• A 200 Megabit Per Second Data Handling/Data Link Simulator

      Goodwin, John E.; Martin Marietta Aerospace (International Foundation for Telemetering, 1975-10)
      A multimegabit serial data channel, or slower parallel channels may be needed to monitor multiple input data (including video) from sources such as Earth Resources Experiments, Communication Satellites, and surveillance systems. It is desirable to operate space equipment at low power, which is contrary to the use of fast circuits. Low powered circuits are compatible with the speeds of parallel systems, but multiple channel RF systems are usually costly in both size and weight. A parallel series compromise appears to minimize these problems. A laboratory breadboard of a parallel-series data handling simulator consisting of a data acquisition unit (DAU), a 200 Mb/s serial data link (SDL), and a data recovery unit (DRU) was built and tested to operate satisfactorily up to 230 Mb/s in a typical noisy environment.
    • Advanced Communications Experiments for Spacelab

      Ehrlich, Eugene; NASA Headquarters (International Foundation for Telemetering, 1975-10)
      The joint NASA-ESA Spacelab project offers the space engineer the opportunity to develop and test advanced communications technology in a new environment. The large volume and weight carrying capability of the Spacelab, plus the presence of an astronaut-engineer, means that large-diameter deployable antennas can be developed; multiple antennas operating at differing frequencies can be employed for propagation experiments and the detection of radio frequency noise sources on earth; and comparative, side-by-side telemetry experiments can be performed employing differing modulation techniques. The zero-gravity, high altitude and frequent flights into space make Spacelab a new tool for the communication engineer to employ for telemetry/ communications research.
    • An Analog Memory Device

      Uzunoglu, Vasil; COMSAT Laboratories (International Foundation for Telemetering, 1975-10)
      The analog memory device is a combination of a bipolar and a MOSFET device which stores information in analog form for several hours or more with no degradation of data. The emitter base junction of a bipolar transistor is covered with an SiO₂ layer and a voltage is applied to this point. With zero volts applied, the unit acts as a bipolar transistor. Increasing the voltage at this point increases the emitter injection efficiency of the bipolar transistor, which in turn increases the current gain of the device. An SiO₂ layer with no leakage paths can retain the charge applied to it for long periods of time; thus the gain will remain at this level as long as the charge remains on the oxide layer. A large number of such devices can be fabricated on a single chip. Such devices combined with other integrated circuits can be used, for example, for automatic equalization of transmission lines, echo suppression, and correlation detection.
    • Appendix: Fourteenth Annual Report of the Telemetering Standards Coordination Committee

      Kortman, Cecil M. (International Foundation for Telemetering, 1975-10)
    • The Application of Fiber Optics to Army Communications

      Dworkin, Larry U.; Coryell, Louis A.; Dragoo, Robert E.; USAECOM (International Foundation for Telemetering, 1975-10)
      We will examine a broad class of army communications applications for optical waveguides. Of principal interest is the multimode low-loss fiber. The applications receiving primary attention are (a) a long haul time division cable (TDM) system, (b) local distribution cable used to connect telephone users to central switches within a command post. A cost trade-off analysis reveals a cost saving up to $3K/km of a fiber optic TDM cable system over a conventional metallic cable system now in the army inventory. A review of a feasibility model design that employs a low-loss ruggedized Corning fiber cable, with special sources and detectors designed for ECOM application, is conducted. The resulting cable facilities appear fully capable of meeting all aspects of army cabling requirements and possesses all of the traditional advantages of fiber optic transmission system.
    • Application of the LANDSAT Data Collection System in Alaska

      Anderson, Duwayne M.; McKim, Harlan L.; U.S. Army Cold Regions Research & Engg. Lab. (International Foundation for Telemetering, 1975-10)
      LANDSAT data collection platforms have been interfaced with a variety of environmental and water quality sensors to test performance, reliability and versatility of the LANDSAT data collection system. Signal conditioning interfaces were required for sensors selected to measure: ground, soil and air temperatures; wind passage and speed; snow accumulation and ablation; pore water pressures; salinity; pH; dissolved oxygen; and water stage. System performance was found to be excellent; system reliability was high. Considering technical aspects only, exploitation of this satellite system for automated environmental and water quality data collection is hindered most by the relatively immature state of sensor and interface development. Notwithstanding, well prepared, two man field parties had no difficulty in deploying DCPs with their associated antennae and sensor subsystems in remote subarctic locations. Environmental data acquired at the various sites are being used in the assessment of the environmental impacts associated with the proposed construction of two hydropower dams on the Susitna River in interior Alaska, on the effects of impoundments over permafrost, and in assessing the effects associated with the construction and operation of the trans-Alaska pipeline.
    • Architectures for Real-Time Digital Channel Simulators

