• 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.
    • Performance Evaluation of Step Stare Sensor for Space-Based Air Vehicle Detection

      Ho, C. Q.; Rockwell International (International Foundation for Telemetering, 1978-11)
      Detection of aircraft by a space-based infrared sensor is a demanding task using near-term technology. To achieve sufficient sensitivity, background noise suppression is required because of the relatively weak target signal. Background noise suppression techniques, first order, second order, and higher order temporal differencing, spatial and temporal differencing, are analyzed and compared. Background noise due to both background drift and system vibration effects are calculated. Pixel-to-Pixel offset-induced background noise leakage is also evaluated.
    • Performance of Bandlimited and Hardlimited PSK Signals

      Rey, R. D.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1978-11)
      Transmission of a signal through a channel, such as a satellite communication channel, results in distortion of the signal due to bandlimiting in the individual channels and hardlimiting. The purpose of this paper is to study the effects that channel distortion due to filtering and hardlimiting have on the performance of BPSK and QPSK. The results will be used to determine the maximum bit rate which can be transmitted through a channel having a particular bandwidth with a specified limit in degradation of performance.
    • Performances of Regenerative and Nonregenerative Satellite Repeaters with MPSK Signalling

      Woo, K. T.; California Institute of Technology (International Foundation for Telemetering, 1978-11)
      Linear (translation), hard-limited, and demod/remod types of satellite repeaters are considered in this paper. Both uncoded and coded multiple phase shift keyed (MPSK) signals are assumed to be transmitted through these repeaters. Relative performances of these repeaters in the presence of uplink and downlink noises are then compared quantitively. Probabilities of bit errors and the computational cutoff rates are computed for 2, 4, and 8 phases PSK signals, with uplink and downlink SNR's as parameters.
    • Phase Referencing for MA Demultiplexing in the TDRSS

      Gagliardi, R. M.; University of Southern California (International Foundation for Telemetering, 1978-11)
      The TDRSS performance is based, to a large extent, on the ability to maintain phase coherency between user, satellite, and ground segment. This is especially true for the MA return subsystem, which uses coherent referencing for multiplexing and demultiplexing between the TDRS and ground processor. Phase noise appearing on these referencing waveforms destroy the phase coherency, and will degrade the overall MA return operation. In this paper the manner in which this phase referencing is achieved is described. In addition, the results of a preliminary study to distinguish the key MA return phase noise sources, and the manner in which each will ultimately influence performance, is presented. The results show that the return phase noise effects can be separated into "coherent" and "noncoherent" contributions, and each must be separately evaluated. The effect of the various tracking loop bandwidths throughout the link is shown, and the manner in which the specific phase noise spectra are eventually filtered is developed.
    • The Power of Desarguesian Sets

      Wu, W. W.; Communications Satellite Corporation (International Foundation for Telemetering, 1978-11)
      A Desarguesian set is a planar Euclidean geometry difference set which can be used to derive new cyclic block codes, convolutional self-orthogonal codes, and random multiple access codes. This paper discusses the usefulness of these codes and presents the step-by-step procedure for the purpose of constructing such sets. Comparisons are also made with planar projective geometry sets in which two types of existing codes were obtained.
    • Processing Satellites

      Omura, Kim; University of California, Los Angeles (International Foundation for Telemetering, 1978-11)
      With few exceptions, satellite communications systems today employ conventional nonprocessing satellites that are often referred to as "bent pipes in the sky." These satellites merely act as nonlinear (TWT) amplifiers that transmit on the downlink the same signals plus noise (frequency shifted) that it receives on the uplink. It is now clear that the "micro-processor revolution" will impact on satellite technology and result in a new generation of communication satellites with various on-board digital processing. The orbiting experimental military satellites Les-8/9 are the first-of the new generation of processing satellites. Many more such satellites are now being considered with increasingly complex digital processing on the satellites. For military applications these on-board processing capabilities are listed below in increasing order of complexity.
    • Pulse to Pulse Encoding in Optical Communications

      Prati, G.; Gagliardi, R.; University of Pisa; University of Southern California (International Foundation for Telemetering, 1978-11)
      Optical pulsing of a laser beam provides a convenient manner for transmitting digital information, and such procedures have led to well-accepted classes of pulse amplitude and pulse position modulation formats. However the excessive pulse dispersion and background light bursts that characterize several optical channels severely limit performance and achievable data rates. One procedure for combating these effects is to encode data over a multiple of pulse frames, and decode sequences of pulses rather than each pulse individually. In the paper pulse to pulse encoding and decoding of an optical beam is examined, considering both photodector gain effects and receiver thermal noise. Theoretical performance results are presented, and the relation between this type of decoding and "tree searching" is developed.
    • Quantization for Signal Detection and Representation

      Kassam, Saleem A.; University of Pennsylvania (International Foundation for Telemetering, 1978-11)
      For digital representation of analog data the minimum mean-squared-error criterion is commonly used as a criterion for the basis of optimum quantizer design. In this paper we show that in some situations measures other than the minimum mean-squared-error may be more appropriate. For the signal representation problem, it is shown that the mean-absolute-error criterion has theoretical justification, as again for some signal detection problems it is shown that the mean-squared-error criterion is not the most appropriate criterion.