• Application of Walsh Functions to Data Acquisition Systems

      Morton, Walter (International Foundation for Telemetering, 1966-10)
      The Walsh functions are considered with respect to the following system functions: 1. Concise signal representation. 2. Arithmetic operations. 3. Convolution and filtering. 4. Transfer function analysis. 5. Special measurements and functions: 5.1 Phase. 5.2 Digitally controlled function generator (DCFG). 5.3 Power density spectrum. 5.4 Correlation functions. The foregoing operations are required of equipment in the following areas of application: 1. Seismic data processing. 2. Hybrid data systems and simulation studies. 3. Special purpose Instrumentation.
    • Predetection Diversity Combiner

      Casson, William Holton; Defense Electronics, Inc. (International Foundation for Telemetering, 1966-10)
      Pre-detection diversity combining provides a number of advantages in telemetry data reception, particularly when used in conjunction with pre-detection recording equipment. These advantages include optimal ratio signal combining before pre-detection recording, pre-detection signal-to-noise ratio and threshold improvement, higher improvement in demodulated signal-to-noise ratio as compared with postdetection combining, and a number of operational simplifications, which are further enhanced when the combiner is used with dual channel receivers. Laboratory tests verify predicted performance. Additional quantitative field data is needed, but preliminary results indicate excellent performance, and no problems in maintaining phase lock have been experienced.
    • An Experimental Investigation of the Capture Performance of FM Receivers

      Castellano, A. J., Jr.; Data-Control Systems, Inc. (International Foundation for Telemetering, 1966-10)
      This paper reports on the investigation of the effect of telemetry receivers capture ratio on overall system accuracy. Receivers with normal and improved capture ratio were compared to evaluate the methods used to measure capture ratio, determine the effect of I-F filter characteristics on capture ratio, and establish the penalty of bandwidth and distortion results including waveforms, photographs and spectral diagrams for various values of co-channel interference.
    • Surveyor Spacecraft Telecommunications

      Rickman, Frank; Kirsten, Charles; Hughes Aircraft Company; Jet Propulsion Laboratory (International Foundation for Telemetering, 1966-10)
      Although the Surveyor program is five years old, very little concerning the on-board telecommunications has been recently printed. Because much interest has been stimulated by the recent very successful Surveyor I mission, it is believed that this descriptive article of the Surveyor telecommunications system will be of general interest. The paper is oriented toward actual subsystem implementation and performance, rather than the purely analytical presentation. The reliability and flexibility of the telecommunications is detailed with some attention being given to the operational redundancy and variety of data transmission modes available. A few of the major difficulties experienced during the design and qualifications of the telecommunications equipment are touched upon, with commentary on the solutions finally used. Pertinent mission data is discussed, with a brief presentation of some telemetered AGC: signals. Finally, a summary of the experiments run on the telecommunications subsystem, both in-flight and on the lunar surface, are presented. These experiments included a deliberate in-flight increase in the data rate above the analytically predicted level for an acceptable bit error rate, a mapping of the planar array antenna gain while on the lunar surface, voice transmission via the Surveyor transponder, and subsystem performance assessments. This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS7-100, sponsored by the National Aeronautics and Space Administration.
    • RF Intermodulation Characteristics of VHF Telemetry Preamplifiers and Receivers

      Jeske, Harold O.; Sandia Corporation (International Foundation for Telemetering, 1966-10)
      Tests have been conducted on ten preamps and six receivers to quantitatively determine their linear operating range. The range of linear operation was determined by the measurement of, or the effects of, intermodulation (IM) products that were produced by the simultaneous application of two input signals. Measurements were made at a frequency equal to twice the frequency of one signal source minus the frequency of the other signal source. Tests of the ten preamps, which included eight solid state units, indicated that their dynamic range varies from approximately 46 to 70 db. Since the IM products of interest vary as the cube of the input signal, the output IM products may vary over a 72 db range, between the preamps tested, for a given input condition. It was found, under the best conditions with some receivers, that their proper operation was prevented by the presence of two signals that were less than 30 db larger than the desired signal. The two interfering signals were located well outside the rated - 60 db bandwidth of the receiver. The results of the tests should provide receiving system designers and operators with a better insight into the problem of RF intermodulation interference. Since no known military interference specifications consider intermodulation as investigated, it is believed that some standard test procedures should be developed by the telemetering community for preamp and receiver testing.
    • Polarization-Diversity Telemetry Receivers

