Now showing items 21-40 of 59

    • A Central Controller/Display System with Real Time Processing for Remote Data Acquisition Units

      Prichard, Guy D.; Teledyne Controls Company (International Foundation for Telemetering, 1974-10)
      A flexible Data Management and Display Unit (DMDU) has been developed as part of the On-Board Data System developed for the 40' x 80' Wind Tunnel at Ames Research Center. The DMDU can be operated as a slave to a Systems Engineering Laboratories Model SEL-840MP computer or as a standalone system receiving instructions from an operator via data terminal/keyboard inputs. It is capable of controlling the acquisition data from four data acquisition units at software selectable word rates of 250 to 125,000 words per second in increments of 50 words per second. The number of remote acquisition units can be expanded to twenty-nine units providing data point capacity in excess of 10,000 channels. Acquired data can be distributed in real time to the host computer (SEL-840MP), a bar graph CRT display (up to 128 data points), a strip chart recorder (up to 3Z data points), to one or both of two analog magnetic tape recorders (BI0/ -L or DM-M format) or to a PDP-11/05 minicomputer for data processing in real time. The DMDU can be utilized as a "quick-look" playback facility for the playback and display of data previously recorded on magnetic tapes in any of the standard IRIG PCM formats. It receives initialization information consisting of the remote acquisition units and data point address, amplifier gain, each data points required sampling rate and the data output destination entered locally via punched paper tape or from the SEL-840MP computer. Resident software generates a "master sampling format" with sub-commutation and super-commutation as required. Embedded within the master cycle are the minor cycle sampling formats for the individual recorder outputs, complete with software controllable fram ' e synchronization patterns. Conversion from the data acquisition mode to the data playback or data reduction mode can be performed dynamically under interrupt control.
    • An Integrated PCM Data System for Full Scale Aeronautics Testing

      Reynolds, Don R.; Ames Research Center (International Foundation for Telemetering, 1974-10)
      An integrated PCM data system is being developed at Ames Research Center to gather test data on advanced STOL propulsive lift, VTOL, rotary wing, and V/STOL control systems concepts as they pass through wind-tunnel, test-stand, flight-simulator and flight-test phases. Identical airborne signal conditioning and PCM encoding is used on test aircraft and wind tunnel models. An 80,000 word/second PCM installation will be the first "all PCM" instrumented rotary wing development project. The system uses both dedicated and time-shared computers for fast data analysis with maximum use of resources. This system development shows one way to bring separate data user groups together over a common data base, while sharing computing resources for minimum cost.
    • Firmware Controlled, High Speed, Random Data Acquisition Unit

      Trover, William F.; Teledyne Controls Co. (International Foundation for Telemetering, 1974-10)
      A firmware controlled, integrated data acquisition unit for computer controlled or standalone operation reduces the users Data Acquisition system programming task to preparation of a parameter list in IBM card deck format. Data cycle format generation is accomplished on a host computer which produces program tapes for the Data Acquisition system's field erasable PROM format memory. The completely random data system can be programmed for a wide spectrum of data cycle sizes. Cycle rate can be remotely controlled in flight permitting the operator to select any of 256 word rates from 244 WPS to 125,000 WPS. Analog and digital signal conditioning can be included in the unit which also provides excitation power for all conventional sensors. Sensor capacity is from 44 to 352 channels depending on the type of signal conditioning required for a specific application. Up to eleven of over 20 different types of signal conditioner/ multiplexer I/O modules, plus the overhead modules and the system power supplies, may be accommodated at one time in a package of less than 450 cu in. (4" x 8" x 14"). All I/O cards and modules regardless of type are interchangeable at any of the eleven I/O locations in the unit housing. A miniature data display module which can be mounted in any standard cockpit control console permits the pilot or test engineer to have real time access during flight to any data point in the system. Two or more data systems may be used at remote locations in the same aircraft in synchronized operation to accommodate higher data throughput rates without increasing recorder bandwidth requirements by recording separate serial data streams on parallel tracks of a single multi-track recorder. Ground support equipment permits sensor installation, calibration and system checkout without the need for aircraft ground power or finalization of a sampling format for a test flight. Interchanging the Standalone Timing Module with a Digital Processor Module permits the Data Acquisition Unit to become a remotely controlled bidirectional data processor of a larger system performing both data acquisition and control loop functions.
    • Odd-Bit Symmetric QASK

