RSS 1.0International Telemetering Conference Proceedings, Volume 23 (1987)
ABOUT THE COLLECTION
The International Telemetering Conference/USA (ITC/USA) is dedicated to the promotion and stimulation of technical growth in telemetering and its allied arts and sciences. It is the premier annual forum and technical exhibition providing telemetry specific short courses, technical papers from professionals and students, and exhibits of the industry’s leading companies. ITC/USA is sponsored by the International Foundation for Telemetering (IFT), a non-profit corporation dedicated to serving the technical and professional interests of the telemetering community.
This collection contains the proceedings of the twenty-third International Telemetering Conference, October 26-29, 1987. The conference, sponsored by the International Foundation for Telemetering, was held at the Town and Country Hotel in San Diego, California.
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International Telemetering Conference Proceedings, Volume 23 (1987)International Foundation for Telemetering, 1987-10
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An Asynchronous Digital Interface for SLAT TelemetryThis paper describes telemetry used in the Supersonic Low Altitude Target (SLAT) built for the U.S. Navy by Martin Marietta. Feeding digital inputs directly to a pulse code modulation (PCM) encoder, bypassing the analog-to-digital (A/D) converter, and injecting into the output PCM wavetrain is well known. Various techniques for accomplishing this have been reported; however, they all have time correlation and synchronization problems. The system to be described involves asynchronous data transfer from the digital computer to the PCM encoder. The system uses a dual-port random-access memory (RAM) to effectively decouple the computer output, which is running synchronously on its 6 MHz clock, from the PCM wavetrain, which is running at 128 kilobits per second. Data from the computer is being "written into" the RAM simultaneously while data is being "read out." Contention arbitration prevents loss of data when read and write ports of the same address are activated. A "forbidden code" provides a special code when the computer is not connected or is producing all zeros.
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ReConTTA: A State-Of-The-Art Telemetry Tracking SystemThe purpose of this paper is to present and discuss key features of a Remotely Controllable Telemetry Tracking Antenna (ReConTTA) system which, truly, represents the current state-of-the-art. The ReConTTA system is planned to support flight testing of all current and future generation aircraft at the Air Force Flight Test Center (AFFTC), Edwards Air Force Base, California. System features to be discussed include: (1) The Antenna Group including Radial Scanning (RADSCAN). (2) The Local Control Group and its interface with the down converting, r-f switching, receiving, diversity combining, and microwave data-link equipment. (3) The Remote Control Group and its interface with microwave and ground station processing equipment. Several examples will be presented, illustrating the capabilities of the ReConTTA system, including the following: (1) Remote control operations utilizing computer control. (2) Broadband frequency coverage from 1435-2400 Mhz. (3) Low tracking angle performance.
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The Generic Data Capture FacilityThe growing complexity of space science missions is causing a dramatic increase in the data rates and volumes from spaced-based experiments, and the ground operations functions associated with handling data from these missions are growing in complexity consistent with this increase. A key requirement on the systems that provide data handling support is to control operations costs carefully while providing high-quality data capture functions. One approach to meeting this particular objective that has been taken at the Goddard Space Flight Center has been to initiate the development of a Generic Data Capture Facility (GDCF) that can provide data capture support for a variety of different types of spacecraft. The GDCF is emerging through a blend of new system development and evolution of existing systems, and when complete, it will have the capability to support the two major data formatting schemes (packet and Time-Division Multiplexed (TDM)). The specific implementations are designed to support the Gamma Ray Observatory and the Upper Atmosphere Research Satellite, but the GDCF will provide the baseline system to support various new missions as they emerge.
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A Data Handling and Linking System for all of NASA's Near Earth Space MissionsA modularized data handling and linking system is evolving that will meet all of NASA's low earth orbiting space needs. The system is comprised of three major subsystems: (1) Data management (three networks; 300 Mbps to 20 Mbps, 20 Mbps to 3 Mbps, and 3 Mbps to 125 bps); (2) RF (antennas and microwave components); and (3) antenna control. Representative system components, approximately 70% of a total system, have been tested operating through the NASA Tracking and Data Relay Satellite System in May 1987. The modularized concept and data bandwidth transitions of the data management subsystem utilizes recently developed flight components along with developmental models that results in a system that is cost effective with a high level of performance and reliability. The system concept with performance data of key components will be presented.