      O'Grady, E. P.; University of Maryland (International Foundation for Telemetering, 1975-10)
      This paper suggests an all-digital, time domain approach for real-time simulation of digital communications channels and proposes four possible implementations of the time-domain approach using standard minicomputers or microprocessors and peripheral random number generators. The time-domain method is based on simulating the digital channel on a bits-in, bits-out basis with bit errors introduced into the bit stream in a manner which approximates the error sequence of a real (or hypothetical) communications channel. The error sequence of the simulator can duplicate a measured error sequence or it can be generated by a stochastic model of the error sequence. The four proposed implementations represent different levels of complexity in the architecture of the channel simulator. The first proposed implementation employs only a single computer; the second employs a computer and a peripheral random number generator; the third employs a computer and multiple peripheral random number generators; the fourth employs multiple computers and multiple peripheral random number generators. The significance of the time-domain approach lies in its potential application to the design of high performance, general-purpose media simulators at greatly reduced cost due to the use of standard hardware and relatively simple processing.
    • Asymptotic Performance of Three Hard-Limiting Noncoherent Correlator-Envelope Detectors

      Viterbi, Andrew J.; LINKABET Corp. (International Foundation for Telemetering, 1975-10)
      Three suboptimal correlator-envelope detectors are analyzed for the noncoherent detection of one of M signals. Suboptimality is introduced in each case by hard limiters which serve the dual purpose of providing automatic gain control (AGC) and simplifying mechanization. The first two, bandpass limiter preceding the detector and hard limiter in each channel, are well known and included for comparison. The third which is like the second, but with the additional feature of comparison weighting of the limiter outputs, is shown to exhibit an asymptotic performance within 0.25 dB of the bandpass limiter.
    • Atmospheric Propagation Effects on a Laser Ship Mast Detector

      Curtis, Harold O. (International Foundation for Telemetering, 1975-10)
      The performance of a laser gate ship mast detector is evaluated. The laser gate consists of transmitting optics and laser on one side of a shipping channel and receiving optics and detector on the other side of the channel. Expressions relating the probability of detection and the false alarm rate to laser power, noise, visibility or atmospheric attenuation of the beam are developed. Finally, at power levels meeting safety standards and for useful probabilities of detection and false alarm rates, the visibilities which limit system performance are determined as a function of laser gate path length. The gate, at visible wave lengths, will function at visibilities only slightly less than the path length. In the next step, the expected performance of the laser gate using a CO₂ laser radiating at 10.6μ in the infrared is analyzed. The extinction coefficient, which is only a fraction of that in the visible case, is estimated for poor visibility conditions (RVR = 1,000 ft.) from a combination of attenuation measurements relating attenuation to total water content and meterological results relating visibility to total water content. Then, for the infrared system, the same arguments as above are invoked and, in this case, it is shown that the infrared system will provide the required performance at much longer path lengths.
    • An Automated Local User Terminal for Data Collection

      Buckelew, Timothy D.; Army Corps of Engineers (International Foundation for Telemetering, 1975-10)
      The need for realtime hydrologic data for flood control reservoir regulation puts special demands on a data collection system, especially during storms when it is most needed. In an experiment to test the use of the LANDSAT satellite for flood control activities, New England Division, U.S. Army Corps of Engineers in cooperation with NASA is constructing a local user terminal for direct receipt of satellite-relayed data at Waltham, Massachusetts. This station, consisting of a 15 foot dish, tracking and receiving equipment, and a mini-computer, will be relatively simple, automatic, capable of running unattended two to three days, and will be protected against power failures by software restart features. Early operation will depend on Predicting the satellite's position, but software autotracking may be developed.
    • The Automatic Analysis of Aerial Photographic Data

      Chen, C. H.; Southeastern Mass. Univ. (International Foundation for Telemetering, 1975-10)
      As the volume of aerial photographic data increases in various applications, there is increasing demand for automated data analysis. Faster and larger computer alone is not the solution. In this paper effective and computationally efficient techniques for computer processing of the aerial photographic data are presented. They include: (1) picture data compression, (2) feature exttraction using the histograms of the original and sharpened pictures, (3) sequential target and classification, (4) threshold selection, and (5) Walsh power spectrum analysis. All of these techniques may be incorporated in a fully automated data analysis system to meet certain real-time on-line system requirement.
    • Charge Coupled Device (CCD) Analog Signal Processing

      White, Marvin H.; Westinghouse Defense & Electronic Systems Center (International Foundation for Telemetering, 1975-10)
      A discussion of the CCD basic building blocks for analog signal processing with particular emphasis on application for telemetry. Serial in/Serial out (SI/SO) blocks provide time base translation electrically alterable delay, and sequential TDM filters, Parallel In/Serial Out blocks are useful in time divisions multiplexing (TDM) and Serial In/Parallel Out blocks for variable tapped delay lines, filters and correlators. Combinations of the above linear or one-dimensional blocks provides two-dimensional arrays for filter banks, multiple correlators, etc. Particular telemetry applications are FM filters, Parallel Correlators, Matched Filters, Single Sideband Modulators and Adaptive line equalizers.
    • Command and Data System for an Undersea Dredge