      Smith, Joel G. (International Foundation for Telemetering, 1974-10)
      Multiple-amplitude and phase-shift- keyed (MAPSK) signal set selection is influenced by factors such as average and/or peak signal-to-noise ratio for a given error probability, dynamic range of signal amplitudes, simplicity of generation and detection, and number of bit errors per adjacent symbol error. This paper compares two possible quadrature-amplitude-shift-keyed (QASK) signal sets for the case where the number of bits per symbol is odd (for the even-bit case, the square array is the only viable QASK choice). The symmetric QASK version outperforms the rectangular QASK set at a very modest implementation penalty. This permits symmetric QASK to be considered in future odd-bit system studies.
    • Performance of a Tracking Status Detector for a Digital Delay Lock Loop

      Holmes, J. K.; Chen, C. C. (International Foundation for Telemetering, 1974-10)
      A tracking status detector, operating on the principal of detecting the instantaneous phase error is considered in conjunction with a noncoherent τ-dither loop. This detector offers a significant improvement in performance as compared to the conventional loop lock detector. The out-of-lock detection when the loop is not in lock is modeled as a Markov process and the detection probability is the probability that the phase error accumulator (or a digital counter) exceeds a preset threshold in a fixed T seconds. The other performance parameter, the probability of false alarm, is also obtained using a Markov model. The results indicate that at a signal-to-noise ratio of 6 dB, the probability of out-of-lock detection of 0.9999 is attainable. The probability of one or more false alarms in one year was less than 10⁻⁵. A brief discussion on the frequency drift estimator based on the same principal is also included.
    • Analysis and Test Results of a Hybrid PCM/FM-subcarrier Baseband Multiplex on an FM Carrier

      Nichols, M. H.; The Aerospace Corporation (International Foundation for Telemetering, 1974-10)
      Engineering formulae have been developed for estimating the performance of a telemetry system utilizing an NRZ PCM multiplex plus an FM/FM multiplex frequency modulating a carrier. These formulae have been checked against a laboratory simulation and the agreement is within 1 dB for the PCM and 1.8 dB for the FM/FM. About 1 dB of the 1.8 dB is tentatively accounted for on the basis of lack of symmetry of the carrier predetection (IF) filter used.
    • Space Shuttle Antenna Subsystem Design

      Ellis, H.; Cubley, H. D.; Symonds, Richard J.; Rockwell International; NASA/Lyndon B. Johnson Space Center (International Foundation for Telemetering, 1974-10)
      The unique nature of the Shuttle orbiter is that all of its systems must meet the design requirements of a spacecraft as well as the basic aircraft requirements for atmospheric flight. The Shuttle antenna system design, therefore, faces many unique problems. Some of the most significant of these problems include the interface with the Shuttle thermal protection system, the wide range of thermal extremes and rates to be encountered, the long life requirement, and the need for lightning protection. In addition, the radiation coverage requirements of some of the Orbiter antennas are complicated by the multiple requirement for operation during launch, from earth orbit to both ground station and relay satellites, and to the landing area during atmospheric flight. The unique engineering problems that result from these requirements will be described along with techniques that are planned for their solution.
    • Remote Monitoring of Ozone in the Troposphere Using Earth Reflected Differential Absorption

      Guagliardo, John L.; Bundy, Donald H. (International Foundation for Telemetering, 1974-10)
      A method of remotely monitoring the tropospheric concentration of ozone is proposed. The method uses two lasers, each emitting a different wavelength. It is shown that even though only two laser wavelengths are used, the method is both specific and accurate for concentrations which are encountered in most urban areas.
    • Ambient and Industrial In-Situ Emissions Monitoring

