• Telemetry Handling on the Space Station Data Management System

      Whitelaw, Virigina A.; NASA - Johnson Space Center (International Foundation for Telemetering, 1987-10)
      Traditional space telemetry has generally been handled as asynchronous data stream fed into a time division multiplexed channel on a point-to-point radio frequency (RF) link between space and ground. The data handling concepts emerging for the Space Station challenge each of these precepts. According to current concepts, telemetry data on the Space Station will be packetized. It will be transported asynchronously through onboard networks. The space-to-ground link will not be time division multiplexed, but rather will have flexibly managed virtual channels, and finally, the routing of telemetry data must potentially traverse multiple ground distribution networks. Appropriately, the communication standards for handling telemetry are changing to support the highly networked Space Station environment. While a companion paper (1. W. Marker, "Telemetry Formats for the Space Station RF Links") examines the emerging telemetry concepts and formats for the RF link, this paper focuses on the impact of telemetry handling on the design of the onboard networks that are part of the Data Management System (DMS). The DMS will provide the connectivity between most telemetry sources and the onboard node for transmission to the ground. By far the bulk of data transported by DMS will be telemetry, however, not all telemetry will place the same demands on the communication system and DMS must also satisfy a rich array of services in support of distributed Space Station operations. These services include file transfer, data base access, application messaging and several others. The DMS communications architecture, which will follow the International Standards Organization (ISO) Reference Model, must support both the high throughput needed for telemetry transport, as well as the rich services needed for distributed computer systems. This paper discusses an architectural approach to satisfying the dual set of requirements and discusses several of the functionality vs. performance trade-offs that must be made in developing an optimized mechanism for handling telemetry data in the DMS.
    • High Data Rate Reed-Solomon Encoding and Decoding Using VLSI Technology

      Miller, Warner; Moakis, James; Goddard Space Flight Center (International Foundation for Telemetering, 1987-10)
      Presented as an implementation of a Reed-Solomon encoder and decoder, which is 16-symbol error correcting, each symbol is 8 bits. This Reed-Solomon (RS) code is an efficient error correcting code that the National Aeronautics and Space Administration (NASA) will use in future space communications missions. A Very Large Scale Integration (VLSI) implementation of the encoder and decoder accepts data rates up to 80 Mbps. A total of seven chips are needed for the decoder (four of the seven decoding chips are customized using 3Fm Complementary Metal Oxide Semiconduction (CMOS) technology) and one chip is required for the encoder. The decoder operates with the symbol clock being the system clock for the chip set. Approximately 1.65 billion Galois Field (GF) operations per second are achieved with the decoder chip set and 640 MOPS are achieved with the encoder chip.
    • Trends in Space Shuttle Telemetry Applications

      Muratore, John F.; Lyndon B. Johnson Space Center (International Foundation for Telemetering, 1987-10)
      During early manned spacecraft operations, the primary role of ground telemetry systems was data display to flight controllers. As manned spaceflights have increased in complexity, greater demands have been placed on flight controllers to simultaneously monitor systems and replan systems operations. This has led to interest in automated telemetry monitoring systems to decrease the workload on flight controllers. The Mission Operations Directorate at the Lyndon B. Johnson Space Center has developed a five layer model to integrate various monitoring and analysis technologies such as digital filtering, fault detection algorithms, and expert systems. The paper describes the five layer model and explains how it has been used to guide prototyping efforts at Mission Control. Results from some initial expert systems are presented. The paper also describes the integrated prototype currently under development which implements a real time expert system to assist flight controllers in the Mission Control Center in monitoring Space Shuttle communications systems.
    • Recent Trends in PSK Demodulation

      Roberts, R. H.; Tremain, George F.; Decom Systems, Inc. (International Foundation for Telemetering, 1987-10)
      Increased usage of PSK signals in TT&C formats has generated unique challenges for ground support equipment developers. DSI has met this challenge with the introduction of its model 7133 BPSK / QPSK modem. Enhanced on the Aerojet / USAF GS-14 program, the 7133 is the latest addition to the company's modem product line. The 7133 uses a dual mode cross arm Costas loop to demodulate BPSK or QPSK data. With an implementation loss averaging 0.8 dB, the 7133 demodulates asynchronous 2.56 MBps QPSK data. It also processes BPSK data at rates up to 2.56 MBps, with a loss of less than 0.5 dB. We present the 7133 demod design and test results. Current work at DSI extends the basic 7133 design to handle unbalanced QPSK formats. DSI's new model 7750 receiver-demodulator processes quadrature input signals either in pairs or independently. The 7750 uses phase locked loops to demodulate PSK, FM, PM or AM. We present the 7750 extended Costas loop design and preliminary test results. Finally, we look at applying recent DSP and NCO IC's to multi-mode TT&C demodulation.
    • Spectrum Utilization for the International Space Station Communications and Tracking Systems

      Novosad, Sidney W.; Johnson Space Center (International Foundation for Telemetering, 1987-10)
      Over its lifetime, the international Space Station Program will use a variety of communications and tracking systems which could span the frequency spectrum from VHF to optical wavelengths. Primary communications traffic will initially occur in the S-band and Ku-band regions. Tracking will initially consist mostly of L-band satellite links. As the demand for more C&T services increases in the growth phase, use of millimeter and optical wavelengths will be required. Although many issues remain to be resolved, the most significant interference concern at present is that of Ku-band space/space links between co-orbiting Space Station elements.
    • A Distributed Systems Approach to Real-Time Data Acquisition and Monitoring

      Fidell, Sanford; Fortmann, Thomas; Moss, Peter; BBN Laboratories, Inc. (International Foundation for Telemetering, 1987-10)