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An Implementation of Concatenated Coding Scheme on Indian SpacecraftA Concatenated Coding Scheme to provide an extremely 'clean' channel is suggested for onboard spacecraft telemetry system by the Consultative Committee for Space Data Systems (CCSDS). The outer code is a Reed Solomon block code and the inner, a Viterbi or Convolutional Code. The Gaussian channel are corrected by the inner code. However, the Viterbi decoder may introduce some burst errors. These are then corrected by the Reed Solomon decoder. The inner Viterbi code (K=7, rate 1/2) was developed and implemented for the first time in RSD2 (Rohini series) satellite. The outer code has not yet been implemented onboard spacecraft since the decoder has not been fully developed. However, the onboard encoding system (255,223) has been developed and tested. This paper describes the development and implementation of Viterbi encoder in RSD2 satellite along with its inorbit performance.
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Effects of Co-Channel Interference with Frequency Offset on PSK SignalsThe sharing of C-band between microwave terrestrial and satellite communication systems invariably introduces interference from one system into the other. Such co-channel interference becomes even more important in satellite receive stations with smaller antennas and must be minimized to achieve system performance objectives. In this paper, co-channel interference due to two TD2 (FDM/FM) carriers into a satellite receive system, receiving binary phase-shift keyed (BPSK) signal, is considered. It is shown that the frequency offset of the TD2 carriers from the BPSK carrier can be used to minimize co-channel interference effects. Equations are given which compute the bit error rate (BER) of BPSK signals in the presence of an interfering unmodulated carrier. They are followed by some results due to TD2 carrier interference.
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Phase Tracking Error in a Fading ChannelThe phase tracking error of the reception of a QPSK signal transmitted in a severe fading environment is derived. The phase estimate derived from the phase lock loop (PLL) will be used by a binary phase shift keying (BPSK) receiver for the recovery of the data. The resultant probability of bit error is analyzed, and is shoen to be significantly improved when the phase of the transmitted signal is tracked by a PLL separately and utilized in the coherent detection.
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Interagency ArrayingVoyager ground aperture requirements for Neptune encounter in August 1989 exceed the expected capabilities of the Jet Propulsion Laboratory's Deep Space Network (DSN) 70- and 34-meter antennas. Agreements have been consummated with the National Science Foundation to array the National Radio Astronomy Observatory's Very Large Array in New Mexico and with the Commonwealth Scientific and Industrial Research Organization's Parkes Radio Telescope in Australia with the DSN. This technique, which was demonstrated during Voyager's Uranus encounter, will provide a greater return of imaging and non-imaging science data. The arrays consist of the normal facility receiving equipment at each location, augmented by special receiving, combining, recording, and monitor and control equipment. This equipment has been designed, is being implemented, and will be operated during the Neptune encounter to effectively double the available antenna aperture over the western United States and Australia.
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Voyager Image Data Compression and Block EncodingTelemetry enhancement techniques implemented through flight software modifications and utilization of special flight hardware enable the Voyager 2 spacecraft to reduce telemetry transmission rates used at Saturn by over 50% for the extended mission to Uranus and Neptune with negligible loss in information return. Techniques employed include: * Parallel operation of the redundant Flight Data Subsystem (FDS) processors * Image Data Compressor (IDC) using noiseless (fully reconstructable) coding techniques * Reed-Solomon (RS) encoding of downlink telemetry.
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Voyager-Neptune Telemetry: The DSN 70 Meter Antenna UpgradeThe Deep Space Network is responsible for the acquisition of in-situ science and engineering measurements and navigation data from spacecraft whose missions are to explore the Solar System. It must respond to new opportunities in the mission set supported so as to maintain or enhance mission science value. The large capital investment in such a Network mandates an evolutionary design approach wherein upgrades can be effected at low cost, and if appropriate, on existing capability. The 64-Meter antenna design, completed in 1963, is an example of this approach, in that it has permitted a relatively low-cost upgrade which increases performance significantly. The technology assessment was completed in 1975, and the option was exercised in 1986, when needed. Several key characteristics of the DSN design approach, the costs to upgrade performance over the past several decades, and some fundamental constraints on performance are discussed. Finally, the specific 70-Meter upgrade task and resulting overall benefits to Voyager-Neptune and the mission set are summarized.
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A 4 Mbps Digitizer with 100 kHz Signal BandwidthThis paper presents a non-standard digitization scheme which samples the data asymmetrically in order to maximize data bandwidth. Two frame sychronization words are utilized in a separated manner to permit their replacement with the average value of adjacent data words during the decommutation process.
