• Random Coding Bounds for Noncoherent mFSK Multiple-Access Channels

      Omura, Jim K.; University of California, Los Angeles (International Foundation for Telemetering, 1979-11)
      We investigate a time-varying trellis coded multiple-access scheme using noncoherent mFSK signals. Techniques similar to this were originally proposed by Cohen, Heller, and Viterbi and more recently in a mFSK form by Viterbi. In these multiple-access systems van der Muelen Ahlswede Liao, Gaarder and Wolf , Kasami and Lin, Weldon and Wolf have shown that the decoded symbols of one user can be used to reduce the "multiple-access noise" to other users and thus allow for a larger achievable rate region than one would expect with conventional time division multiple-access techniques. In some cases, specific codes were investigated. Peterson and Costello and Chevillat have extended these earlier works to convolutional and trellis codes. In this case the decoder is designed as a "super" Viterbi decoder that regards all transmitter trellis codes combined to form a single "super" trellis encoder. In this paper we investigate the noncoherent mFSK scheme discussed by Viterbi and generalize to single level and multi-level energy detectors with a single "super" Viterbi decoder at the receiver. The main results are random coding bounds for the general case where L users each have remotely located time-varying trellis encoders of constraint length K. We assume throughout that the channel is noiseless, and symbol timing synchronization is maintained among the L users. These assumptions are being relaxed in the thesis research of Sorace.
    • Managing the SPS Antenna Power Beam Performance

      Dickinson, Richard M.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1979-11)
      The proposed satellite power system for importing nearly continuous solar-electric power from synchronous orbit, is to consist of a fleet of orbiting solar collector spacecraft, each of approximately 100 km² area. The 6.25 GWe power output is converted to 2.45 GHz microwaves and beamed to earth based rectenna collectors for conversion to high voltage ac or dc power, to feed into the electric utility transmission grid.
    • Active Retrodirective Array for Microwave Power Transmission

      Chernoff, Ralph C.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1979-11)
      An active retrodirective array (ARA) is a phased antenna array in which retrodirectivity of the transmitted beam is produced by electronically conjugating the phase of the pilot signal received by each element of the ARA. ARA's can be easily modified to function as receiving, as well as transmitting, arrays. Due to their inherent failsafe characteristics, ARA's are particularly attractive for microwave power transmission from solar power satellites. Communication satellites and deep space probes are other possible applications. The "Central phasing" principle, in itself a simple generalization of the phase conjugation principle, avoids the need for structural rigidity implicit in conventional phase reference distribution systems. We describe a phase reference "tree" for implementing central phasing in very large ARA's, as well as a new kind of "exact" frequency translating phase conjugator which provides both input-output isolation and freedom from squint. The effects of doppler, aberration, impedance mismatches and multipath are discussed. We report on the performance of an experimental two element ARA, and on the design of an eight element ARA now being built at JPL.
    • A Proposed Time Code Standard for Telemetry and Space Applications

      Chi, Andrew R.; Goddard Space Flight Center (International Foundation for Telemetering, 1979-11)
      A computer oriented time code designed for users with various timing requirements is proposed. Its format meets with the packet data format requirement of the new data handling and management concept, known as the NASA End-to-End Data System (NEEDS). It is equally applicable to spacecraft and ground users. The time code is arranged in parallel groups of binary numbers containing day, second, millisecond, microsecond, and nanosecond resolutions. The day count system is a four digit number truncated from Julian day numbers known as Truncated Julian Day (TJD). It has a repetition period of 27.379 years. Four options of resolutions in seconds, milliseconds, microseconds, and nanoseconds are offered. They are formatted in 4, 6, 7, and 8, eight-bit Byte words, respectively. To identify each resolution option of the time code, a variable prefix code consisting of 1 to 3 bits is used. This paper will present in detail the time code and its applications.
    • Appendix: Eighteenth Annual Report of the Telemetering Standards Coordination Committee

      Pizzuti, Michael (International Foundation for Telemetering, 1979-11)
    • TDMA Satellite Onboard Switching Center Electronics

