• 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.
    • 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.
    • 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.
    • SEASAT-A: An Experiment in End-to-End Information System Design

      MacMedan, Mervyn L.; NASA Jet Propulsion Laboratory (International Foundation for Telemetering, 1978-11)
      The SEASAT-A ocean dynamics monitoring satellite was designed with a keen awareness of the problems of handling huge volumes of data from an Earth-orbiting applications mission. An "End-to-End" approach to the entire information system was adopted very early in the life of the Project. Some innovations introduced include the provision of a "Packet Telemetry" system which is very similar to the NEEDS program objectives, and the incorporation of an adjustable satellite clock which directly time-tags the sensor data in GMT. This paper will review the mission and information system performance, and will summarize lessons learned from the experiment in system design.
    • 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.
    • High Density 42-Track Magnetic Tape System

      Montgomery, J. H.; Martin Marietta Corporation (International Foundation for Telemetering, 1978-11)
      Design and development of a 42-track high density magnetic tape system for the NASA SEASAT program is described. Both record and playback at a nominal 120 megabits per second from a single data stream was achieved on a 1-inch mylar tape with bit error rate better than 1 x 10⁻⁶ without error correction. Solutions are presented to the requirements of data encoding, high bit rates, recovery from tape dropouts, and efficient use of tracks. This now operational system features a Channel Performance Status Panel, a Tape Bypass Mode, and a MUX/DEMUX unit capable of operating at 150 megabits per second.
    • Simulation of Two Bandwidth Efficient Modulation Efforts in Satellite Communications

      White, Brian E.; The MITRE Corporation (International Foundation for Telemetering, 1978-11)
      A bandpass limited satellite channel with uplink and downlink noise was simulated for several constant envelope modulation schemes. Minimum shift keying (MSK) significantly outperformed quadriphase shift keying (QPSK) in achieving bit error rates of 0.005 with less than 1 dB degradation for a channel bandwidth to data rate ratio B/R = 0.78, for example. Frequency division multiple access (FDMA) scenarios with unsynchronized satellite signals were also simulated. A processing satellite performed the functions of Doppler and symbol timing correction and demodulation of each uplink. Additional filtering mitigated intersymbol interference (ISI) deliberately introduced for spectral shaping by prolate spheroidal data windows. Even when the received power in each satellite signal was 10 dB above the desired signal, 16 kbps rate-1/2 coded QPSK satellite signals on odd 12.5 kHz centers could coexist with line of sight (LOS) signals on 25 kHz centers. These results are applicable to the ever growing problems deriving from increased spectral occupancy.
    • Spectral Shaping Without Subcarriers

      Welch, Lloyd R.; University of Southern California (International Foundation for Telemetering, 1978-11)
      For proper operation of the phase lock loop which tracks a carrier it is important to minimize the spectral energy at frequencies near the carrier. A traditional method is to modulate the data onto a subcarrier in such a way that there is little energy near D.C. The resulting signal then is used to modulate the carrier. The problem with such a scheme is that the total bandwidth is much larger than necessary to transmit the data. This paper proposes and analyzes a simpler scheme which increases the data bandwidth by a very small fraction, yet reduces the energy near D.C. to nearly zero.
    • A Coherent Receiver for QPSK and SQPSK Signals

      Alem, W. K.; Weber, C. L.; Axiomatix; University of Southern California (International Foundation for Telemetering, 1978-11)
      A demod-remod type of coherent tracking loop for conventional QPSK and staggered QPSK (SQPSK) is presented. The phase detector characteristic (S-curve) is determined. The effects of power unbalance and arm gain unbalance on the S-curve are presented. The steady state rms phase error is shown as a function of the signal-to-noise ratio at the output of the arm filters.
    • INTELSAT V Spacecraft Antenna Subsystem

      Jakstys, V. J.; Ward, H. T.; Ford Aerospace and Communications Corporation (International Foundation for Telemetering, 1978-11)
      Design and development has been completed on the Antenna Subsystem for the INTELSAT V Communications Satellite. The Communications antennas include two C-Band (transmit and receive) Hemi/Zone coverage antennas, two C-Band (transmit and receive) Earth Coverage antennas, two 11/14 GHz Spot Beam antennas and an 11 GHz Beacon antenna. The C-Band Telemetry and Command antennas consist of two directional beam telemetry (transmit) antennas, a dual-port toroidal beam telemetry antenna and two cardioid beam command (receive) antennas. The designs have been verified by measurements, and the test results indicate that all major performance requirements will be achieved.
    • The Wide-Band Signal Processor

      Stiffler, J. J.; Raytheon Company (International Foundation for Telemetering, 1978-11)
      The Wide-Band Signal Processor (WBSP) is a spaceborne communications processor designed to operate as a peripheral to the Fault-Tolerant Spaceborne Computer (FTSC) currently being developed for the U. S. Air Force. Its function is to demodulate and decode received FDM and TDM signals and to re-encode the recovered information and use it to modulate signals for retransmission. The major difference between the WBSP and other processors designed to perform similar functions is in the fact that the WBSP, like the FTSC itself, is designed to survive its own hardware malfunctions.
    • 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.
    • International Telemetering Conference Proceedings, Volume 14 (1978)

      International Foundation for Telemetering, 1978-11
    • 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.
    • Step-By-Step Decoding of Alternant Codes

