• International Telemetering Conference Proceedings, Volume 05 (1969)

      International Foundation for Telemetering, 1969-09
    • A Flexible Format Adaptive Telemetry Encoder

      Communications Satellite Corporation (International Foundation for Telemetering, 1969-09)
      The Communications Satellite Corporation is developing the systems design and implementation techniques for a flexible format adaptive telemetry encoder. The encoder design includes wired program options to tailor system capability to mission requirements. on-board data source controlled interrupt of the normal telemetry format for transmission of preprocessed or block accumulated information automatically adapts the telemetry channel to variable data rate sources. Ground command control format modifications provide increased data rate or continuous burst readout of selected data inputs. Distributed commutation is also available for the remote collection of analog and digital data. Extensive use is made of monolithic MSI MOS devices and custom hybrid bi-polar logic arrays in the instrumentation of the encoder.
    • 10.6 Micron Laser Communication Experiment for ATS-F and ATS-G

      McElroy, J. H.; Richards, H. L.; McAvoy, N.; McGunigal, T. E.; Richards, W. E.; Yagelowich, H.; NASA Goddard Space Center (International Foundation for Telemetering, 1969-09)
      A laser communication system weighing 30 pounds and consuming 30 watts is to be flown on the ATS-F satellite for a space-to-ground experiment. An identical system proposed to be flown on ATS-G will complete an experimental intersatellite communication link. A 6-inch aperture optical antenna with a 92 dB antenna gain and a 500 mw carrier provide a minimum 23dB carrier-to-noise ratio for a 5 MHz bandwidth system. This experiment will permit analysis of laser Communication system parameters as a base line for future operational system designs, such as could be employed on a Data Relay Satellite. In addition to the NASA ground station, a station prepared by Bell Telephone Laboratories will perform atmospheric propagation experiments on the beam received from the satellite.
    • A New Bandlimited M-ARY Non-Coherent Telemetry System

      Stone, M. S.; TRW Systems Group (International Foundation for Telemetering, 1969-09)
      In this paper new M-ary non-coherent signal structures that require less transmission bandwidth than conventional FSK are presented. A method of synthesizing these signal sets by the use of frequencies or tones is given. In order to evaluate system performance, an approximation to the error probability for large signal energy-to-noise spectral density ratio is derived. Using this formula certain signal structures are evaluated for M = 8, 16, and 32. It is shown that for error rates of less than 1 x 10⁻³, the signal structures that reduce the transmission bandwidth by 25% are within 1 dB of the corresponding FSK signal set. Thus these signal structures provide an efficient method of communication when the bandwidth is constrained to be less than required for the transmission of FSK.
    • Filtering Effects in a Spread-Spectrum Telemetry System

      Harman, W. H.; TRW Systems Group (International Foundation for Telemetering, 1969-09)
      Binary antipodal direct-sequence biphase modulation is employed (for the purpose of interference reduction) over a channel disturbed by white noise and an "external" coherent sinusoidal interference. Before these are added, the signal suffers distortion in the form of linear filtering whose effects are to be determined. The receiver is a coherent "rematched filter" (matched to the distorted signal). The mean and variance of the detection variable are expressed as an output SNR (signal to noise ratio). The variance is the sum of three components: due to noise, external interference, and self interference. Concise formulas for the first two contributions are developed. The third is approximated and found to be quite small in many cases of interest. Results are applied in the case in which the filter has a bandpass characteristic and external interference is dominant. With fixed signal power entering the filter, there is an optimal chip rate above which filter distortion effects increase faster than process gain; the optimal chip rate is approximately equal to the filter noise bandwidth B (Hertz). For an ideal bandpass filter and a single pole bandpass filter, the optimal chip rates are 1.0B and 0.95B, respectively.
    • Stored Program Decommutation Techniques