      McCann, R. P.; Jones, R. D.; Sandia Corporation (International Foundation for Telemetering, 1966-10)
      Studies at the Langley Research Center of the National Aeronautics and Space Administration have shown that certain physical properties of extraterrestrial surfaces can be determined by analysis of impact-acceleration, time-history signatures obtained by instrumented projectiles (penetrometers). This paper considers the theory and design of a polarization-diversity receiver developed to receive and combine FM/FM penetrometer telemetry data. The signals are radiated by a set of orthogonal magnetic dipoles fed in time quadrature to obtain an omnidirectional radiation pattern similar to the pattern from a conventional turnstile. A special polarization-diversity receiving system is required to reduce the effects of fading of the RF carrier resulting from random changes in the orientation of the radiating antenna system. Various combining techniques are evaluated. Finally, a maximal-ratio, postdetection, dual-channel receiver with dual conversion and subcarrier discrimination developed specifically for the application is described.
    • Computer Controlled Telemetry Station

      Strock, O. J.; Defense Electronics, Inc. (International Foundation for Telemetering, 1966-10)
      A telemetry ground station under complete operational control of a general-purpose digital computer is described. The six subsystems which comprise the station are examined in some detail to show the method of control and the flexibility and speed of operation. A specific application is described and other potential applications are explored.
    • Error Detection and error Correction Under the Conditions of Quarternary Decision Logic Techniques

      Brothman, A.; Yanis, C.; Halpern, S. J.; Miller, A. H.; Sangamo Electric Company (International Foundation for Telemetering, 1966-10)
      The hardware and theory of a multi-threshold bit decision technique called Quarternary Decision Logic are described. Quartenary Bit Decision Logic results in two simultaneous decisions on each received bit of a binary digital transmission: (1) a binary status decision; and, (2) a reliability decision which reflects on the presence/absence of multilation in the bit. Both decisions are based on a Shannon Integration of the received information over the whole bit interval. The ability to assess bit mutilation is then used to develop adjustable security-enforcing restraints on error correction and the receiving process itself. These restraints are developed by a Word Security Logic which keeps a "mutilation count" on each received word, The "mutilation count" per word results in a "Correction Permit/Inhibit" and a "Receiving Permit/Inhibit" output on each word. The "Correction Permit/ Inhibit" output bars error correction when the risk of a spurious correction is high. The "Receiving Permit/Inhibit” output blocks receiving when the risk of a direct evasion of security is high. The improvement in bit decision security and the improvements in security against spurious correction and direct evasions of Error detection are evaluated quantitatively in comparison to conventional single-threshold techniques, These improvements enable secure operation with lower redundancy coding systems because of the information gain which Quarternary Decision Logic provides. The possible contributions of Quarternary Decision Logic to self-adaptive data transmission systems and to automatic line equalization are explored in the section entitled "Conclusions".
    • Reconstructing a Serial Pulse Train from Parallel Data Recorded on Magnetic Tape

      Hadady, R. E.; Kinelogic Corporation (International Foundation for Telemetering, 1966-10)
      On-board data stores in deep-space probes, spacecraft, satellites, and aircraft, frequently require the extensive bit storage capability of a magnetic tape recorder. For compatibility with other systems, it is necessary in some cases to be able to reproduce the data in serial form at a synchronous rate. To take maximum advantage of the storage capability of magnetic tape, however, it is desirable in many instances to record the data in a parallel format; i.e., the technique used in magnetic tape recorders used with ground based computers. Reconstructing a serial pulse train with a synchronous bit rate from parallel data recorded on magnetic tape involves some problems which are peculiar to magnetic tape recording equipment. Variations in tape speed (flutter), dynamic skew (wobble) of tape as it passes over the record and playback heads and static skew of the data on the tape resulting from head gap scatter and mean gap azmuth alignment results in nonsynchronous data being generated during playback. To provide synchronous data output, it is therefore necessary to provide a buffer between the output of the magnetic tape recorder and the system accepting the data. Recorder characteristics are examined with respect to their effect on the degree of non-synchronism. Furthermore, the size and complexity of buffers necessary to provide synchronous output data is considered.
    • PCM Transmission with Minimum Mean-Square Error