      Kasser, Joe; COMSAT Laboratories (International Foundation for Telemetering, 1979-11)
      The introduction of TDMA into satellite communications links increases the complexity of satellite onboard communications path routing circuitry. This paper discusses two different design approaches to the control electronics of an onboard TDMA satellite switching center. One approach uses custom large-scale integrated (LSI) circuitry; the other is microprocessor based. The two designs are compared, and an optimal hardware configuration is developed.
    • System Design for Nd:YAG Laser Communications

      Wolf, John D.; Pautler, James A.; Olshaw, Robert Z.; Eastwood, Lester F., Jr.; McDonnell Douglas Astronautics Company; McDonnell Douglas Corporation (International Foundation for Telemetering, 1979-11)
      This paper describes key design issues and tradeoffs in Nd:YAG laser communications system design. As background, it reviews missions and applications contemplated for Nd:YAG technology. It also briefly summarizes receiver operation, focusing on the primary beamsteering functions that enable accurate pointing of the very narrow communications beam (5 μrad for a one gigabit per second link). The remainder of the paper considers Nd:YAG lasercom system design methods. The paper reviews typical system specifications (e.g. data rate, margin, and acquisition time) and constraints (such as platform dynamics and laser capabilities). It shows how the designer makes tradeoffs among tracking accuracy, control bandwidths, fields of view, signal to noise ratio and transmitted beamwidth to iterate to a final choice of design parameters, and it describes examples of resulting designs.
    • NASA Standard Experiment Command and Data System for Shuttle/Spacelab Payloads

      Kasulka, Larry H.; Wilkinson, Darrell D.; Mcdonnell Douglas Astronautics Company (International Foundation for Telemetering, 1979-11)
      A new equipment command and data system (CDS), being developed by NASA for Shuttle/Spacelab-payload users, takes advantage of the more liberal constraints being offered a Shuttle payload user (i.e., size, weight, and power) to save cost. This Spacelab Payload Standard Modular Electronics (SPSME) system provides an extremely flexible approach derived from the modular design of the CAMAC system. SPSME promises to provide a real cost savings to the space community due to its universal application to most Spacelab experiments. NASA projections based on the mission model for the first 19 Spacelabs using SPSME versus the historical hardware results in approximately $125.4 million savings.
    • Microprocessor-Based Analog Voice Scrambling Techniques

      Udalov, Sergei; Axiomatix (International Foundation for Telemetering, 1979-11)
      Analog voice privacy techniques provide the advantage of being compatible with the 3 kHz audio bandwidth of the existing radio and telephone channels. The degree of privacy provided by an analog voice scrambling technique, however, is proportional to the number of time and frequency elements into which the voice signal can be divided as well as to the number of permutation patterns according to which the elements are scrambled. This implies the requirement for a high degree of signal-processing capability. Microprocessorbased implementations of an analog voice scrambling device provide a large potential for signal processing and scrambling. Furthermore, they provide this potential at a reasonable cost, small volume and moderate power consumption. In addition, a single microprocessorbased analog voice privacy device can be configured in software to yield various degrees of privacy, depending on a particular use and circumstances. Also, a variety of auxiliary functions such as timing, code generation, synchronization and analog-to-digital conversion can be time-shared within the same microprocessor chip, thus minimizing the requirement for support hardware. The purpose of this paper is twofold: (1) to provide an overview of the existing analog voice privacy techniques, and (2) to specifically outline the capabilities of the microprocessor-based analog voice privacy system design, with a particular emphasis on achieving an analog scrambled signal compatible with the 3 kHz nominal audio bandwidth of the existing radio and telephone channels. Also, workable algorithms used for microprocessor-based analog voice scrambling in frequency as well as in time domain are described. Tape recordings of the voice scrambled and recovered with these algorithms are presented for comparison.
    • Satellite Control System

