• A High Data Rate Recorder/Reproducer

      Brobst, R. E.; Odetics, Inc. (International Foundation for Telemetering, 1977-10)
      A High Data Rate Recorder (HDRR) has been developed under contract with Engins Matra, France, to be used in the European Spacelab. Engins Matra is responsible for the design and testing of the Command and Data Management System (CDMS). The HDRR is part of the CDMS which performs on-board data processing, multiplexing and storage. The Spacelab is a primary payload of the U. S. Space Shuttle Orbiter. The HDRR interfaces with the Spacelab High Rate Multiplexer, which, in turn, provides the inputs to the Tracking Data Relay Satellite (TDRS) down-link system for transmission to the ground. The HDRR is capable of recording and reproducing at a maximum rate of 32 Mb/s. The total continuous record time allowed at this rate is 20 minutes. Thus a total of 3.84 x 10¹⁰ bits can be stored. The HDRR has a versatile command and data interface that allows for recording at any rate between 1 Mb/s and 32 Mb/s. Reproduction can be performed at 2 Mb/s, 4 Mb/s, and any rate between 8 and 32 Mb/s.
    • Underwater Optical Beam Tracking

      Gagliardi, R. M.; University of Southern California (International Foundation for Telemetering, 1977-10)
      The use of blue-green laser frequencies for establishing an air ocean underwater communication channel has been well accepted. However any attempt to initialize or maintain such a link will invariably require some method of accurately spatially pointing and tracking the penetrating beam. In this paper we present results of a study concerned with determining the ability to spatially track an optical after undergoing underwater propagation. By invoking the concept of modulation transfer theory and substituting established propagation models for underwater coherence functions, the focal plane intensity patterns generated in wide angle optical lensing systems can be determined, as a function of the link characteristics (e.g. sea state, depth into the ocean, turbulence, etc.).With the intensity pattern modeled, the behavior of various forms of optical trackers can be analyzed by the application of standard tracking loop theory. Of particular interest here is the application of well known mathematical tools, such as Kolmogorov theory, which allows generalized statistical analysis to be performed on both linear and nonlinear dynamical systems. The result of such an approach is the development of a differential equation whose solution yields the statistics of the tracking error. Theoretical studies of this type have been examined previously for generalized scattered optical fields [1]. With these basic approaches as a guide, mean squared tracking errors can be derived, which assesses the perfomance of the beam tracker in relation to the channel characteristics.
    • A Satellite Automatic Control System

      Bleiweis, J. J.; Redman, P. C.; COMSAT Laboratories (International Foundation for Telemetering, 1977-10)
      The primary task of existing satellite control centers is to automatically monitor the operational performance of existing satellites and to manually generate control commands so that these satellites remain within specified operational limits. This paper describes some basic characteristics of an existing satellite control center and identifies a method that may be employed to gradually introduce automatic commanding to the facility. Candidate methods of automatic commanding are described.
    • Results of a Q-M/PSK Data Modem Performing in a Hybrid, Voice and Data Mode, Through the ATS-6 Satellite

      Golab, Joseph; Duncombe, Christopher; Bland, Robert G.; U. S. Department of Transportation (International Foundation for Telemetering, 1977-10)
      The Transportation Systems Center (TSC), under the sponsorship of the FAA, has been involved in the development of advanced voice/data multiplexed modems applicable to ground-aircraft communications via satellite in support of the AEROSAT program. TSC was assisted by the Canadian Ministry of Transport (MOT), Communications Research Center (CRC), in the planning and conducting of recent flight test experiments using the NASA ATS-6 satellite.
    • Design Concepts for a Highly Reliable Multimicroprocessor System for Communication Satellites

