• Medical Applications to Communications Satellites

      Shamaskin, Robert B.; Veterans Administration (International Foundation for Telemetering, 1978-11)
      It is recognized that closed circuit television and other electronic linkages, properly employed to deliver needed information, can be useful tools in the practice of medicine, particularly in providing linkage between distant points. In some instances terrestrial interconnection is practical, as in the case of short distances between communicating points. However, as distances become greater, so do the costs. Therefore, alternative cost effective methods of transmitting television and other types of signals for biomedical purposes are being sought. The development of high powered communications satellites demands consideration and experimentation. Therefore, the Veterans Administration is conducting a series of experiments to determine if and how communications satellites can be employed for diagnostic, therapeutic, educational and administrative purposes.
    • A Microprocessor Controlled Antenna Pointing Unit

      Kasser, J. E.; COMSAT Laboratories (International Foundation for Telemetering, 1978-11)
      Two prototype antenna pointing units (APUs) for controlling different antennas tracking geostationary satellites have been built using an 8080 microprocessor. The use of the microprocessor has allowed the same basic hardware to control two separate and different parabolic dish antennas with minimal circuitry changes and has provided significant flexibility in the performance of the units. This paper describes the APU design, which optimizes hardware and software to provide the flexibility necessary during initial testing and subsequent operation of the prototypes.
    • Microwave and Millimeter Wave Semiconductor Devices

      Fank, F. Beringer; Central Research Laboratories (International Foundation for Telemetering, 1978-11)
      Steady progress has been made this past year in nearly all microwave semiconductor technologies. Improvements in power, frequencies of operation, noise characteristics and perhaps most important at this time, reliability, have been made with GaAs FETs, GaAs Impatts, Silicon Impatts, and InP Gunn diodes. The latest state of the art as well as commercially available performance levels of each of these devices will be discussed. Both areas of microwaves and millimeter wave semiconductor devices will be covered as new millimeter wave systems requirements are pushing this technology to the forefront of development. The area of high peak powers with high average power have given an impetus to the renewed development of GaAs Impatts. Power combining techniques with these Impatts have led to replacement of medium power tubes. Present performance characteristics in single and combined technologies will be given. The expected trend for these "standard" devices over the next several years will be forecast along with a discussion of some new potential device technologies.
    • Millimeter Wave and Laser Satellite Communication System Comparison

      Goodwin, F. E.; Luke, R. T.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      Satellite communications using laser technology has received support primarily due to its high data rate potentials. However, as laser technology progresses, the system advantages of reduced size and weight relative to millimeter wave systems are becoming more apparent and realizable. A detailed comparative study was undertaken to define the merits of both millimeter wave and laser technology for a satellite communication system operating at the relatively modest data rate of 100 megabits per second. The following paper defines the communication system parameters used in the study and summarizes the results obtained for the 100 Mbps system comparison.
    • Minimum Round-Off Noise Second-Order Digital Filter with Practical Complexity Constraints

      Yao, Kung; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      It is known that, for a specified second-order digital filter transfer function, various realizations with finite precision arithmetic can yield significantly different round-off noises. For high performance communication and radar signal processing applications, the need for low round-off noise is clear. The minimum round-off noise n-th order digital filter of Mullis-Roberts generally requires (n+1)² multipliers. Most practical systems, however, desire to use a low number of multipliers. In this paper, we consider the minimum roundoff noise second-order digital filter realization under the practical complexity constraints of using only four multipliers, two delays, and four two-input adders, The optimum constraint filter has the same complexity as the know canonic direct-form realization, yet its roundoff noise can be significantly smaller for low-frequency rejection filtering applications. Some numerical results are presented.
    • MNOS Spacecraft Recorders

      Brewer, J. E.; Westinghouse Electric Corporation (International Foundation for Telemetering, 1978-11)
      MNOS memory components are well suited for use in spacecraft recorders. Recorder design considerations and MNOS chip requirements are reviewed, and projections for 10⁸ and 10⁹ bit recorders are presented.
    • Multilevel SCPC System Design

      Horstein, M.; LaFlame, D. T.; Hughes Aircraft Company (International Foundation for Telemetering, 1978-11)
      A method of assigning carrier levels in an SCPC system with mixed earth station G/Ts is developed which optimizes system performance for uniformly spaced and randomly assigned carrier frequencies. The optimum transponder backoff is shown to be identical to that for a system of uniform carriers in which the (common) earth station (G/T)⁻¹ is a weighted average of the different (G/T)⁻¹ values in the mixed system. With the transponder backoff determined, the carrier level to be transmitted to each station type is simply expressed in terms of the station G/T.
    • A Multiple FSK Microprocessor Demodulator/Decoder

      Sahmel, Rainer H.; The Aerospace Corporation (International Foundation for Telemetering, 1978-11)
      A demodulator is described that utilizes an interrupt-driven 8-bit microprocessor and an external digital counter to demodulate an 8-ary Frequency-Shift-Keyed input signal. After demodulation, the system correlates received groups of symbols with a stored code to derive and maintain character synchronization, and compute the decoded and error corrected output. The total device package count is less than 10, including the microprocessor with integral read/write memory and clock driver circuits, a Parallel Interface Adapter, a 1024 X 8-bit ROM, an 8-bit digital counter, a two-pole filter, a limiter and complete input and output buffering.
    • The NASA Standard Telemetry and Command Components (STACC)

