the ITC and its membership is drawn from a wide cross-section of the telemetering community. Thus the views of Government, industry, user and manufacturer are brought out when any standard is reviewed by the committee. In accordance with its charter the TSCC is charged with the following tasks: establishing what standards, methods, and procedures are in existence and published; examining the technical adequacy of existing and proposed documents; exploring the need for new standards, methods, and procedures and promulgating the derivation of new documents. The TSCC does not issue standards, but rather acts as a review, coordinating, and fact-finding body, endorsing specific standards, methods, and procedures, and making recommendations to the appropriate document originating groups, to telemetry users and manufacturers, and the Government agencies. For further information on the origination of the TSCC and its original Charter and Bylaws, please see the 1962 Proceedings of the National Telemetering Conference. An annual report has been published each year since that time. Years 1963 through 1967 may be found in the NTC Proceedings of that year and, starting 1968 and all following years, may be found in the Proceedings of the International Telemetering Conference.
    • 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.
    • SPECTRUM PROCESSING RECEIVERS FOR TELEMETRY APPLICATIONS

      Van Cleave, J. R.; American Electriconic Laboratories, Inc. (International Foundation for Telemetering, 1973-10)
      When the i-f filter of a telemetry receiver is replaced by a digital processor utilizing an intermediate orthogonal transformation into either the frequency domain using Fast Fourier Transform (FFT) or sequency domain using Fast Walsh Transform (FWT), then much improvement in performance may be expected. This paper discusses both application and results of FFT and FWT processing to: 1) a signal acquisition receiver providing extremely enhanced phase lock loop (PLL) acquisition speed; 2) an adaptive i-f bandwidth receiver providing a large i-f signal to noise ratio (SNR) improvement and also immunity to undesired EMI and/or jamming signals; and, 3) a signal evaluation receiver for measurement of SNR in the range of -30 dB and up. Spectrum processor design considerations and tradeoffs are presented.
    • 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.
    • A VIDEO BANDWIDTH HE-NE LASER COMMUNICATION SYSTEM

      Pao, Yoh-Han; Freeman, J.P.; Allen, J.W.; Claspy, P.C.; Laser Communications Inc.; Case Institute of Technology (International Foundation for Telemetering, 1973-10)
      A He-Ne laser communication system with video bandwidth capability is described. The system is suitable for the transmission of video signals generally compatible with U.S. commercial practice, and the transmission of digital data at rates of approximately 10 to 1000 Kb/s, over ranges extending from a few hundred feet to about 10 miles. Relative to cable systems and microwave links, this laser system has the advantages of immunity from electromagnetic noise and from microwave interference, ease of installation, comparative freedom from regulation, mobile operation and lower costs. Possible occasional outages due to inclement weather constitute the principal drawback. This system is different from two other available types of optical links. The light emitting diode (LED) links are limited to short ranges and the laser injection diode (LID) links have low duty cycles and are not designed for video capability. The performance characteristics and operating data of a specific system, the LCI-203 system of LASER COMMUNICATIONS, INC. , are described in detail. Operating ranges and corresponding reliability figures are estimated for various geographical locations. Operating experiences in health care delivery and security surveillance applications are described.