• Data Asymmetry Analysis for Space Shuttle Communications Link

      Simon, M. K.; Tu, K.; Batson, B. H.; Jet Propulsion Lab; Lockheed Electronics Company; NASA Lyndon B. Johnson Space Center (International Foundation for Telemetering, 1978-11)
      This paper systematically analyzes the signal-to-noise ratio degradations which can potentially occur due to data asymmetry in digital transmission systems. Suitable asymmetry models are developed and error probability performance for two types of data detectors (integrate-and-dump filter, and gated-integrate-and-dump filter) is derived. Although this work was done to resolve problems being encountered in the Shuttle Kuband return link design, specifically for the 50 Mbps convolutionally encoded channel (NRZ format), generalizations are made which provide results for other cases of interest (other Ku-band return link channels, or other systems entirely). This paper therefore considers Manchester data formats (in addition to NRZ) and uncoded transmission (in addition to convolutionally coded transmission).
    • A Data Formatter and Control Unit for the SEASAT-A Synthetic Aperture Radar Ground Support Network

      Elder, B. M.; Oden, S. F.; Buchholz, D. E.; John Hopkins University (International Foundation for Telemetering, 1978-11)
      The Applied Physics Laboratory has developed special ground station equipment for NASA that recovers the video radar returns and timing reference signals from the SEASAT-A spacecraft synthetic aperture radar (SAR), digitizes the video data, and combines video and engineering data into a format compatible with a high-speed digital tape recorder. This paper describes the design and implementation of the SAR data formatter, which performs the video digitizing and data formatting functions for tape recording, and the formatter control unit, which uses stored commands from the station control center to direct operation of a special downlink demodulator during satellite passes.
    • Defense Satellite Communication System

      Donovan, Andrew R., Jr.; Def. Comm. Eng. Center (International Foundation for Telemetering, 1978-11)
      This paper will present an overview of the Defense Satellite Communication System (DSCS) with emphasis on its current capabilities and future planning. The DSCS is DoD's strategic satellite communications system providing unique and vital worldwide service to the National Command Authorities (NCAs), Worldwide Military Command and Control System (WWNCCS), the White House Communications Agency (WHCA), the Defense Communication System, NATO-Allied nations and other special users. The DSCS will soon expand to encompass the Army/Air Force Ground Mobile Forces SHF-Tactical applications and the Advanced Airborne Command Post (AABNCP).
    • Design of the DSCS III Software for Multiple Beam Antenna Control and Pattern Analysis

      Laurelli, Carmen Joseph, III; Miller, Scott F.; General Electric Company (International Foundation for Telemetering, 1978-11)
      This report describes the software capabilities developed by the General Electric Company Space Division for the real-time command, control and analysis of the multiple beam antennas (MBA) for the Defense Satellite Communication System Phase III (DSCS III). A broad description is provided which traces the generation of MBA commands by the Communications Configuration Program (CCP) through the transmission of the command data to the spacecraft and its subsequent command verification by means of telemetry data using portions of the real-time Telemetry and Command Program (TCP). A detailed description is provided of the related portions of the TCP and the CCP which are utilized to analyze requirements and generate control information for the two nineteen beam transmit MBA's and the sixty-one beam receive MBA. CCP is the key element which provides the operator the capability to merge the requirements of the user community and the MBA characteristics to provide an optimal user gain distribution. Block diagrams are employed to depict the data flow through the DSCS system and the interaction of the operator with the software. Samples of the graphic display capability of the CCP software are included to demonstrate the flexibility afforded the operator as an analysis tool for operations planning. Comparison of actual range measured antenna patterns with CCP generated patterns demonstrates the overall accuracy of simulating the receive and transmit MBA's. The CCP software is a multifaceted computer program which forms an integral part of the planning, analysis and command determination function when interfaced with the operator and analyst at the operational DSCS III ground stations.
    • Detection of Moving Optical Objects

      Burczewski, R. M.; Mohanty, N. C.; Rockwell International (International Foundation for Telemetering, 1978-11)
      This paper deals with the detection of a moving optical object in the presence of background, sensor or star and other noise. The algorithms are derived to estimate noise statistics, and its extrapolation, signal statistics, and the criterion for detecting the moving objects. The performance of the algorithm has also been derived.
    • A Distributed Microcomputer Telemetry System for Spacecraft Applications

      Lord, Donald D.; California Institute of Technology (International Foundation for Telemetering, 1978-11)
      Three significant difficulties exist in using a set of microcomputers (or any computers) as an integral part of an on-board telemetry system. The difficulties arise in providing for: a) the precise timing required by a telemetry system, including accurate time-tagging of data samples; b) the interconnection of several (many) computers in a controlled, organized, understandable manner; c) the capability to allow computer controlled science instruments to operate relatively autonomously with minimum software interactions with other computers. The three items listed above are desirable features and are achievable with proper telemetry system architecture designs. This paper will address each of the three items and present an architecture that provides the desired features.
    • A Distributed Shortest - Path Algorithm