      Eliott, Noel P.; Gonyea, Richard; Nostrand, Barbara; Orlowski, Ike; Valentine, William; Spacetac (International Foundation for Telemetering, 1978-11)
      The Standard Telemetry and Command Components (STACC) were conceived by NASA for use on the Multimission Modular Spacecraft. The components have wider application, however, and already are being considered for many other spacecraft. A programmable Central Unit controls Remote Interface Units via a full duplex data bus, providing data acquisition and command distribution capability throughout the spacecraft. The Central Unit can meet any uplink, time code, and format requirements without hardware changes. Each remote unit can acquire any type of data (serial digital, bi-level, analog, or passive analog) on any channel. A third type of unit is an optional interface providing I/O capability to an on-board computer. The protocols used on the 1Mbps data bus are compatible with MSFC's "Standard Interfaces for Digital Data, Multiplex Serial Data Acquisition and Distribution Systems (SIDD/MSDADS Standard)". The bus design saves significant harness weight and simplifies the single point ground and isolation approaches.
    • The Navstar Global Positioning System Control Segment Performance During the First Year

      Schaibly, John H.; General Dynamics (International Foundation for Telemetering, 1978-11)
      This paper reports the preliminary performance of the Navstar Global Positioning System Control Segment (CS) during the period July 1977 through July 1978. During this period, three navigation satellites were launched and were tracked and uploaded by the CS. An overview of the CS is presented as well as a summary of the present system status. User performance, total system performance, and CS performance are discussed, and methods for determining the latter are described. Performance measures including first measurement residuals and predicted pseudorange error for NTS 2 and first measurement statistics, predicted User Range Error, ephemeris prediction error, and predicted clock error for the NDS satellites are presented. The preliminary performance results presented are very good considering the early stage of multi-satellite tracking. Projecting the two satellite performance to four satellites, the CS contribution to user navigation error is 12.8-20.5 meters at 2 hours. This error consists of ephemeris and clock prediction errors of approximately 3.5 and 4.5 meters, respectively.
    • Network Monitor/Control Concept for the Western Union Satellite Switched TDMA Advanced Westar System

      Markham, R.; Sahai, K.; Schimenti, M., Jr.; Western Union (International Foundation for Telemetering, 1978-11)
      A description of the network monitor and control and TT&C concepts for the Western Union Satellite Switched TDMA Advanced Westar System is presented. The paper includes a brief description of the major system elements, their functional relationship to the network management center, and the methods to be used for monitoring/responding to station/network performance, reallocating: burst assignments, satellite switch assignments and point-to-point (multipoint) connectivity; and failure restoration of satellite communication payload service. Network monitoring and control is achieved via information exchanges between the system Network Management Center and the various system elements including: Network Earth Stations, Master Reference Stations, the White Sands TT&C Center, Western Union O&M Centers, and Western Union Administrative Center. Communication between the TMC and these facilities will be established via both satellite (8 KBPS orderwire channel) and terrestrial links. Fine/Course timing between the network earth stations and the satellite switch will be provided via reference bursts transmitted by the system Master Reference Stations into each of the four zones associated with the individual satellite channels.
    • A New Surge Protection System and a New Method of Surge Detection Using Fiber Optics

      Inagaki, M.; Miyajima, T.; Ohira, T.; Sato, Y.; Kameoka, T.; The Chuba Electric Power Co., Inc.; OKI Electric Industry Co., Ltd.; The Fujikura Cable Works, Ltd. (International Foundation for Telemetering, 1978-11)
      A new, economical protection system using fiber optics has been developed to protect existing local metallic cable systems from lightning. A field trial system was installed at a hilltop microwave relay station which is often struck by lightning. The characteristics of the system and its fiber optics were investigated using a specially developed surge detection method employing fiber optics. A direct lightning strike demonstrated that the whole system functions very successfully and provided valuable data on surges. Replacing the whole length of metallic cable with fiber cable would eliminate surge problems completely, but would be prohibitively expensive. We believe that a hybrid system presents the most economical solution. Using the system described to protect from direct surges requires the replacement of only the first few hundred meters of metallic cable. The rest of the system can be protected from induced surges by conventional means. Thus by applying this system to existing telecontrol or telecommunication cables, their reliability can be greatly increased at relatively little cost. Further, the new method of surge detection developed in relation to this system shows many advantages over previous methods, and has the potential for wide application.
    • On Overlapped Fast Fourier Transforms

      Harris, Fred; San Diego State University; Naval Ocean Systems Center (International Foundation for Telemetering, 1978-11)
      Many signal processing applications require the averaging of transforms taken over partitioned sets of data. We show that the required overlap for the partitions is window dependent and that is varies from 50% to 75% depending upon the sidelobe levels of the window.
    • On the Combined Performance of Joint Access Control/Modulation/Coding Schemes