      Plisson, Francois; MATRA S. A. (International Foundation for Telemetering, 1977-10)
      Over past years, the microprocessors have been used widely and efficiently for many applications. Some of them have become industrial standards, and the question arised how to use them most efficiently for space applications. The paper describes the design concepts which have directed the study and the breadboarding of a trimicroprocessor system and its monitoring software. These concepts have been traded off for reaching a high system overall availability and flexibility. The multiprocessor is organized around C-MOS microprocessors and a time shared/common bus, designed for reliable operations. The monitoring software is especially developed to yield a triple redundancy for critical (i.e. mission success dependent) software functions and to assure the mutual failure independency of the application programs. On board telecommunication satellites, the multiprocessor structure have been found better suited for reliability, probability of mission interruptions and its capability of degraded operation when it was compared to a classical stand by redundant monoprocessor array. At the end of the year, the triprocessor system will be integrated into a satellite attitude control simulator for a system closed-loop test with an air bearing table and actual satellite equipments.
    • Pseudo-Random Code Sidelobe Canceller

      Haber, Conrad H.; Nossen, Edward J.; Government Communications Systems RCA (International Foundation for Telemetering, 1977-10)
      During acquisition of direct sequence pseudo-noise signals, time sidelobes are produced at the correlator output which will degrade detection performance. These sidelobes may be the result of additive noise, channel distortions, deliberate jamming or the non-ideal correlation function of truncated code sequences. In order to minimize these sidelobes, special codes can be selected based on their low sidelobe levels, or some special sidelobe reduction or cancellation algorithm may be devised. A sidelobe cancellation algorithm for use with LSI correlators has been simulated. Segments of a maximum length code word as well as a totally random bit stream were tested. The simulation results show that the largest sidelobes are reduced by a small amount; however, the majority of the sidelobes are reduced by as much as 6 dB. Consequently the false alarm rate for a particular threshold setting may be reduced. A compatible technique for the derivation of a CFAR reference from the same correlator was also successfully simulated.
    • The Development of a Satellite On-Board Microcomputer

      Eardley, Deryck W.; British Aircraft Corporation (International Foundation for Telemetering, 1977-10)
      The paper describes a miniaturized computer for space use that is being developed under a contract from Intelsat. An all CMOS design is used with the corresponding low power and high speed associated with CMOS. Extensive use is made of LSI and the computer is based on the Intersil or Harris 6100 microprocessor. This has the same architecture as the PDP8-E and the extensive range of DEC PDP8-E software can be used. Provision has been made for both serial and parallel input/output ports. A development prototype is described that has serial and parallel ports. The associated memory is expansible up to 32K words in 2K blocks. RAM or PROM can be used or interchanged in blocks of 256 words. A programmable timer is included for real time applications. A bench model of the computer is also described which is made for program development. It is not to the same environmental standards as the development prototype but has the same facilities together with a control panel and provision for a teletype. The use of the Bench Model for software development is described.
    • An Integrated Error Correcting/Pseudo Random Communication System

      Schiff, Maurice L.; ITT Aerospace Optical Division (International Foundation for Telemetering, 1977-10)
      This paper describes a pseudo random (PN) communication system with an integral error correcting code. The error codes are again based on maximal length sequences and simultaneously provide coding gain with bandwidth expansion. A basic modem starting at 2400 bps data rate and expanded to a 5 Mbps chip rate is described. Theoretical and hardware test results are presented to verify the concepts. Finally, synchronization of this system is discussed. A PN range extension concept is developed which improves the acquisition time with only a trivial increase in system complexity.
    • Processing Radiation Data on Board TIROS-N Satellite

      Wisniewski, J. H.; Ford Aerospace & Communications Corp. (International Foundation for Telemetering, 1977-10)
      The function of the data processing unit (DPU) as part of a space environment monitor subsystem is described, with emphasis on special features in the data handling process. Important design goals for achieving DPU performance are outlined. Design implementation to achieve these goals is discussed. Some of the more complex circuits are described in detail as examples of onboard data processing. The packaging approach for effecting savings in weight and power is also presented.
    • Comparison of Analog and Digital Transmissions for Multichannel Voice