      Baker, J.; Vest, S.; Gilcrest, A. S.; Rodriguez, T. M.; Air Force Systems Command; The Aerospace Corporation (International Foundation for Telemetering, 1979-11)
      The motivations are discussed for considering a dedicated military satellite system that will provide tracking, telemetry, and command (TT&C) services, wideband mission data relay to the continental United States (CONUS), and narrowband mission data relay on a worldwide basis for United States Air Force (USAF) satellite systems. Mission models for the next 20 years are discussed. A concept study is in progress, and the guidelines for this effort are presented.
    • Space Shuttle Payloads Support Capability

      Torres, Frank; Rockwell International (International Foundation for Telemetering, 1979-11)
      The NASA/Rockwell Space Shuttle with its highly versatile avionics and electrical provisions for use by the Shuttle payloads will provide an efficient system for future national space program activities and space program activities from foreign countries. This paper summarizes the avionics and electrical payload capabilities and interface characteristics. It includes a description of the command and data systems interface, the caution and warning system interface, and the aft flight deck accommodations; the electrical power distribution system; and the standard mixed cargo harness.
    • The Design of CO₂ Laser Communication Systems

      Einhorn, Arthur J.; Hughes Aircraft Company (International Foundation for Telemetering, 1979-11)
      Future demands for more information transfer in space will increase the demand for wider space communications with narrower beamwidths. Both of these requirements suggest using as high a carrier frequency as possible. The wider bandwidth is necessary to increase the information carrying capacity. The narrower beam allows the use of a smaller amount of transmitter power to a distant receiver and concomittenly results in larger antenna gains. The Carbon dioxide (CO₂) laser system meets many requirements for a space qualifiable space communication such as wideband modulation capability, potentially long life and reliability. In this paper we discuss several aspects of the design of a CO₂ laser communication system for space application in terms of overall functional requirements, system tradeoffs and subsystem component selection. The results require use of state-of-the-art components which are or can be space qualified.
    • Management of Software Development

      Downs, H. Robert; Science Applications, Inc. (International Foundation for Telemetering, 1979-11)
      Development of software is well known as a very difficult management problem. When the software is a part of a complex telemetry system, the management problem becomes particularly complex; particularly if the software is not well defined before implementation begins. This paper discusses some of the problem areas in software management with particular emphasis on the requirements and design stages. In a telemetry system development effort, the system designers must decompose system requirements into requirements on various subsystems. This process is particularly apt to lead to software requirements which are not well defined, impossible to meet or inappropriate for the hardware on which it is implemented. This paper addresses methods of performing and managing this type of software development.
    • A Review of the Public Broadcast Service TV Distribution System and Plans for the National Public Radio System

      Kellow, Robert S.; Rockwell International (International Foundation for Telemetering, 1979-11)
      Nationwide Television Programming for the Public Broadcasting Service is now being carried by the largest integrated network of Earth Stations ever constructed by a single turn-key contractor. The 165 station network, including 5 remote origination transmit terminals, was completed significantly ahead of a schedule established two years before. Such an accomplishment required carefully orchestrated efforts between customer and contractor in the areas of system and equipment design and qualification, site selection and design, frequency coordination, equipment scheduling, on site construction, site installation and test effort mobilization. Unusual and unexpected constraints were often encountered, requiring resourceful and innovative solutions. Performance records since early 1978 when initial operations began indicate the reliability, availability and cost improvement goals of the system have been exceeded by a significant margin. A similar system for the National Public Radio, involving 205 stations (15 with transmit capability) is currently in the early stages of implementation.
    • Decentralized Control for Large Communication Satellites by Model Error Sensitivity Suppression