      Rubin, Izhak; University of California, Los Angeles (International Foundation for Telemetering, 1978-11)
      The combined performance of a multi-access communication channel under joint access control/modulation/coding procedures is examined. The multi-access channel serves as a shared information transmission medium in a data communication network, such as a satellite, computer or terrestrial radio communication network. The performance of the underlying modulation/coding scheme is expressed in terms of the corresponding bit-error probability vs. signal-to-noise ratio curve. The computational cutoff error rate is also used as a proper performance measure characterizing the joint modulation/coding scheme. The performance of the underlying access-control algorithm is described by the message-delay vs. network-throughput curve. Integrating these performance functions, the combined performance of the joint access-control/modulation/coding procedure is derived. In particular, under proper bandwidth and power limitations, one can then evaluate the total amount of information that can be transmitted through the channel, in a reliable and timely fashion, at prescribed bit-error-probability and message-delay values, under various communication link, transceiver, repeater and antenna conditions.
    • Optical Antennas

      Kraemer, Arthur R.; Jones, Robert W.; GTE Sylvania Incorporated (International Foundation for Telemetering, 1978-11)
      Optical communication systems have the capability to transmit very high data rates (1-Gbps) over long distances. One primary reason is the narrow beamwidths achievable with optical antennas having diameters of less than 30 cm. This paper discusses how the Gaussian beam patterns of the laser sources are modified as they are transmitted through physically realizable optical antennas. Measurements taken on an optical antenna developed for spaceborne operation are presented and compared with theoretical predictions. Optical receiver antennas are also discussed stressing the differences between direct and heterodyne detection. Finally, consideration is given to the privacy and jamming resistance of optical communication systems using these small optical antennas.
    • Optical Fiber Thermosensor

      Ishikawa, S.; Doi, K.; Hamatsuki, T.; Nonaka, S.; Nippon Electric Co., Ltd. (International Foundation for Telemetering, 1978-11)
      An optical fiber thermosensor with bimetal has been newly developed for telemetering temperature readings at an electrically noisy place and high voltage point. Thermosensor measuring accuracy was less than 0.5 degree in the 10 to 50°C range. The device has proved to be practical and reliable.
    • Optimum Quantization for Minimum Distortion

      Caprio, James R.; Westin, Nancy; Esposito, John; Comptek Research, Inc.; State University of N.Y. at Buffalo (International Foundation for Telemetering, 1978-11)
      This paper treats the problem of optimal selection of data quantization levels for minimum error. No assumptions are made regarding the underlying statistics of the process to be quantized. A finite precursor sample of the data is analyzed to infer the underlying distribution. Selection of optimum quantization levels can then be related to the generation of an optimum histogram for the data record. The optimum histogram is obtained by a dynamic programming approach for both least mean square error and minimum Chebychev error criteria. Transmitted data can then be quantized according to levels specified by the histogram. The process can be repeated periodically either with a new data sample, if the underlying process is nonstationary, or performed on the accumulated record in the stationary case.
    • Packet Telemetry: A Possible Standard Protocol for Spacecraft Data Handling

      Greenberg, Edward; Hooke, Adrian J.; NASA Jet Propulsion Laboratory (International Foundation for Telemetering, 1978-11)
      Packetized telemetry-handling offers an opportunity to standardize major portions of the spacecraft-to-ground interface for future NASA missions. An end-to-end packet transport protocol is proposed which enables delivery of telemetry data from a remote space sensor to a ground-based user with virtually no project-unique intermediate processing. This paper reviews the possibility of creating a single telemetry format standard for both deep-space and near-earth missions. The proposed standard addresses the greatest NASA problem of the coming decade - cost - by allowing telemetry streams from many inflight spacecraft to be handled on the ground by common, simple, multimission processing elements.
    • Performance Evaluation for Shuttle/TDRSS Links Using Analytical Simulation

      Lindsey, William C.; Braun, Walter R.; LinCom Corporation (International Foundation for Telemetering, 1978-11)
      An analytical simulation package has been developed by LinCom Corporation for analytical verification of bit error rate and tracking services performance for both S- and K-band Shuttle user service through the Tracking and Data Relay Satellite System (TDRSS). The purpose of this effort was to provide a tool to assess overall system performance as well as the sensitivity to key subsystem parameters and to ensure compatibility of TDRSS and Shuttle transponder performance specifications. The evaluation is based on analytical simulation, i.e., a combination of simulation techniques and analytical performance evaluation. This allows the use of a more realistic signal format than is possible with a purely analytical approach and maintains the advantage of short computation time. The Shuttle forward and return link models and the main features of the simulation are described. Sample results of the computer runs are provided for current power budgets and system design parameters.
    • Performance Evaluation of Communication Channels by Computer Simulation

      Poza, H. B.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1978-11)
      A computer simulation model capable of aiding in the design and predicting the performance of complex end-to-end communication systems is described in this paper. The model is used to choose the optimal modulation scheme under certain communication channel constraints, define the signal distortion characteristics introduced by realizable channel components and select the demodulator/bit synchronizer designs for minimization of bit error rate. A parameter sensitivity analysis is conducted to demonstrate the usefulness of the model in evaluating the effect of different signal distortion phenomena on overall link performance.