• STANDARDS FOR GOVERNMENT USE OF THE SPECTRUM

      Hull, Joseph A.; IRAC Technical Subcommittee (International Foundation for Telemetering, 1973-10)
    • A SYNCHRONIZED DISCRETE ADDRESS BEACON SYSTEM

      Blake, Neal A.; Federal Aviation Administration (International Foundation for Telemetering, 1973-10)
      The Federal Aviation Administration is developing a Discrete Address Beacon System as a new air traffic control surveillance system. It will solve most of the problems of the present beacon system and will also provide an integral digital data-link for ground to air messages. This paper describes a particular implementation of the DABS concept which also provides air-to-air collision avoidance service and navigation service.
    • TELEMETERING VIA LEAKY WAVEGUIDES

      Hu, A. S.; New Mexico State University (International Foundation for Telemetering, 1973-10)
      Telemetering through leaky waveguides is a combination of cable transmission and atmospheric transmission. This system carries radio signals in a confined space tube thus making signal transmission through tunnels, mines, and buildings possible. This paper discusses the history of development, the types of leaky waveguide, the transmission characteristics, and the performance evaluation methods.
    • TIME DOMAIN ANALYSIS OF AN AGC WEIGHTED COMBINER

      Hill, E. R.; Naval Missile Center (International Foundation for Telemetering, 1973-10)
      The conventional agc weighted diversity combiner is implemented on the assumption that the agc system of each receiver is tracking the rf fading envelope perfectly (i.e., such as to maintain the linear i-f output amplitude constant). The departure from optimum (maximal-ratio) combining which results from imperfect tracking is determined by computer solution of the nonlinear differential equation of the agc system for particular deterministic rf fading envelopes. The performance of the agc weighted combiner is compared with maximal-ratio and equal-gain combiners, both as a function of time and fade rate. It is shown that under certain conditions the equal-gain combiner outperforms the agc weighted combiner. It is also shown that by using both the a-m (detected linear i-f envelope) and the agc voltages for weighting the combiner the limitations arising from the response time of the agc system can be overcome. It is also indicated how an optimum diversity selector can be implemented by using both the a-m and agc voltages.
    • TIMING CORRELATION IN TELEMETRY RECORDING AND PROCESSING SYSTEMS

      Matthews, F. L.; Streich, R. G.; Vandenberg Air Force Base (International Foundation for Telemetering, 1973-10)
      The Space and Missile Test Center (SAMTEC) has conducted tests to correlate independent data stream to within ±10 microseconds. System timing error measurements have been made to determine RF system delays; the delays associated with wideband analog tape recorders in the recording, dubbing and reproducing processes; and uncertainties associated with processed data. Comparison of the time delays between predetection PCM data and post-detection PCM data are made. Several methods of recording IRIG time code formats A and B are evaluated for best resolution. Timing error versus tape recorder head azimuth is plotted. Tape recorder phase delay effects on time code formats and on PCM data are given. The time bias between the time tag and the computer processed data is presented. Sources of timing errors and the calibration and operating techniques available to minimize these errors are discussed. A special time tag technique (Ref 1) has been used in the past to determine the cumulative timing bias for all sources. This investigation is believed to be the first attempt to identify the individual contributions to the cumulative bias.
    • TRACKING AND DATA RELAY SATELLITE SYSTEM (TDRSS)

      Barritt, Paul; Clark, George; NASA (International Foundation for Telemetering, 1973-10)
      Coincident with the advent of the Space Shuttle era in the late 1970’s will also come a new era in space communications. The NASA Tracking and Data Relay Satellite System (TDRSS), consisting of satellites in synchronous orbit relaying data between mission spacecraft in low altitude earth orbit and the various mission control centers, will change the character of tracking and data acquisition operations from the short duration, intermittent contacts characteristics of the world wide network of ground stations of the Space Tracking and Data Network (STDN), to nearly full time contact. This capability will expedite interaction between ground based scientists and their spaceborne instruments, reduce dependence upon data tape recorders, and in general improve the reliability and versatility of space communications. This paper will discuss the requirements for TDRSS service and the characteristics of the system and subsystems that NASA studies have shown best meet those requirements.
    • 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.
    • 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.
    • 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.
    • UNIVERSAL AIR-GROUND DATA LINK SYSTEM

      Williamson, Thomas; Federal Aviation Administration (International Foundation for Telemetering, 1973-10)
      With the implementation of a nationwide Air Traffic Control (ATC) automation system nearly completed the Department of Transportation/Federal Aviation Administration is devoting considerable attention to the integration of a data link capability into the system. This paper presents a description of the universal data link system and details of the system’s characteristics. A possible configuration of the data link system with the ATC automation system is also presented.
    • 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.
    • 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 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.