      Sesak, John R.; Bowman, Robert M.; General Dynamics Convair Division (International Foundation for Telemetering, 1979-11)
      The rapid growth in world demand for satellite telecommunications and the limited number of positions in the geostationary arc are leading inexorably to larger, higher capacity communications satellites. This trend, coupled with the projected weight and volume capability of the Space Transportation System (STS), will lead to satellites in the 80s weighing 5000 kg and measuring 50 to 100 feet across. By the end of the century these figures could increase again by an order of magnitude. Such large, low-density structures tend to have closely spaced, low-frequency dynamic modes. At the same time, multibeam-frequency reuse antennas (MBFRA) projecting narrow-spotbearns require pointing stability within a hundredth of a degree or so. The combination of low structural natural frequency and more stringent pointing requirements imposes the need for an entirely fresh approach to dynamic control of communications satellites. This paper outlines such an approach. A modern optimal control methodology is advanced that provides decentralized modular control for large communication satellites. The fundamental property of the control algorithm is its ability to stabilize certain subsets of vibration modes without disturbing others. This decoupling action allows the control task to be implemented in a modular or building block fashion so that different modal subsets are stabilized by separate controllers. Decentralization according to functional task is also possible such that noninteracting rigid body and elastic body control is achieved. Thus, the technique provides a solution for the problem of rigid body control in the presence of low frequency elastic modes that are in the rigid body controller bandwidth. The design methodology, termed Model Error Sensitivity Suppression (MESS), is a derivative of modern optimal control and estimation theory. Several examples illustrate the capability of the design algorithm.
    • Convolutional Error Detection on an Additive White Gaussian Noise Channel

      King, Maurice A., Jr.; The Aerospace Corporation (International Foundation for Telemetering, 1979-11)
      Concatenated coding schemes involving a convolutional inner code and a block outer code have occasionally been used in communication systems that are very intolerant of errors. In these schemes the vast majority of channel errors are corrected by the convolutional decoder while the block outer code is used to detect convolutional decoder errors. Block code words containing detected errors are erased. Soft decision Viterbi convolutional decoders operate by comparing path metrics and selecting the path with the largest metric (the maximum likelihood path). There is a substantial amount of information in the path metrics that is not used in this pick-thelargest decision. It is proposed that some of this information be used in a probabilistic decoding error detection scheme. Such a detection scheme would obviate the use of the block outer code. The result is a bandwidth savings at the cost of some additional processing of the convolutional code metrics.
    • Telecommunications for the International Solar Polar Mission

      Chan, Richard J.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1979-11)
      The International Solar Polar Mission (ISPM) is a joint venture of the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) for each to develop a single spacecraft to carry unique scientific experiment hardware packages. The hardware is designed to gather data for the scientific study of solar properties and interplanetary physics out of the ecliptic plane.
    • An Overview of TDRSS Ground Station

      Morran, Peter C.; Bebb, Joan E.; TRW DSSG (International Foundation for Telemetering, 1979-11)
    • Dual Beam Single Axis Tracking Antenna for Tracking Telemetry Instrumented Airborne Vehicles

      Sullivan, Arthur; Electra Magnetic Processes, Inc. (International Foundation for Telemetering, 1979-11)
      A dual-beam, single-axis, tracking antenna capable of receiving and tracking telemetry data from an instrumented airborne vehicle is described. The dual-beam, single-axis, tracking antenna system consists of both a high-gain and a low-gain antenna positioned by the same antenna pedestal/servo electronics. Automatic switching between the high-gain and the low-gain antennas, based on received signal strength, permits tracking from maximum range (using the high-gain antenna) to close-in nearly overhead passes (using the low-gain antenna) by exploiting the wide-beam characteristics of the low-gain antenna when space losses are at a minimum. The wide beamwidth of the low-gain antenna permits its use as an acquisition aid for the high-gain antenna during initial acquisition, while its wide beamwidth also precludes locking on to a side lobe. The use of only one tracking axis rather than two reduces cost and improves reliability.
    • A Microcomputer Interface for Transfer of Data Between Multiple Computer Systems

      Smith, B. L.; Vandenberg Air Force Base (International Foundation for Telemetering, 1979-11)
      An interface was required for transmitting telemetered inertial guidance data from any one of twelve SEL 32/55 computers to an IBM 360-65 and a CDC 3300 computer. A flexible interface was designed to meet this requirement. The interface is comprised of several nested microcomputer systems and a fiber optic data transmission system for accomplishing the control and data transmission functions. A unique approach was used to transmit the data asynchronously and make it appear to be synchronous at the response of the computers receiving the data. A description of the approach and system operation will be discussed.