• The Helios Spacecraft/Ground Telecommunications System Concept

      Hertlein, H. P.; Gesellschaft fuer Weltraumforschung (International Foundation for Telemetering, 1974-10)
      The U. S.-German joint Helios Program is briefly presented with emphasis upon the Spacecraft Telecommunications System design and Ground Tracking and Data System. The design constraints for the radio system, and some tradeoff considerations germane to the Helios radio system are discussed. The block diagram, major performance parameters and some test results are given as bases for the understanding of more detailed telecommunications system discussions.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • Atmospheric Monitoring Using Infrared Heterodyne Radiometry

      Peyton, Bernard J.; Cutler-Hammer (International Foundation for Telemetering, 1974-10)
      Atmospheric constituents have unique vibrational-rotational signature lines within the infrared spectrum and the signature intensities and line shapes vary with the constituent concentration and the atmospheric density. The recent development of stable, single frequency, single-mode laser local oscillators and nearly quantum-noise-limited heterodyne receivers have permitted the development of infrared heterodyne radiometers (IHR's) which provide good sensitivity and excellent specificity for the remote examination of individual atmospheric constituent signature lines. A 9 to 11 μm IHR employing a CO₂ laser local oscillator has been developed and can be used to resolve the spectral signature of atmospheric constituents such as SO₂, O₃ C₂H₄, and NH₃. The IHR has a bandwidth of 100 MHz (33 x 10⁻³ cm⁻¹) and a minimum detectable power spectral density of 5.4 x 10⁻²⁴ W/Hz for a 1-second integration time. For atmospheric monitoring applications the IHR telescope collects the thermal energy radiating from the earth at: (1) a clear spectral window, and (2) a spectral region in which the signature lines of the constituent gases at various layers of the atmosphere will be energized by the upwelling thermal radiation. When the vertical temperature distribution of the atmosphere is known, the concentration of the atmospheric constituent gas can be determined as a function of altitude from the radiance data collected at the IHR using an iterative mathematical technique.
    • 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.
    • Adaptive Bit Synchronizer

      Halpern, Peter H. (International Foundation for Telemetering, 1974-10)
      The motivation for adapting loop bandwidth is reviewed. The ideal loopwidth is shown to be a monotonic function of the ratio of two statistical measurements, namely the input SNR and the present uncertainty of proper phase. This is seen from a relatively simple viewpoint of how to combine independent measurements of the same quantity. Means for measuring the statistical quantities are described. Simple means for varying loop widths are described. Experimental results of the adaptive bit synchronizer are compared with a classical bit synchronizer.
    • 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.
    • 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.
    • Volunteer Medical Engineers Can Aid Physicians and Hospitals in Telemetry Purchases and Tests

      Jackman, K. R. (International Foundation for Telemetering, 1974-10)
      Inasmuch as this 'ITC/USA/’74’ paper may be on a unique subject in the medical field, an attempt will be made to cover, with references and bibliography, sufficient background to identify some serious hospital and medical problems, with possible technical solutions. Most of these solutions involve the use of trained and experienced Medical (or Clinical) Engineers and Biomedical Equipment Technicians (BMET) in hospitals, clinics, and equipment servicing laboratories. The use of volunteer 'Med. Engrs’, as a public-service of the ACTION groups in each city, will be proposed to solve the local hospital needs for technical performance specifications in purchasing 'vital’ medical instruments, such as the 'ECG’ telemetry systems common to local hospitals. Even greater need for low-cost medical-care exists in many 'developing’ countries, such as India. The writer makes a plea, using Med. Engrs. methods developed and successfully used in Los Angeles in the last three-years, to bring graduate (medically-oriented and trained) engineers, seeking employment into hospitals in their own towns. A 'pilot’ program will be reviewed, using 'ACTION’ professional volunteers in San Diego hospitals, to set an example for 'Med.Engrs’ retrained in Madras, India, to enter their local hospitals, and thereby select techniques for use in other Indian cities.
    • Flexibility Objectives for Real-Time Telemetry Processing Systems

      Rymer, J. W.; Naval Air Test Center (International Foundation for Telemetering, 1974-10)
      A generalized real-time telemetry processing system model is developed in four blocks: Demod/Synchronization, Data Channel, Processing/Control and Display. Flexibility objectives are stated for each block and illustrated with respect to the Navy's existing Real-time Telemetry Processing System (RTPS). Features and tradeoffs are discussed for each block along with references to the growing and significant body of such systems already existing and currently under development.
    • The Shallow Sea-A New Challenge to Telemetry and Communication