      Omidyar, C. G.; Helgert, H. J.; The George Washington University (International Foundation for Telemetering, 1978-11)
      In this paper we present a decoding scheme for Alternant codes. The syndromes are calculated from the received vector and the parity check matrix H. Let t be the error correcting capability of the decoder. Then we determine a Key Equation by adding t columns of the parity check matrix H. We raise this equation t-1 times to the power of n, where n is the number of columns of H. Next we consider a matrix At whose elements are the set of coefficients from the Key Equations which we obtained. We make a decision based on the determinant of the matrix A(t). If the matrix A(t) is singular, then we test the matrix A(t-1) for singularity and continue up to A(t-t+1) which in fact the decoder can correct one error. if any one of the matrices A(t) through A(t-t+1) is nonsingular we change the first digit of the received vector, then recompute the syndromes and recheck Δt'. If Δt' is zero the change is retained. If not, the digit is changed again. The Algorithm then proceeds to the next digit. This Algorithm for decoding Alternant codes has significant improvements over previous schemes since the step-by-step decoding can be carried out at selected areas of the received word.
    • 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.
    • The LES-8/9 Telemetry System: Pt II, Ground Terminal Design and Performance

      Helfrich, J. H.; Gjelsvik, A. M.; Rader, C. M.; Rogers, D. C.; Small, C. E.; Massachusetts Institute of Technology (International Foundation for Telemetering, 1978-11)
      The LES-8/9 telemetry ground terminal is a distributed system providing simultaneous reception of digitally encoded telemetry from both LES-8 and LES-9 satellites via S-band, K-band, and UHF downlinks at ground commendable rates of 100-bps and 10-Kbps. Antenna control and demodulation as well as frame synchronization and error detection are provided at a centralized facility, and resultant baseband telemetry is distributed in processed digital format over serial-data lines through a coaxial-cable distribution network. Comprehensive, realtime telemetry processing is provided by separately located minicomputers which provide alphanumeric data displays to a distributed network of standard TV-type video monitors. Telemetry is recorded directly in IBM compatible form under minicomputer control and selection, with post-processing performed at the IBM-370 Lincoln Computation Center. Additional real-time processing is also provided by dedicated panels portraying subsystem operations. Extensive operational software has been developed for evolving needs from initial satellite integration and test through post-launch operation and monitoring. These programs as well as the related hardware equipment and organization are described and traced through the course of the LES-8/9 project.
    • The LES-8/9 Telemetry System: Pt I, Flight System Design and Performance

      Sarles, F. W.; Helfrich, J. H.; McKenzie, P. F.; Roberge, J. K.; Massachusetts Institute of Technology (International Foundation for Telemetering, 1978-11)
      LES-8 and LES-9 are two experimental communication satellites designed and built for the Air Force by the M.I.T. Lincoln Laboratory. The on-board telemetry systems were designed not only to monitor the spacecraft on orbit but also to provide significant test support capability during subsystem development and spacecraft integration and test. Each system is configured in a distributed form, with remote Telemetry Input Converters (TICs) located in various subsystems communicating with a central Telemetry Output and Control (TOC). Salient features include 1) modular design of TICs permitting tailoring to specific subsystem requirements, 2) accurate analog measurement capability (.025% of full scale) over 140EC ambient temperature (-60°C to +80°C), 3) cross-checking of analog-to-digital converters via a high stability (50 microvolts) stepped calibration source, 4) flexible word allocation permitting late freezing of formats, 5) digital organization with individual parity check on each word, 6) sub multiplexing capability, 7) dual speed operation at 100 bps and 10-Kbps, and 8) downlink capability via a variety of rf links. Descriptions of overall operation and performance along with design considerations in critical areas are covered in detail.
    • TIPS Telemetry Compiler

      Billerbeck, G.; Idsardi, R.; System Development Corporation (International Foundation for Telemetering, 1978-11)
      The TIPS Telemetry Compiler is a keyworded-free format language processor used to generate run-time tables for controlling the real-time software and front-end hardware of the Telemetry Integrated Processing System (TIPS) at Vandenberg Air Force Base. The use of a compiler shortens response time to new requirements and improves analyst productivity. The Telemetry Source Language (TSL) is the interface between the telemetry analyst and the compiler. For example, TSL statements are used to specify parameters for the telemetry stream, compression algorithms, data acquisition, display, and history recording. Considerable flexibility has been built into the internal structure of the compiler by the use of an Input Control Definition Language (ICDL) to define the construction of the TSL. The flexibility provided by the use of an ICDL to map the source language into the compiler data base is essential for adapting the compiler to requirements beyond the scope of the original construction. The compiler data base is sufficiently large and complex to require the implementation of data base management and memory management techniques. The nature of these facilities is important for a modular architecture and for reasonable computational efficiency. These key features of the internal structure of the Telemetry Compiler are transparent to the Compiler user. The output of the compiler is a Run-Time File for use by the Real-Time Software in loading the programmable front-end hardware and in software process control. The TIPS Telemetry Compiler is written in structured FORTRAN on a CDC CYBER 173. The real-time software executes on a network of SEL 32/55 processors. At the time of publication, the framework of the compiler was completed as well as major portions of the run-time file generation phase, and the compiler had been used to build run-time files for major development milestones.
    • 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.