      Galpin, R. J.; Mabe, R. C.; IBM Corporation (International Foundation for Telemetering, 1969-09)
      The application of core storage elements directly in the ground station data path could add greatly to the solution of increasing telemetry input data load problems. Decommutator control information loaded into these elements at mission set up time allows complete front end control by the main processor. Indeed, more complex formats such as PCM sub-subframes could be handled, depending only on the extent and sophistication of the control routine. Prestoring FM muliplexer addresses on prescribed sequences with a selectable rate clock can provide a discriminator sampling scheme approaching the theoretical in terms of sample rates relating to signal frequencies. The data content is again only limited by the degree of sophistication of the control program. In general, these control programs are just extensions of the main processor. By using storage devices external to the processor, however, the dynamic decommutation can be performed in a fairly optimum manner without the high I/O data transfer from the computer. A second function provided by the core memory in the telemetry data stream is data identification. Particular preassigned bits stored with the control information can be attached to the telemetry data word as this word is transferred from the front end. These flag bits can be used to route the particular sample to the main processor or to display equipment for quick look purposes. Unique flag bits may also be used to key any special data handling required on that particular sample, such as attaching a time tag or selecting a special subroutine in the main processor.
    • Wideband Fiberoptic Analog Information Link

      Avicola, K.; Churchill, R. A.; Union Carbide Corporation; North American Rockwell (International Foundation for Telemetering, 1969-09)
      A high frequency data transmission system which is unaffected by high energy electromagnetic fields is described. The system utilizes a gallium arsenide (GaAs) infrared light emitting diode as the transmitting source, a glass fiber optic light guide as the transmitting medium, and a photomultiplier tube (PMT) as the optical receiving sensor. The photomultiplier output is displayed on a real-time wideband oscilloscope where it is permanently recorded on film. The overall system concept was chosen and each major component type was evaluated for optimum performance in this application. It was determined during the feasibility phase of the program that cryogenic cooling of the GaAs diode would be necessary to obtain high frequency response and high signal to noise ratio (SNR). Liquid nitrogen (LN₂) was chosen as the cryogen due to its low temperature, low cost, availability, and relatively long holding time. The described system results in a 40-ft fiber optic, analog data link with a frequency response of 80 MHz and a dynamic range of 32 db. The system is not susceptible to electromagnetic fields.
    • Biotelemetry of EKG Signals Within a Small, Closed Chamber

      Carpenter, F. C., Jr.; McDonnell Douglass Astronautics Company (International Foundation for Telemetering, 1969-09)
      A requirement arose for reliably telemetering EKG data from personnel within a closed metallic chamber to a receiver also located within the chamber. Although there is much information in the literature on biomedical telemetry, it generally deals with propagation of telemetry signals in the clinical laboratory or the field; little, if any, pertains to the problem at hand. Analysis of the environment showed that mathematical prediction of the propagation characteristics of the chamber would be difficult, if not impossible, due to its odd interior configuration. An empirical approach was taken. Several system approaches were considered; an FM/AM system and an FM/FM system were built and each evaluated in the actual environment. Data are presented on test results. A successful system is discussed, including a description of the receiving antenna network employed to ensure reception of the transmitted signals regardless of the location of personnel within the chamber. Conclusions regarding the chamber characteristics are given.
    • Application of Non-Linear Encoding to Picture Transmission

      Gardenhire, Lawrence W.; Radiation, Inc. (International Foundation for Telemetering, 1969-09)
      The process of converting nonlinear analog signals to linear digital signals is a type of companding. This process of companding consists of compressing or expanding the dynamic range at the transmitter and restoring the original levels at the receiver. In telephony it is used to account for differences in speakers' voices. A loud voice will not overdrive the channel, yet a soft voice can be heard. In image transmission and processing, companding is even more important because of the nature of image forming. Both natural and photographic image formation are multiplicative processes. In a natural scene, the illumination and reflectance of objects are combined by multiplication to form observable brightness. Since this combining is a nonlinear process, it is important to transform the output to a linear signal at the earliest possible point in the transmission. If linearizing is not done, noise will affect the dark portion of the picture much more than the bright areas. Companding can be accomplished in many ways either by analog or digital method. The most common analog method is the use of log amplifiers with nonlinear amplitude gain. The most common digital technique is nonlinear encoding which performs the companding while the analog signal is being converted to digits. This companding process, when used on the output of a photo scanner, can be used to improve the transmission and reconstruction of digital pictures.
    • Permutation and Circuland Matrices and the Fast Fourier Transform

      Heenan, N. I.; The Mitre Corporation (International Foundation for Telemetering, 1969-09)
      This paper provides a description of the Fast Fourier Transform and its connection with the circulant and permutation matrices. It is written for the case where the number of discrete time samples is equal to the number of discrete frequency samples but is otherwise not restricted. The paper demonstrates that since the modal matrix of a permutation matrix contains only one bit of information, the evaluation of the discrete Fourier Transform involves considerably fewer than N² multiplications where N is the number of samples involved and is also the order of the matrices involved.
    • MAP, A Modular Design Concept for Recoverable Scientific Rocket-Borne Experiments

