• 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 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.
    • A NEW ERA IN WORLDWIDE TACTICAL COMMUNICATIONS

      Reid, Charles E. Jr; Naval Electronic Systems Command (International Foundation for Telemetering, 1973-10)
      The Fleet Satellite Communication System (FLEETSATCOM) now under development will provide the first U. S. military satellites designed from the start as operational transponders for tactical communications with and among mobile users. FLEETSATCOM is a logical outgrowth of earlier experimental projects, principally the Tactical Satellite Communication (TACSATCOM) project of the late 1960’s. When the globe-girdling system goes operational in calendar year 1976 it will quite literally revolutionize both Air Force and Navy tactical communications by providing availability and reliability of over-the-horizon communications that can never be matched by conventional high-frequency circuits.
    • HIGH DENSITY PCM MAGNETIC TAPE RECORDING

      Wells, Jon B.; Bell & Howell (International Foundation for Telemetering, 1973-10)
      The Bell & Howell Enhanced-NRZ™ recording reproducing technique for bit packing densities up to 40,000 per track inch is described in this paper. Utilization of the pulse code modulation format of Enhanced-NRZ achieves this high density with a bit error rate of one in ten million. Bell & Howell’s standard VR-3700B instrumentation tape recorder and wideband instrumentation recording tape are used. This same technique permits parallel recording of data rates up to 10 megabits per second at a tape speed of 120 in./s. The merits of the unique encoding/decoding method, factors affecting bit error rate, and future opportunities for development are discussed.
    • THE ADVANCED OPLE FOR SEARCH AND RESCUE

      Morakis, James C.; Rupp, Walter; National Aeronautics & Space Administration; Patuxent Naval Air Test Center (International Foundation for Telemetering, 1973-10)
      The OMEGA Position Location Experiment (OPLE) was performed in 1967 by the Goddard Space Flight Center in order to demonstrate a position location and data collection system. OMEGA navigation signals were received at a remote site and retransmitted via a synchronous satellite to a ground processing center where data collecting and position determination was performed. Recent technological advances have made it possible to develop an Advanced OPLE system towards a global search and rescue application. This application generated some new problem areas such as the OMEGA lane ambiguity, random access, location accuracy, real time processing, and size and weight of the Search and Rescue Communication (SARCOM). This experiment will demonstrate the feasibility of instantaneous alarm and position location by using a relatively inexpensive, battery operated, three-pound package. This package can transmit the alarm and position through a synchronous satellite to a search and rescue station in less than three minutes, in an environment of 50,000 to 100,000 subscribers drawn from the maritime, aircraft, recreational communities and others.
    • 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.
    • 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.
    • 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.
    • 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 PCM DATA SEQUENCE CONTROLLER

      Sandia Laboratories; Johnson, Charles S. (International Foundation for Telemetering, 1973-10)
      The PCM Data Sequence Controller described in this paper is used to interface a memory-controlled PCM encoder with a plated wire memory to form a unique digital data compression and storage system. The memory-controlled PCM encoder is used to select formats and convert input analog data channels into a PCM bit stream which is both transmitted and stored in a plated wire memory. The encoder is also used to retrieve information from the plated wire memory and retransmit it. The system provides both temporary and permanent data storage for the telemetering of data in a severe environment.
    • 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.
    • A SHORT RANGE 15 MEGABIT/S LED COMMUNICATOR

      Dworkin, L. U.; Coryell, L.; USAECOM (International Foundation for Telemetering, 1973-10)
      The design, development, and testing of a short range (distances up to 100 ft) data communications equipment that utilizes a GaAs light emitting diode (LED) source is discussed. Data rates of 15 Mb/s are accommodated by a transmission terminal which consists of a line of sight (LOS) atmospheric portion and a fiber optic link. The system has an all weather capability, is relatively inexpensive and is intended for tactical military applications. This is the first attempt at developing a wideband optical communicator that has a similtaneous LOS and cable capability often needed in a tactical military environment.
    • 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.
    • DATA RELIABILITY

      Powers, S.G.; Radiation (International Foundation for Telemetering, 1973-10)
      In this paper the problem of achieving reliable digital information transfer in the presence of data errors is addressed. The approach taken is to reject data which is suspected of being in error under the philosophy that it is better to miss data than to receive it incorrectly. To this end, error detection mechanisms are considered and their performance compared for a specific application. The mechanisms are thresholding, error detection coding, waveform error detection and feedback. It is shown that error detection coding is the most effective, followed by feedback, thresholding, then waveform error detection. The results are summarized in Tables I and II. These tables give the undetected word error rate and missed word rates for the techniques considered. The application which originally inspired this work is the use of time-division multiplexing to transfer mission-critical data on the B-1 aircraft.
    • THE D.O.T. CHANNEL SIMULATION AND MODEM TEST FACILITY

      Buck, R. E.; Frasco, L. A.; Salwen, H. C.; Transportation Systems Center; Proteon Associates (International Foundation for Telemetering, 1973-10)
      The characteristics and capabilities of a channel measurement and simulation facility are described. This facility has been established at the U. S. Department of Transportation, Transportation Systems Center. The system employs a RAKE type channel measurement system and a compatible digital equivalent tapped delay line channel simulator. The equipment has been used for the evaluation of digital communications problems created by the urban environment. It is currently being used to investigate the performance of modems under a variety of propagation conditions.
    • A PROGRAMMABLE SAMPLING FORMAT TELEMETRY SYSTEM

      Peterson, Max B.; Johns Hopkins University (International Foundation for Telemetering, 1973-10)
      This paper describes the programmable sampling format telemetry system to be used by the near-earth Small Astronomy Satellite-C (SAS-C) and possible future SAS missions. The concept of the programmable sampling format is introduced and the features of the system are illustrated by an example. The SAS-C telemetry system is described at the block diagram level and redundancy of the system is discussed briefly.
    • ULTRASOUND TELEMETRY OF FETAL CARDIAC ACTIVITY

      Hess, Orvan W.; Litvenko, Wasil; Yale University (International Foundation for Telemetering, 1973-10)
      Patterns of alterations in fetal heart rate provide the earliest clue of jeopardy of the fetus from umbilical cord compression, abnormal uterine contractions, placental dysfunction or impaired fetal reserve. Correlated with uterine contractions, such patterns provide an index of the condition of the fetus and an objective basis for clinical management. The recognition of the value of continuous monitoring of these parameters has resulted in widespread use of electronic apparatus. Telemetry techniques have proved value as an alternative method of surveillance. A system has been devised for telemetry of fetal cardiac activity detected with ultrasound.