• 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.
    • A Transponder for Deep Space Probes-Design and Performance Characteristics

      Go, G. Bie; AEG-Telefunken (International Foundation for Telemetering, 1974-10)
      Deep space probes necessitate the use of coherent ranging transponders. The requirements for this class of transponder can be divided into telemetry, command and ranging requirements. Usually the telemetry requirements are rather straightforward and concern more with hardware design aspects. On the other hand, command requirements generally requires iterative computations to achieve an optimum system design. Ranging requirements are based either on a simple turn-around ranging channel, or on the complex regenerative channel. The design of this transponder is based on the former type of ranging channel. This paper shows the system design for such a transponder and a comparison with measured performance characteristics. Additionally, spurious signal analysis for the ranging operation is dealt with briefly.
    • The Data Handling System of the Helios Probes

      Pabst, Dietrich; Digital Space Applications (International Foundation for Telemetering, 1974-10)
      The Helios probes A and B will have a maximum distance of 2AU from Earth. The typical requirements which are applicable to all deep space missions, especially decreasing link capacity, need a flexible data handling system. Taking the Helios probe as an example, it will be shown how the specific problems of data handling in deep space probes were solved from the technical standpoint. The system processes 4 selectable scientific formats at 8 to 4096 bit/sec with 320 subcommutated housekeeping channels, also to be transmitted in a separate engineering format. Simultaneously, a special format is stored cyclically with up to 16kbit in a 0.5Mbit memory, which can also be used for the storage of all the other data in an automatic sequence mode. Telemetry data are convolutional coded. Due to its flexibility and its multiplicity, the data handling system is a useful instrument for deep space missions.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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 oz.one concentrations which are encountered in most urban areas.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.