      Clark, G. C.; Totty, R. E.; Radiation Incorporated (International Foundation for Telemetering, 1966-10)
      One source of error in PCM transmission of analog waveform is the bit errors made in the binary sequences representing a particular level. Using a mean-square error criterion, the contribution of this (channel) error to the overall reconstruction error is examined. In particular, general simplified error expressions are derived for arbitrary sequence assignments including error correcting coding. Results are given for the power gain resulting from use of several error correcting codes. The criterion used here is mean-square error (rather than word probability of error) and the coded sequence is constrained to occupy the same time interval as the uncoiled sequence.
    • Desired Telemetry System Characteristics for Shock, Vibration, and Acoustic Measurements

      Himielblau, Harry; Subcommittee G-5.9 on Telemetry Requirements; SAE Committee G-5 on Aerospace Shock & Vibration (International Foundation for Telemetering, 1966-10)
      For over a decade structural dynamicists and acousticians have registered general dissatisfaction concerning the limitations of telemetry systems, especially the insufficient number of channels and insufficient data bandwidths. To spell out the users' need for present and future telemetry, a representative group of dynamicists was organized under the SAE. Requirements for number of channels per flight, data bandwidths, minimum dynamic range (with stationary and transient data signals considered separately), certain accuracy, phase and other characteristics were established. The subcommittee is hopeful that this information will spur the telemetry community into developing and standardizing on new systems with superior characteristics.
    • Factors Limiting UHF Telemetry Systems Operation

      Gong, H.; Herman, R. T.; Konop, P. L.; The Mitre Corporation (International Foundation for Telemetering, 1966-10)
      Demands on the use of that portion of the radio spectrum from 225 MHz to 400 MHz for military tactical operations have made it necessary to vacate the VHF telemetry band from 215 MHz to 260 MHz by I January 1970 and to convert such operations to UHF telemetry bands from 1435 MHz to 1540 MHz and 2200 MHz to 2300 MHz. The environmental, physical, and practical limitations imposed on telemetry system performance when operation is moved from VHF to UHF are described in this paper. The topics which are discussed include path loss, multipath, flame plasma effects, expected Doppler shift and Doppler rates, natural noise limitation, UHF transmitter power and stability, receiving system noise figures, airborne antennas and ground antennas. UHF telemetry operation in support of missions for aircraft, ballistic, orbital, and deep-space vehicles is evaluated mainly through a comparison with similar operations at VHF. The results of this study show that there are no technological factors which limit the instrumentation of an adequate UHF conversion.
    • A Compatible Double Sideband/Single Sideband/Constant Bandwidth FM Telemetry System for Wideband Data

      Frost, W. O.; Emens, F. H.; Williams, R.; Marshall Space Flight Center (International Foundation for Telemetering, 1966-10)
      This paper reviews the telemetry problems involved in transmission of wideband phenomena such as shock, vibration, and acoustic measurements. Three approaches to this problem have recently received considerable attention from the telemetry community: SS/FM, DSB/FM, and constant bandwidth FM/FM. The relative capabilities and limitations of these three techniques are discussed and their S/N performance and r-f bandwidth utilization efficiency are compared. An arrangement whereby the three techniques may be flexibly intermixed on a single RF carrier is then described. Examination and consideration of the merits of this arrangement as a future standard telemetry technique is proposed.
    • The Apollo Launch Data System

      Quinn, M. J.; Nasa Manned Spacecraft Center (International Foundation for Telemetering, 1966-10)
      The development of the Apollo Launch Data Telemetry System, the real-time interface between the Merritt Island Launch Area (MILA) and the Mission Control Center-Houston (MCC-H), is reviewed from its beginning through the system planning stages, and then into the final hardware implementation.
    • Magnetic Recording of Radar Data

      Young, Ronald E.; Ampex Corporation (International Foundation for Telemetering, 1966-10)
      The methods presently utilized for magnetic recording of radar data are explained with reference to basic radar types. The PPI radar has a time continuous video signal and generally requires a transient free recorder of moderate data bandwidth. In addition, means must be provided to record the azimuth information in either synchro, sine-cosine or digital form. Such means are available and recommended approaches for each type of data are given. Time discontinuous radar such as the missile tracking monopulse group may utilize recorders normally designed for video service if certain pulse spacing criteria are observed. The wider data bandwidth of this type of signal makes the use of rotary head recorders mandatory. There are many applications for radar recording. Some of those described include operator training, debriefing and scoring and operational evaluation of the radar facility. The radar recorder can be a significant aid in data analysis for signature determination of satellites and planetary mapping. The radar recorder also furnishes a close facsimile of the operating radar signal for system evaluation when there are no targets to observe or when the main radar is shut down for any reason. As an illustration of the application of magnetic recording to the radar system an airborne data acquisition recorder is described along with a companion ground reproducer. These two units are presently in use in the evaluation of an airborne radar system and offer significant advantages over previously available recording equipment. The development of time base stable magnetic tape recorders capable of handling data bandwidth in excess of 5 MHz has added another facet to the instrumentation field - that of recording radar data on a real time basis for analysis at a later time. The discussion that follows illustrates the methods used in magnetic recording of radar data and cites a typical recording system.
    • Requirement for a Data Quality Assurance Program