      Wright, W. W.; Southwest Center for Advanced Studies (International Foundation for Telemetering, 1969-09)
      A series of scientific payloads have been built and flown aboard Nike Apache Rockets. During the design phase heavy emphasis was placed upon realizing a modular configuration both structurally and electrically. The payload was divided into two sections according to functions. The support section included such things as telemetry, batteries, power supplies, timing, aspect sensing and programming facilities. The experiment section was composed of six independent experiments each provided by a different group. Each experiment was built to conform to the shape factor, and electrical requirements of the payload. This paper will discuss the modular nature of the experiments only. The theoretical and instrumental features of the different experimental problems are to be published in other literature along with the research results from the 1969 flight program. The features of the support system which make for maximum modularity will be emphasized in this paper.
    • Low Cost Water Quality Monitoring by Radio Telemetry

      Woffinden, D. S.; Kartchner, A. D.; Utah Water Research Laboratory, USU (International Foundation for Telemetering, 1969-09)
      A radio telemetry water quality monitoring system has been designed and constructed at the Utah Water Research Laboratory (UWRL). The system consists of a central base station at the laboratory and remote field stations located in the river to be studied. The remote field stations operate in the stand-by mode until interrogated from the central base station. Each station is capable of monitoring dissolved oxygen (D. O.), hydrogen ion concentration (pH), electrical conductivity, and temperature. Other variables could be monitored by using appropriate sensors. The prime features that characterize the UWRL system are low cost and relatively small size. These are both realized through the use of printed circuit boards and integrated circuit amplifiers. The remote station is small enough to be portable and can be installed either permanently or temporarily at almost any river location with a minimum of effort. Such a system, costing about $3,000 per field site, will make feasible the monitoring of water quality at points which previously were uneconomical to investigate.
    • Why Data System Standards

      Poland, W. B., Jr.; Fitzgerald, R. T.; Coates, R. J.; NASA Goddard Space Center (International Foundation for Telemetering, 1969-09)
      This paper discusses some ideas about data system standards which have been developed at the Goddard Space Flight Center (GSFC) of NASA over a period of about nine years, mainly as the result of experience gained in using the Space Tracking and Data Acquisition Network (STADAN), a collection of tracking, command, and telemetry stations for ground support of scientific satellites. The authors have found that the purposes and uses of data system standards are often misunderstood. To aid in clarifying this situation, they have described the growth and current implementation of the working approach to standards at GSFC. This approach is conditioned by the operating environment and by a number of administrative decisions, which are discussed. The areas included in the existing GSFC standards and some of those planned for future coverage are described, and some considerations bearing on the feasibility of combining GSFC and other data system standards are examined.
    • Frequency Diversity for UHF Telemetry

      Lilienkamp, Hugh; Naval Avionics Facility (International Foundation for Telemetering, 1969-09)
      This paper describes the function and design of the CV-2138 (XAN-1) UHF Down Converter developed at the Naval Avionics Facility, Indianapolis, Indiana. This unit is part of the Navy's Tartar, Terrier, Talos missile UHF telemetry/miss-distance information (MDI) system AN/SKQ-2 (XAN-1) now under development at this Facility. The converter, a dual-channel unit, receives signals in the 2200-2290 MHz and 1760-to-1850 MHz bands, and produces IF's of 240-330 MHz and 110-200 MHz respectively. The 1960 MHz local oscillator (LO) frequency, common to both channels, is supplied from a single source.
    • A 17:1 Dual Band Circularly Polarized Focused Two-Channel Monopulse Tracking System

      Lantz, Paul A.; Chadwick, George G.; Hurlburt, Roderic W.; Yaminy, Roger R.; NASA Goddard Space Center; Radiation Systems, Incorporated (International Foundation for Telemetering, 1969-09)
      This paper describes a dual circularly polarized feed system for operation In incremental bands over the frequency range from 136 to 2300 MHz. The characteristics of a 60-foot parabola excited by the feed system are discussed. Tracking data for this system have also been obtained using a helicopter, the Apollo VIII vehicle, and Cassiopeia A. It will be shown that the two-channel monopulse technique allows the use of antenna feeds which, in turn, provide sidelobes of greater than -20 db relative to the main lobe peak for all frequencies. This sidelobe performance reflects the fact that the feed is approximately focused at all frequencies, unlike its earlier log periodic type predecessors. The characteristics of a similar feed used in the Apollo Range Instrumented Aircraft (A/RIA) will also be described in this paper.
    • Tracking and Data Relay Satellite Systems