      Lord, H. C.; Environmental Data Corporation (International Foundation for Telemetering, 1974-10)
      Most of the papers presented here deal with remote measurements of pollutants either from an emission source, or in the ambient air. This paper deals with an alternative route: The utilization of rugged, reliable instrumentation located in-situ. This instrumentation, based upon absorption spectroscopy, gives a specific and instantaneous analysis of multiple parameters (typically up to five) without sample handling or conditioning.
    • The Laser Absorption Spectrometer: A New Remote Sensing Instrument for Atmospheric Pollution Monitoring

      Shumate, M. S.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1974-10)
      An instrument capable of remotely monitoring trace atmospheric constituents is described. The instrument, called a Laser Absorption Spectrometer, can be operated from an aircraft or spacecraft to measure the concentration of selected gases in three dimensions. This device will be particularly useful for rapid determination of pollutant levels in urban areas.
    • Method and Apparatus for Collecting Impact Test Data

      Mercer, Thomas C., Jr.; GM Proving Grounds (International Foundation for Telemetering, 1974-10)
      A flexible, powerful and interactive data collection system is described based upon state of the art instrumentation and computer aided digitization and processing. The result is a highly accurate and repeatable system capable of yielding reduced engineering plots within hours after an impact test has been conducted.
    • A Computer-Controlled, On-Board Data Acquisition System for Wind-Tunnel Testing

      Finger, Herbert J.; Cambra, Joseph M.; NASA Ames Research Center (International Foundation for Telemetering, 1974-10)
      A computer-controlled data acquisition system has been developed for the 40x80-Foot Wind Tunnel at Ames Research Center. The system, consisting of several small "on-board" units installed in the model and a data-managing, data-displaying ground station, is capable of sampling up to 256 channels of raw data at a total sample rate of 128,000 samples/sec. Complete signal conditioning is contained within the on-board units. The sampling sequence and channel gain selection is completely random and under total control of the ground station. Outputs include a bar-graph displays digital-to-analog converters, and digital interface to the tunnel's central computer, an SEL 840MP. The system can be run stand-alone or under the control of the SEL 840MP.
    • Frame Sync Acquisition for Biorthogonally Coded Data

      Levitt, Barry K. (International Foundation for Telemetering, 1974-10)
      The optimum procedure for locating a sync word periodically inserted in uncoded binary data received over a binary symmetric channel is based on the Hamming or bit distance metric. This paper addresses the corresponding frame sync problem for biorthogonally coded data transmitted over the additive white Gaussian noise channel. For conceptual convenience, the k-bit words from the decoder output are treated as "super symbols" from an alphabet of dimension 2ᵏ. It is argued that the optimum sync word search over the decoded data stream is based on a super symbol distance rule matched to the properties of the biorthogonally coded transmissions over the noisy channel. An optimum frame sync acquisition algorithm based on this distance rule is formulated, and its performance is investigated. As an example, the performance of this optimum frame sync algorithm is contrasted analytically with that of a Hamming distance algorithm operating on decoded (32, 6) biorthogonal data, a case of interest to some recent unmanned American space missions.
    • A Markov Model for NASA's Ground Communications Facility

      Adeyemi, Oduoye (International Foundation for Telemetering, 1974-10)
      For those burst noise channels that can be mode l led by finite state Markov chains (FSMC) this paper presents a 'natural' way of constructing such models and in particular gives a five-state Markov chain as a model of errors occurring on the NASA's Ground Communications Facility (GCF). A Maximum Likelihood procedure applicable to any FSMC is developed for estimating all the model parameters starting from the data of error runs. Then we give a few of the statistics important for estimating the performance of error control strategies on the channel.
    • A Simple Preprocessor for Narrowband Omega Retransmission

