• 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%.
    • ADAPTIVE ANTENNA ARRAY

      Smith, James M.; Sielman, Peter F.; AIL (International Foundation for Telemetering, 1973-10)
      A key problem in establishing and maintaining high quality communication repeater links among users, where the vehicle for retransmission is a synchronous orbit communications satellite, is that of enhancing the limited effective radiated power (ERP) capabilities of the smaller user against the not always so limited ERP capabilities of co-users or other sources of rf interference. The adaptive array which can supply narrow high gain custom shaped individualized beams weighted to reflect the ratio of user power to thermal noise and at the same time minimize the capacity reducing effects of intentional or unintentional rf interference emitters appears to be the most effective means of improving overall performance at least system cost.
    • 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.
    • AIFTDS-4000, A FLEXIBLE HIGH SPEED DATA ACQUISITION SYSTEM

      Borek, Robert W.; Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
      The data acquisition system of today’s research aircraft generally consists of a multiplicity of “black boxes” linked together by wiring cables of various lengths and sizes. This approach offers the user an “off-the shelf” type of flexibility to which he has become accustomed. It does not, however, provide for all the needs of an results demanded by today’s technology. The rising costs of flight test hours, the sophisticated airframes, and the minimum flight time allotted for actual flight test indicate a need to review existing data acquisition system technology and apply up-to-date technology. The NASA Flight Research Center at Edwards, California, initiated a review of its needs in the area of airborne data acquisition systems. The result was a new and powerful system called “AIFTDS-4000” (Airborne Integrated Flight Test Data System). AIFTDS is a high speed computer-controlled PCM system comprised of three basic units, the remote multiplexer de-multiplexer unit, the PCM processor, and the memory unit. The three units were designed and tested to meet the requirements of pertinent Mil-Specs for high performance aircraft. The signal conditioning, sensor excitation, and time code generator were designed as an integral part of the system and are not separate chassis. This paper discusses the design objectives established prior to actual hardware construction and compares these objectives with the final hardware.
    • 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.
    • 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.
    • 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.
    • ASTRODRIVE - A NEW POWER-CONSERVING TAPE DRIVE

      Karsh, Irving; Bell & Howell (International Foundation for Telemetering, 1973-10)
      Astrodrive® is a regenerative magnetic tape drive providing tape speeds from 15/16 to 960 in./sec. The unit features mechanical simplicity and low power consumption, in a unique peripheral drive mechanism, suitable for cartridge-load, or conventional reel-to-reel transport arrangements. Both single and dual motor configurations of the basic mechanism are discussed, along with the inherent capabilities and limitations of each.
    • THE ATS-F RADIO FREQUENCY INTERFERENCE MEASUREMENT EXPERIMENT

      Henry, Varice F.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
    • COORDINATION OF TELEMETRY STANDARDS

      Muller, Ronald M.; Telemetering Standards Coordination Committee (International Foundation for Telemetering, 1973-10)
    • 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.
    • 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.
    • 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.
    • 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 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 DISCRETE ADDRESS BEACON SYSTEM

      Israel, David R.; Federal Aviation Administration (International Foundation for Telemetering, 1973-10)
      The two most basic requirements for air traffic control are surveillance and communications. The surveillance system in use today is the Air Traffic Control Radar Beacon System. It is based on World War II technology and is experiencing severe difficulties as the number of aircraft carrying transponders increases. This paper outlines the present FAA program to develop a new surveillance system which will eliminate the problems, will be compatible with the existing system and will also provide a digital data-link for collision avoidance and air traffic control purposes.
    • GSFC STANDARDS PROGRAM

      Poland, William B., JR.; National Aeronautics and Space Administration (International Foundation for Telemetering, 1973-10)
    • 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.
    • 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.