      Birch, J. Neil; Office of the Secretary of Defense (International Foundation for Telemetering, 1977-10)
    • NASA Teleconferencing Pilot Project (An Evaluation of Teleconferencing as a Substitute for Travel)

      Fordyce, Samuel W.; NASA (International Foundation for Telemetering, 1977-10)
      NASA conducted a Pilot Project during 1975 and 1976 to determine the extent that teleconferencing could replace travel to meetings. The network consists of approximately 34 teleconference rooms and 50 fast facsimile machines, all interconnected on private lines to a master switchboard in Huntsville, Alabama. In addition, portable conference telephones augmented the voice network, and experimental video teleconferences were tried. Evaluations show that the teleconferences "saved" travel costs approximating 21% of the travel budget at a communications cost of 3% of this budget. The unused travel funds were diverted into travel other than to management meetings, and consequently, coordination may have improved. This paper discusses the operation of the Pilot Project, which has matured into an operational teleconference network. This experience may be of value to other organizations wishing to adopt teleconferencing.
    • A-M/AGC Weighted Pre-Detection Diversity Combining

      Hill, E. R.; Pacific Missile Test Center (International Foundation for Telemetering, 1977-10)
      A method has been proposed for improving the performance of automatic gain control (agc) weighted diversity combiners in the presence of fast fading radiofrequency (rf) signals by use of the amplitude modulation (a-m)(detected linear intermediate-frequency (i-f) envelope) in addition to the agc voltage to weight the combiner. Also suggested was a method for selecting the channel with the best signal-tonoise ratio (SNR) by use of the a-m and agc voltages. Experimental hardware has been constructed for evaluation of three configurations: an a-m/agc weighted combiner; an a-m/agc based selector; and an a-m/agc combiner/selector where the criterion for combine or select is determined by the phase error between the two channels. An experimental study was also conducted of the phase-locked loop (PLL) to determine the best configuration and parameter values for the combiner application (where relatively large phase errors are permissible). Data were taken under laboratory and operational (Vandenberg Air Force Base) conditions and are compared with data taken with a commercial agc weighted combiner.
    • A Data Acquisition System Featuring On-Board Processing

      Endsley, Neil H.; Lee, Kyong H.; Maschhoff, Robert H.; Gulton Industries Inc./DSD (International Foundation for Telemetering, 1977-10)
      A data acquisition system for the telemetry data on the Technology Development Vehicle (TDV) program is presented. To meet the major experimental objectives of the TDV mission - the collection of high frequency vibration and acoustic data on a re-entry vehicle - required some unusual design approaches. It is shown that collection of this data requires a great deal of data compression. This was accomplished using a technique of on-board data processing - actually performing the first step of data reduction in flight. The entire data acquisition system is described in light of the requirements imposed by the data with emphasis on unusual problems and solutions. Results of ground tests in an anechoic chamber are presented, and a brief discussion of the errors involved in onboard processing is given.
    • Modeling of Optical Propagation in the Underwater Environment

      Karp, Cherman; Naval Ocean Systems Center (International Foundation for Telemetering, 1977-10)
    • Experimental Comparison of Pulse Code Modulation Codes for Magnetic Recording