      Humblet, Pierre A.; Massachusetts Institute of Technology (International Foundation for Telemetering, 1978-11)
      The problem of routing in a data network is often treated by assigning traffic dependent lengths to the links of the network and routing traffic from node i to node j along the shortest path from i to j . We present a distributed algorithm in which the nodes cooperate to find all shortest paths. It runs asynchronously in every node and does not require the network topology, or even the number of nodes in the network, to be known a priori by the nodes.
    • DSCS III Communications Satellite Performance

      Weinrich, A. W.; Horvath, A.; Harcar, A.; GE Space Division (International Foundation for Telemetering, 1978-11)
      The DSCS III satellite is the third generation space segment of the Defense Satellite Communication System. This satellite is unique compared to earlier DSCS satellites in that it has a six channel transponder designed for both FDMA and TDMA operation and realtime commendable uplink and downlink multibeam antennas. The antenna suit is designed to provide uplink anti-jam discrimination and selective coverage with a 61 element multibeam antenna 45 inches in diameter. The transmit antenna suit includes two 19 element multibeam antennas 28 inches in diameter that provide flexible selective coverage to maximize EIRP allocation and hence optimize satellite traffic thruput. The flexibility in antenna coverage and antenna - transponder interconnectivity allows the system operator to respond rapidly to wide variations in the deployment of forces precipitated by changing world events. This paper describes the overall DSCS III system in which the satellite functions and presents typical antennas patterns obtained with the DSCS III hardware built during the development phase of the program. In addition, overall program status is described and critical hardware elements are shown.
    • An Efficient Multichannel FFT Demodulator

      von der Embse, U. A.; Austin, M. C.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      A multichannel binary FSK demodulator for spaceborne application has been implemented using an efficient preweighted and thinned fast Fourier transform (FFT) algorithm. Theory, configuration, and performance are described and compared with the analog unit which performs the same functions. Being able to perform the first base 16 pass with add-only operations following preweighting, provided the complexity reduction which made it feasible to use the FFT to perform the channelization and predetection filtering.
    • End-To-End Information System Design at the NASA Jet Propulsion Laboratory

      Hooke, Adrian J.; NASA Jet Propulsion Laboratory (International Foundation for Telemetering, 1978-11)
      Recognizing a pressing need of the 1980's to optimize the two-way flow of information between a ground-based user and a remote space-based sensor, an end-to-end approach to the design of information systems has been adopted at the Jet Propulsion Laboratory. The objectives of this effort are to ensure that all flight projects adequately cope with information flow problems at an early stage of system design, and that cost-effective, multimission capabilities are developed when capital investments are made in supporting elements. This paper reviews the End-to-End Information System (EEIS) activity at the Laboratory, and notes the ties to the NASA End-to-End Data System program.
    • Engineering of a Multifunction Spread Spectrum System

      Winterkorn, John H.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      In the past ten years there have been dramatic strides in the spread spectrum communications system area. The knowledge of spread spectrum systems has progressed from a fragmented understanding of the techniques and their characteristics to the point where spread spectrum communication techniques are well documented and their characteristics are well understood. Thus, spread spectrum has progressed from analytical investigation into practical application. This presentation will provide a brief tutorial on spread spectrum techniques in the RF, modulation detection, and coding areas. The characteristics of these techniques will be addressed and related to specific communication functions. The presentation will address the application of spread spectrum techniques to a communication system design and will emphasize the suitability of spread spectrum for multiple applications in a given system. Specific examples of multiple spread spectrum usage will be given and a generalized approach to spread spectrum engineering will be presented. The application of this system approach to spread spectrum engineering results in spread spectrum taking on functions beyond its primary purpose of existence and becoming an integral part of a communication system rather than being an add-on, necessary but undesirable, appendage.
    • Experimental 2 GBPS MM Wave System and 4 GBPS QASK Modulator

      Horwood, D. F.; Luke, R. T.; Lee, G. E.; Des Brisay, G. S., Jr.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      A 2 GBPS QPSK modulator and demodulator were developed and BER performance was evaluated over a millimeter wave data channel. The error rate measurements taken with the breadboard equipment showed system performance to be less than 2 dB from theoretical at an error rate of 10⁻⁵. Additionally, a second QPSK modulator was constructed and combined with the first to generate 4 GBPS QASK data for future evaluation.
    • Experimental Evaluation of MSK and Offset Keyed QPSK Through Satellite Channels