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New Concepts in PCM EncodingThe Pulse Coded Modulation (PCM) Encoder Systems used in telemetry have gained enormous flexibility for various applications because the input data channels and frame sync codes are programmable via the EEPROMs or UVEPROMs. The firmware in the current PCM Encoder Systems can be readily tailored for a specific application to monitor numerous types of analog channels, as well as digital channels. However, the current PCM Encoder Systems require several types of strap options which dictate not only a limited choice of gains and offsets, but also a fixed choice of the premodulation filter characteristics. The brain of the 1000 PCM Encoder is the Digital Signal Processor (DSP) which eliminates the fixed premodulation filter characteristics via digital filter functions, and also eliminates strap options via general purpose microprocessor functions.
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A Technical Comparison of Frequency and Phase Modulation Relative to PCM Data Transmission SystemsDirect experience in the design and developement of airborne telemetry systems utilizing both principles of modulation. System level analysis of receiver phase coherency, bit sync error codes, data band width, transmission efficiency and overall system complexity. High reliability, miniaturized packaging and HI-G survivability will be stressed as well as illustrated.
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Binary Decision Machines: Alternative Logic for Telemetry ControlA Binary Decision Machine (BDM) is described as a means of achieving logical control of data acquisition equipment and telemetry systems. The basic architecture of a BDM is initially presented followed by a description of its implementation as a Very Large Scale Integration (VLSI) device. Performance characteristics, programming, and ease of use as a controller are then presented via actual applications. The results of these endeavors led to a means of digitizing and extracting doppler data in a missile telemetry system.
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The Real-Time Telemetry Processing System IIIThe Navy's Real-time Telemetry Processing System (RTPS III) is a third generation system. Designed and built by Computer Sciences Corporation (CSC), RTPS III will support the demands of the Navy flight test community well into the 1990's. The RTPS III is custom-crafted using CSC's system development methodology which blends the best features of the current Navy RTPS system and previously proven CSC systems. A major objective of CSC's RTPS III design is the continuation of existing Navy user interfaces. The transition from the existing system to the integrated RTPS III has also been facilitated by the incorporation of common interfaces to Navy applications software, thus ensuring "new system" acceptance. RTPS III is designed to include a powerful front-end capable of Engineering Unit conversions at more than 200,000 samples per second (sps) per telemetry stream with expansion to 500,000 sps. It will include networking concepts which allow the simple addition of additional subsystems should expansion be required. RTPS III also supports both secure and integrated modes of operation for classified and unclassified processing. The CSC design, a custom combination of proven and new development, results in a Navy system which meets tomorrow's flight test requirements today. Other benefits to NATC are a modular, cost-effective solution with lower life-cycle costs, and a broader range of possibilities for evolving and reconfiguring the system to service new applications and users.
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Data Handling System for IRSThe three axis stabilized Indian Remote Sensing Satellite will image the earth from a 904 Km polar - sun synchronous orbit. The payload is a set of CCD cameras which collect data in four bands visible and near infra-red region. This payload data from two cameras, each at 10.4 megabits per sec is transmitted in a balanced QPSK in X Band. The payload data before transmission is formatted by adopting Major and Minor frame synchronizing codes. The formatted two streams of data are differentially encoded to take care of 4-phase ambiguity due to QPSK transmission. This paper describes the design and development aspects related to such a Data Handling System. It also highlights the environmental qualification tests that were carried out to meet the requirement of three years operational life of the satellite.
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Trends in Space Shuttle Telemetry ApplicationsDuring 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.
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Space Shuttle Data Formatter DSI Model 7303 SystemThis abstract describes the hardware and software necessary for reserialization of asynchronous imbedded image data. The purpose of the DSI Model 7303 System is to reformat space shuttle imbedded (Payload Data Interleaver) PDI data. the system consists of two decoms, a DSI model 7303A and a DSI Model 7303B. The input to the 7303A box is 0I or NSP data (NRZ-L & CLOCK). The 7303A Frame syncs to the 0I or NSP data. The 7303A is front panel programmed to strip out only the imbedded PDI data and pass this data to the 7303B Decom. The 7303B Frame syncs to the PDI frame sync pattern. A second strip zone defines which words in the PDI frame get passed to the FIFO. A 24K byte ring FIFO Buffer is used to buffer data before reserialization for output. The serial output rate is a function of how many programmed PDI words per second are stripped out and the FIFO management status. The output bit rate is from a microprocessor controlled NCO. This system Makes possible real time video of Shuttle PDI data.