      Law, E. L.; Pacific Missile Test Center (International Foundation for Telemetering, 1977-10)
      The bit error probability (BEP) versus signal-to-noise ratio (SNR) was experimentally determined for Non-Return-to-Zero-Level (NRZ-L), Bi-Phase-Level (BIΦ/-L), Delay Modulation (DM) and Miller Squared (M²) codes for a bandpass channel. This was done by passing the data through a 400 Hz to 500 kHz Bessel bandpass filter and linearly adding noise. The power spectral density of the noise was shaped to match the noise out of an analog magnetic tape recorder running at 30 inches per second (in./s). This provided a simulation of an optimum wideband 2.0 MHz tape recorder running at 30 in./s (no flutter, tape dropouts, etc.). The bit rate, pattern, and code to be tested were then selected. The SNR was varied until the bit error probability was approximately 10⁻⁶ With a commercial Pulse Code Modulation (PCM) bit synchronizer with a "good" dc restorer and a pseudo-random pattern at 1.0 megabits per second (Mb/s) (33.3 kilobits per inch (kb/in.) equivalent packing density), NRZ-L had a 4 dB SNR advantage over DM and a 14 dB advantage over BIΦ/-L for a BEP of 10⁻⁶ through the bandpass channel. At 1.5 Mb/s, NRZL had a 6 dB advantage over DM and a 10⁻⁶ BEP was not achievable with BIΦ/-L coding. For a synchronizer with no dc restoration NRZ-L had only a 1 dB advantage over DM at 1.0 Mb/s and also only a 1 dB advantage at 1.5 Mb/s. M² gave the same results as DM for pseudo-random data. However, M² was relatively insensitive to patterns while DM and NRZ-L required a higher SNR with a "good" dc restorer and lost synchronization completely with no dc restorer for worst case 16-bit repeating patterns.
    • International Telemetering Conference Proceedings, Volume 13 (1977)

      International Foundation for Telemetering, 1977-10
    • NASA Standard 4 x 10⁹ Bit Spacecraft Tape Recorder

      Welch, James P.; Odetics, Inc. (International Foundation for Telemetering, 1977-10)
      The concept of employing standard spaceborne hardware to meet the needs of present and future spaceborne missions is the beginning of a new era. In this paper, attention is focused on describing the functional characteristics of a 4 x 10⁹ bit magnetic tape recorder that will become the standard tape recorder for future satellite missions. The recorder development was directed by NASA Goddard Space Flight Center.
    • ACMR/I System

      Parker, J.; Cubic Corp. (International Foundation for Telemetering, 1977-10)
      The instrumentation system described provides real-time attitude and position data on 8 high-dynamic fighter aircraft and position data on 12 additional cooperative targets. Position data is derived from multilateration range measurements using FM-CW phasecomparison techniques. Attitude and acceleration data is obtained from a strap-down inertial system initialized by the ranging system. Digital data is transmitted to and from the target by frequency shift keying of the ranging carrier. A multiprocessor ground computer using Kalman filter techniques provides a total state vector for each participant at a rate of 10 per second. The multiprocessor also provides real-time missile simulation for performance scoring. The Display and Debriefing Subsystem provides real-time computer-drawn pseudo three-dimensional display of the aircraft, total replay capability, and control of the entire system from the operator's console.
    • Quadrature Modulation Hybrid Voice and Data Modem

      Lerner, Theodore; Lerner Technology Inc. (International Foundation for Telemetering, 1977-10)
      The Quadrature Modulation Hybrid Modem is a new system designed to provide voice only, data only, or combined voice and data communication. It provides good voice intelligibility at low values of C/N0 by making use of a quadrature modulation technique which permits essentially nonthresholding demodulation of the voice signal. Power sharing between voice and data signals can be easily changed to accommodate different requirements. Intelligibility tests have been performed and indicate an intelligibility of 90% in the voice-only modem at a value of C/N₀ of 43 dB-Hz, and an intelligibility of 80% in the combined voice and data mode at a value of C/N₀ of 43 dB-Hz with an error rate for data of 10⁻⁵.
    • Adaptive Array Control Concepts for TDRSS

      DuPree, J. E.; TRW Systems (International Foundation for Telemetering, 1977-10)
      The Tracking and Data Relay Satellite System (TDRSS) will use an Adaptive Ground Instrumented Phased Array(AGIPA) system for remote beamforming and tracking of low-orbit user spacecraft. This paper introduces the control concepts involved in its beamforming, tracking, and calibration. These concepts are related to the Kalman filter. Several suboptimal, but attractive, tradeoff options are discussed.