      Nichols, M. H. (International Foundation for Telemetering, 1966-10)
      The requirement for a Data Quality Assurance Program for telemetry ground station operations is outlined. Examples are given for frequency division and time division formats to demonstrate that a practical and meaningful program is within the state-of-the-art and in fact that the basic modules have already been developed for commercial communication systems. A program is recommended for expansion of the IRIG Standards to include performance criteria and specifications of end-to-end ground station tests for determining that the criteria are satisfied for each mission.
    • Telemetry System Design for Saturn Vehicles

      Frost, W. O.; Norvell, D. E.; Marshall Space Flight Center; The Boeing Company (International Foundation for Telemetering, 1966-10)
      This paper discusses the data system requirements for large space vehicles and describes a flexible telemetry system design which is used on all stages of the Saturn IB and Saturn V vehicles. The basic vehicle telemetry design provides standard assembly building blocks forming a versatile catalogue of parts from which a stage telemetry subsystem may be assembled to meet almost any conceivable monitoring requirement. In addition to its inflight monitoring function, the telemetry subsystem also provides real time data acquisition for automatic vehicle checkout.
    • Channel Noise - A Limiting Factor on the Performance of a Class of Adaptive Techniques

      Raga, Gerald L.; Electro-Mechanical Research Inc. (International Foundation for Telemetering, 1966-10)
      The effects of channel noise on a class of adaptive sampling techniques based on the concept of removal of redundant data samples were investigated. Assuming a system of fixed bandwidth and fixed transmitter power, the channel noise forces the adaptive system to operate at a lower bit error probability than the equivalent PGM system since in the adaptive system each transmitted bit represents more information. This limitation was partially overcome by adding error criterion of unequal weighting to the data which enabled the system to operate at essentially the same bit error probability as the PCM system with a net coding efficiency greater than the coding efficiency of the error-correction code. Experimental results from subjective tests, and the RMS error demonstrate that a new error criterion must be developed for the class of adaptive techniques.
    • New Concepts for Telemetry Converters

      Friend, Larry; Motorola, Inc. (International Foundation for Telemetering, 1966-10)
      Future requirements to convert present VHF telemetry receivers to L and S-bands can be satisfied by relatively simple solid state microwave converters. Use of the recently developed Schottky barrier diodes in balanced mixers along with high frequency field effect transistors in the intermediate frequency VHF preamplifiers, show considerable promise of providing low system noise figure (e.g. 5.5 dB) and low intermodulation distortion. These broadband converters have the potential advantages of minimum cost, size, weight, and power consumption, thereby providing a convenient and practical means for converting existing telemetry systems to the new frequency bands. Design considerations and predicted performance characteristics are presented for solid state converters of this type.
    • Low Level F. E.T. PAM Multicoder

      Gregory, Terence R.; General Devices, Inc. (International Foundation for Telemetering, 1966-10)
      This paper describes a new all solid state airborne low level PAM multicoder that employs N-channel FET for all the analog switching functions of the system. The unit features a 72KHz true chopper amplifier that affords complete isolation between input and output. This unit is fully developed and went into production in June 1966 offering many advanced features to airborne telemetry system users. Each input channel presents a true differential analog switch into the low level D. C. amplifier. The operating characteristics such as C. M. R. (100 db) out to 1KHz, no D. C. drift or gain-change, and selectable pedestal levels add to ease of operation and flexibility. Heavy use of integrated circuits was also made including monolythics, hybrids and discrete elements. The gating logic, chopper amplifier front end, and carrier amplifier/synchronous demodulator each have a separate power supply winding thus providing excellent isolation for user applications. Mechanical construction employs plug in boards affording ease of manufacture and complete interchangeability of boards between units. The system is discussed as to unique features and techniques necessary to build the unit and satisfy stringent specifications.