      Werner, Edgar; Inter American University of Puerto Rico (International Foundation for Telemetering, 1974-10)
      A preliminary study of the environmental and operational parameters requisite to the design and development of low cost simplified communication and telemetry devices usable in the shallow waters of continental shelves is presented. Specific requirements peculiar to the needs of Ocean Resource Utilization Programs in underdeveloped countries lacking both economic and technological capabilities for using current off the shelf devices are outlined. The environment in which this equipment must operate is defined, first physically and then subjectively, and operational aspects of this type of endeavor are described in terms of the individuals involved. Finally, some design parameters are suggested with a general consideration of the potential market as these programs increase in scope and number. It is hoped that feedback from this paper will generate future specific designs and quantitative criteria on which to base more detailed development work.
    • An S-Band Telemetry Receiver System for Deep Space Applications

      Lampert, E.; Siemens AG (International Foundation for Telemetering, 1974-10)
      To receive the transmitted signals from the HELIOS space probe a S-band telemetry receiver system was built. Of this system the S-band telemetry receivers and the subcarrier demodulators are described. Measured values are presented. The S-band receiver includes a digitally implemented phase-locked-loop. Polarization tracking is possible in a two channel mode as well as in a single channel mode. In the subcarrier demodulator the subcarrier is demodulated before demodulating the RF-carrier. Good noise thresholds and low degradation is reached because remodulation is used in the subcarrier loop. The equipment works in a fully computer controlled station, this includes all aquisition procedures.
    • Computer Controlled Radio Information System for Public Vehicle Operations

      Go, G. Bie; AEG-Telefunken (International Foundation for Telemetering, 1974-10)
      Radio control centers for Public vehicle operations has long been an essential instrument to control and monitor schedules and operations. However, due to the rapid development of city and urban traffic the capacity limit of the small amount of voice channels is already reached, especially during rush hours. Moreover the dispatchers are overburdened, so that adherence to schedule and safe operations cannot be guaranteed. Data communications is the means to increase the efficiency and the capacity of the existing system. AEG-TELEFUNKEN has conceived an advanced system TELETRANS utilizing computer control and radio monitoring. This system makes improved use of the existing channel capacity without infringing on current FCC regulations. Through the use of co-channel transmission, which is a special type of transmit diversity, large areas with diameters up to 40 km (25 mi.) can be covered. This system is flexible, so that requirements of small and large public transportation authorities can be fulfilled economically.
    • Telemetry in Underground Mines Using Leaky Transmission Line Nets

      Hu, A. H.; New Mexico State University (International Foundation for Telemetering, 1974-10)
      A wayside underground communication system using leaky electromagnetic transmission line nets is presented in this paper. This leaky line or cable enables radio wave propagation through tunnels and out-of-sight places via combined cable and atmospheric transmission. It is also an all-purpose communication link which provides telemetry, communication, traffic control, emergency capabilities, paging, TV surveillance, fire detection, and fire control.
    • German Telecommand Station-The Dynamic Behaviour of the Steel Structure and Its Drive and Control System

      Eschenauer, H. A.; Schwarz, R. K.; Krupp Industrie- und Stahlbau; Siemens AG, Unternehmensbereich Energietechnik (International Foundation for Telemetering, 1974-10)
      The mechanical equipment and steel structure of large antennas represents a vibratory system made up of very many elastically coupled masses. Together with the drive control equipment, this complex system has to meet certain requirements with regard to pointing accuracy, turning range, turning speed, and acceleration. Prior knowledge of the dynamic behaviour of the whole control loop is essential to avoid unpleasant surprises at the commissioning stage.
    • Comparison of Viterbi and Sequential Decoding with a Noisy Carrier Reference

      Hofman, L. B.; Lumb, D. R.; NASA Ames Research Center (International Foundation for Telemetering, 1974-10)
      Performance of convolutionally encoded telemetry systems with Viterbi decoding or sequential decoding is well understood for the additive white Gaussian noise channel with coherent detection of bi-phase-shift-keyed signals. Significant degradation from ideal performance can occur due to correlated noise resulting from low signal-to-noise ratios in the receiver carrier tracking phase-locked loop. Performance at the lower telemetry data rates on the two Pioneer Jupiter deep space probes provides examples of the effect of correlated noise on a sequential decoding system. Performance degradation needs to be quantified as a function of carrier signal-to-noise ratio (P(c)/N(o)2B(lo)) and carrier-tracking- loop-bandwidth-to-symbol-rate ratio (B(l)/R(s)) in order to provide design and analysis information on such effects. Analytical modeling is extremely difficult, particularly where B(l)/R(s) is neither very large nor very small.
    • Some Simulation Results for Convolutional Codes Over a PCM/FM Fading Channel

      Grant, T. L.; Hofman, L.; NASA Ames Research Center (International Foundation for Telemetering, 1974-10)
      NASA is now actively planning entry probe missions for the outer planets. Such an entry probe requires a new telemetry link design. A probable modulation for this link is a continuous phase, narrow-band FSK (or PCM/FM), and this paper reports on simulations which can be used to estimate convolutional code performance with mild fading on such a channel. Simulated decoding has been performed for a range of signal-to-noise ratios on the PCM/FM channel with various fading characteristics.