      Horwood, D. F.; Angello, P. S.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      Laboratory test measurements show nearly equivalent error rate performance of MSK and OKQPSK modulation formats for channels having bandwidths approximately equal to the bit rate bandwidth and typical associated phase delay characteristics. High quality MSK and OKQPSK transmitters and a versatile modular receiver have been designed and constructed to eliminate differences associated with varying degrees of hardware quality when the performance of the various modulation formats is compared. The selection of a modulation format should, therefore, be strongly directed by considerations other than error rate, such as complexity, sensitivity to alignment, and compatibility with differential coding.
    • A Fast Complex Integer Convolution Using a Hybrid Transform

      Reed, I. S.; Truong, T. K.; University of Southern California; California Institute of Technology (International Foundation for Telemetering, 1978-11)
      In this paper it is shown that the cyclic convolution of complex values can be performed by a hybrid transform. This transform is a combination of a Winograd transform, and a fast complex integer transform developed previously by the authors. This new hybrid algorithm requires fewer multiplications than any previously known algorithm.
    • Fast Fourier Transform Algorithm Formulation

      Thong, Tran; General Electric Company (International Foundation for Telemetering, 1978-11)
      A new unified formulation of the fast Fourier transform based on the unwrapping of a multi-dimensional array is presented. The decimation in time FFT algorithms is treated in detail. The decimation in frequency algorithms is then discussed.
    • FET Amplifiers for Communications Applications

      Kennedy, W. Keith, Jr.; Watkins-Johnson Company (International Foundation for Telemetering, 1978-11)
      The Field Effect Transistor (FET) is revolutionizing microwave communications with both its low noise performance and high dynamic range. This paper emphasizes developed amplifier hardware available today for both ground and satellite applications. The focus is on the noise figures and output powers available from 4 to 15 GHz.
    • Fiber Optic Sensors for Military, Industrial and Commercial Applications

      James, K. A.; Quick, W. H.; Strahan, V. H.; Rockwell International Corporation (International Foundation for Telemetering, 1978-11)
      This paper presents concepts for fiber optic sensors. Such sensors have many inherent advantages over conventional sensors - including digital format and noise immunity. Four examples of specific sensor system designs are discussed - each of which demonstrates a different optical modulation format. The birefringent temperature transducer illustrates direct digital signal modulation. The temperature/pressure dependent semiconductor filter illustrates high-pass optical wavelength signal encoding, while the coupled polarized-mode transducer shows how a solid-state sensor can produce narrow-bandpass optical-wavelength signal encoding. Finally, the luminescent temperature sensor illustrates a manner in which a solid-state sensor can be constructed to produce pulse-width modulation of an optical signal. The potential for fiber-optics sensors adds one more facet to the growing fiber optics market.
    • A Flexible User Oriented Approach to Communications Systems Simulation

      Fashano, M.; Austin, M. C.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      An advanced software/hardware computer system developed for the simulation of communications systems is described. This user oriented system allows for flexible and efficient modeling and simulation of complex communications systems. Excellent agreement between simulation and measured results has consistently valididated the simulation approach.
    • Future Automated Spacecraft as an End-to-End System Element

      Bird, Thomas H.; NASA - Jet Propulsion Laboratory (International Foundation for Telemetering, 1978-11)
      Concepts for a highly automated spacecraft, which is much more independent of ground operations than current spacecraft, have been investigated. Applicable systems and technology requirements are identified for maximum onboard automation of mission functions. A spacecraft concept which requires infrequent ground contact while increasing mission effectiveness is described. The potential impact of such a system on end-to-end system design is discussed.
    • GDSC Aerospace Test System (ATS)

      Layton, J.; Schiano, C.; Grumman Data Systems Corp. (International Foundation for Telemetering, 1978-11)
      Grumman Data Systems Corporation (GDSC) is presently developing another in a series of computerized realtime systems which accepts, preprocesses, analyzes and displays telemetry and range data. This new Aerospace Test System (ATS) will first be utilized by the Navy at the Pacific Missile Test Center (PMTC). The computerized test system will analyze data, in realtime, being telemetered from missiles, aircrafts and satellities. The system will accept, decommutate/demodulate, preprocess, analyze and display data being transmitted in the forms of PCM, PDM, PAM, and FM. The system will allow test personnel to continually monitor, in realtime, critical raw and calculated parameters. The answers provided to test personnel, in one phase of the mission, will give them the ability to proceed into the next with a high degree of confidence. The vast amounts of data acceptable by the system, together with its analytical and display capabilities will allow test personnel to accomplish several tests during a single time frame. The system will also allow test personnel to be in complete control of their mission via the data uplink capability. It is a system that support Batch, Time Share, and Remote job entry processing concurrently. Utilized properly, it can greatly reduce the quantity and increase the quality of batch processing.