      Baritt, P. F.; Andrus, A. M. G.; NASA (International Foundation for Telemetering, 1969-09)
      As a result of three years of study, it has been determined that implementation of a Tracking and Data Relay Satellite System (TDRSS), using satellites in synchronous orbit to relay data between low altitude earth orbital spacecraft (both manned and automated) and the various mission control centers could improve the capabilities of the NASA tracking and data acquisition networks. Such a system, by providing nearly continuous, real time access to low altitude spacecraft, would improve mission reliability; contribute immeasureably to the safety and morale of the crews of manned spacecraft; permit real time command and control of automated spacecraft, making their operation more versatile; enable experimenters to monitor their experiments in real time, perhaps thereby reducing the workload on data processing facilities; and, in general, relieve constraints upon mission planning and operations that are imposed by the short duration, intermittent contacts characteristic of ground based T&DA facilities. Furthermore, studies indicate that this improved T&DA system will probably present networks that it could pay operation. The benefits outlined above are an operational TDRSS consisting of ground stations. If initiation of commence in FY-1971, the launch of cost sufficiently less to operate than for itself within a few years of realizable upon the implementation of three satellites and their supporting the development of the system could the first two data relay satellites would be possible by CY-1974. Allowing for a thorough system checkout and evaluation, during which time the remaining satellites would be launched, a TDRSS could become operational by the end of CY-1975.
    • Antenna Pattern Analysis - A Computer Model

      Wolff, F. M.; Atlantic Research Corporation (International Foundation for Telemetering, 1969-09)
      This paper describes a digital computer program which is used to calculate certain performance parameters for a telemetry antenna on a flight vehicle. Ground tests of the antenna, or its mockup, are performed and readings taken of the observed gains. This gain pattern is in the form of paper tape which is converted to a computer, acceptable punched are format. The program was written for the IBM 360/65 computer operating under multiprogramming with a variable number of tasks. A visual representation of the pattern is presented and radar tracking site information is displayed in tabular form. Examples of predicted data and flight data are shown.
    • Apollo ExtraVehicular Communication Telemetry Subsystem

      Weippert, J. J.; Donaghy, R. E.; Sonex, Incorporated (International Foundation for Telemetering, 1969-09)
      The original Apollo Space Suit Communications System (SCC) was designed to accommodate one Extravehicular Astronaut. Early in 1967, NAS.N established a requirement for an extravehicular Communications System (EVCS) which would enable two astronauts to simultaneously explore the lunar surface. Included in this requirement was a telemetry subsystem to monitor the performance of the portable life support system (PLSS), space suit performance and body functions of each astronaut while on the lunar surface. This paper reviews the EVCS telemetry subsystem design including electrical and functional capability, packaging techniques, reliability and configuration control programs utilized in meeting the stringent requirements of a miniature, high reliability, man-rated electronic system for space applications.
    • RFI Characteristics of a Data Relay Satellite System

      Bryan, John W.; NASA Goddard Space Center (International Foundation for Telemetering, 1969-09)
      The use of geosynchronous satellites for relay of data from near earth orbiting satellites is being considered by NASA. Since these relay satellites will have directional antennas beamed toward the earth at all times any earth based emitter is a potential source of radio frequency interference (RFI). An investigation has been made in an effort to determine the magnitude of this interference. The information presented here is based upon known frequency assignments and known equipment capabilities. All data and analysis presented are for the continental U. S. only and in some respects depicts a bleak picture.
    • Frequency Diversity for UHF Telemetry

      Kinkead, W. K.; General Electric Company (International Foundation for Telemetering, 1969-09)
      The use of frequency diversity to allow substantial airborne antenna simplification for L and S band telemetry is described. The system is particularly useful on large, spin stabilized vehicles where omni-directional antenna coverage is required. Typical antenna patterns with and without diversity are presented. A systems block diagram showing dual receivers and diversity combiner is also described. A weight tradeoff is presented for diversity versus non-diversity, with vehicle diameter (at the antenna location) as the variable. It is shown that, at S band, for diameters in excess of about 5 in., frequency diversity represents a favorable approach.