      Linders, Thomas E.; Lockheed Missiles & Space Co. (International Foundation for Telemetering, 1975-10)
      By the use of commercial equipment whose original purpose was to provide alarm monitoring (fire and burglar) over telephone lines, a command and data system was constructed to control an undersea dredge. The system was designed around the Larse Corporation Data Communicators (trademark), and only a PAM multiplexer and a digital demultiplexer were added to make the system perform. The system requirements were analyzed, and only after the candidate design was agreed upon were the ideas put to paper. The system was designed in modules, with the various components grouped according to their function, to simplify interconnecting and test/checkout. The system has performed well, no component failures have occurred to date, and all data and command functions have worked as expected.
    • The Common Element Approach to Telemetry Processing Systems

      Karleskint, Daniel J.; Control Data Corporation (International Foundation for Telemetering, 1975-10)
      This paper postulates a complete computerized telemetry processing system which has only one basic hardware module as the system building block. A discussion of the technology incorporated in the system and its effect on systems cost and complexity is included.
    • Communications and Data Handling for the GSFC Modular Spacecraft

      Trevathan, Charles; GSFC Spacecraft Data Management Branch (International Foundation for Telemetering, 1975-10)
    • COMSAT General Ranging Equipment Development

      Onufry, Michael; Jankowski, Joseph A.; COMSAT Laboratories (International Foundation for Telemetering, 1975-10)
      The range to the spacecraft is an important parameter for determining the transfer and synchronous orbits. The ranging equipment developed for the COMSAT General TT&C earth stations uses a fixed-tone technique to determine the distance from the earth station antenna to the satellites. Specifically, the range is calculated from the round trip propagation delay, which is determined by measuring the phase shift in four coherent audio tones. This system is similar to the ranging equipment used at the INTELSAT earth stations. New integrated circuit (IC) technology has permitted individual tone transmission which was previously not available. The ranging tones are frequency modulated in both the up- and down-links in the INTELSAT system. However, in the COMSAT General system the tones are frequency modulated in the up-link and phase modulated in the down-link. Hence, new techniques are required to determine the phase shift of the earth station equipment.
    • Concentration of Binary FM Spectra

      Papantoni-Kazakos, P.; Rice University (International Foundation for Telemetering, 1975-10)
      The spectrum of a digital FM signal can be considered as an indicator of the resistance of the signal to distortions caused by band-limitation. The study in this paper is oriented toward the design of signaling pulses that will achieve an FM signal spectrum concentrated about the carrier frequency. Convenient spectrum expressions and general guarantees of optimality are found for binary FSK signals.
    • Convolutional Coding Techniques for Certain Quadratic Residual Codes

      Booth, Richard W. D.; Herro, Mark A; Solomon, Gustave; TRW Systems (International Foundation for Telemetering, 1975-10)
      The encoding and decoding of the extended Golay code and the (32, 16) quadratic residue code by convolutional coding techniques is discussed. The generation of the extended Golay code is described in detail. A modified version of the Viterbi algorithm for hard and soft decision decoding was implemented, and the simulation results are presented.
    • Correction of Burst Errors Containing Bit Slippages for Cyclic Block Codes

      Green, Edward P.; Goddard Space Flight Center of NASA (International Foundation for Telemetering, 1975-10)
      Conventional burst error correction techniques for (n,k) cyclic block codes cannot cope with the presence of bit slippages that frequently occur in conjunction with burst errors of the bit inversion variety. A technique is described to enable the correction of an (n,k) cyclic code subjected to a noise disturbance consisting of an arbitrary number of both bit deletions and bit inversions contained within a single error burst. An efficient implementation of a Burst/Deletion Correction Decoder is presented. Although bit insertion correction is conceptually similar to that of bit deletions, the decoder implementation for combined insertion and inversion correction within a burst is much more cumbersome. The probabilities of false correction are analyzed.
    • Data Collection Using Adaptive Phased Array

      Noji, T. T.; AIL (International Foundation for Telemetering, 1975-10)
      Adaptive Ground Implemented Phased Array or AGIPA provides a rapid and cost effective means to read out and interrogate a very large number of earth based sensors. AGIPA locates an array in space but locates all of its beam forming and beam steering network on the ground; thereby providing multiple high gain beams to be formed with minimal complexity in space. AGIPA offers: * Less total system cost by placing a high gain array on a central data collection system and reducing the cost of each of the thousands of sensors. * Rapid data collection due to electronic beam steering as well as through formation of multiple beams. * Nulling of unintentional RFI that can disable the entire data collection system.