      Raab, Frederick H. (International Foundation for Telemetering, 1974-10)
      Global distress location and search and rescue operation may utilize Omega VLF navigation signals for position determination. The rescue radio would retransmit the Omega signals to a satellite for relay to a search and rescue center, where the position of the retransmitter would be determined. Since only the phases of the Omega signal are required, preprocessing prior to retransmission can have several advantages, including reduced bandwidth, transmission, transmitter power, antenna size, and error rate. Both phase measurement and averaging can be accomplished by a simple counting phase detector. The characteristics of an Omega preprocessor using a set of counting detectors are described.
    • SAMTEC Integrated Telemetry System Analysis

      Kern, L.; Smith, B.; Miller, M.; Straehley, T.; Vandenberg Air Force Base; Logicon, Inc. (International Foundation for Telemetering, 1974-10)
      The goals of TCAS were to recommend a Telemetry Integrated Processing System (TIPS) that will improve SAMTEC mission support, increase flexibility and modularity of the system, and provide a system that is more easily operated by the range operations personnel with an associated reduction in overall operating cost. SAMTEC has completed the conceptual phase of the classical system life cycle. The validation phase is now well underway and the development phase is expected to start early in the calendar year 1975. The Integrated Telemetry System was derived utilizing the fundamentals of good engineering practices, common sense, and very extensive analysis. The resultant system should satisfy the goals of improved support, flexibility and modularity, and should provide at least a 20 to 40 percent reduction in the current telemetry processing expenditures.
    • A Flexible Preprocessor for ERTS MSS Data

      Waltz, Edward L.; Bendix Aerospace Systems Division (International Foundation for Telemetering, 1974-10)
      The requirements to preprocess Earth Resources Technology Satellite (ERTS) multispectral scanner (MSS) data from its 24 channel tape format at real time rates can be met most efficiently by a parallel processor with a flexible interface for compatibility with a wide range of digital computers. The ability of the preprocessor and tape unit to playback data at programmable rates (real-time and half and quarter real-time) provides the additional ability to adjust preprocessing rate to optimize system throughput for several image processing computer system configurations, and processing modes. The MSS Data Interface described in this paper has been developed to meet these requirements for ERTS processing facilities of those nations which record ERTS data in the NASA-compatible format on 28 channel tape units. The first MDI which has been delivered to the Brazilian government is compatible with the Digital Equipment Corporation PDP-11 computer and can be operated in either a single or dual processor system configuration.
    • Use of Pseudo-Random PCM Tape Signatures for Telemetry Ground Station Validation

      Schoeck, K. O.; Pickett, R. B.; Vandenberg Air Force Base (International Foundation for Telemetering, 1974-10)
      This paper describes an improved tape recorder signature using pseudorandom PCM data. The use of the signature for telemetry ground station validation is discussed. Advantages over other techniques in common use are shown.
    • The Future of Real Time Telemetry Systems

      LeCann, Raymond P.; Grumman Data Systems Corporation (International Foundation for Telemetering, 1974-10)
      This paper briefly outlines the development of real time data processing systems and discusses the techniques used in present systems to bring full power of computer facilities to the systems user. While discussing existing systems, future user requirements are examined and the application of recent technology to these needs is investigated. Software systems, hardware techniques and systems management are reviewed so that future systems design may be responsive to the human, as well as the technical elements of vehicle testing.
    • Performance of Noncoherent MFSK Channels with Coding

      Butman, S. A.; Lyon, R. F.; California Institute of Technology (International Foundation for Telemetering, 1974-10)
      Computer simulation of data transmission over a noncoherent channel with predetection signal-to-noise ratio ST/N₀ = 1 shows that convolutional coding can reduce the energy requirement by 4.5 dB at a bit error rate of 0.001. The effects of receiver quantization and choice of number of tones are analyzed; nearly optimum performance is attained with eight quantization levels and sixteen tones at ST/N₀ = 1. The effects of changing ST/N₀ are also analyzed; for lower ST/N₀, accurate extrapolations can be made from the data, but for higher ST/N₀ the results are more complicated. These analyses will be useful in designing telemetry systems when coherence is limited by turbulence in the signal propagation medium or oscillator instability.