• A Telemetry Link for an Earth Penetrator

      Caffey, Thurlow W. H.; Sandia Laboratories (International Foundation for Telemetering, 1975-10)
      The design and field-testing of a telemetry link to send signals to the surface of the earth from an earth penetrator are described. The link uses a PCM/FM format at a frequency of 10.5 kHz, dissipates 8 watts, and fits within a cylinder with an inside diameter of 100 mm. A bit error rate of less than 10⁻⁵ was achieved from a depth of 52 meters at a bit rate of 10³ bits per second.
    • Low Frequency Telemetry from Terradynamic Vehicles

      Galbraith, L. K.; Sandia Labs. (International Foundation for Telemetering, 1975-10)
      A telemetry system has been designed and built which transmits digital data from a buried earth-penetrating vehicle to the surface by magnetic induction. The transmitting package is a cylinder 10 cm in diameter by 30 cm long and draws 5 watts of dc power while transmitting. Error rates of 1.16 x 10⁻⁴ have been obtained at a range of 52 meters through soil at a data rate of 50 bits/second, utilizing only the 0-50 Hz region of the electromagnetic spectrum. Projected performance of the system in high-conductivity media indicates useful ranges exceeding 50 meters in media as conductive as sea water (4 mho/meter). System improvements are discussed which should allow severalfold increases in data rate or range over the experimentally obtained values.
    • Microprocessor Controlled Thick-Film PCM Telemetry System

      Hakimoglu, Demirhan; Aydin Vector Division (International Foundation for Telemetering, 1975-10)
      This paper describes an approach to airborne PCM data acquisition that takes advantage of the latest technological advances in the fields of both the monolithic microcircuits and hybrid packaging. The result is a low cost system that provides a combination of long sought-after features; flexibility, modular make-up, microminiature size, high reliability and low power.
    • RPV Applications in the U.S. Navy

      Friichtenicht, R. D.; Naval Air System Command Headquarters (International Foundation for Telemetering, 1975-10)
      The continuing evolution to smaller, more reliable electronics packages has had a tremendous impact throughout industry and the world. One application that has just recently started receiving wide spread attention is Remotely Piloted vehicles (RPVS). The smaller computers, electro-optical devices, infra-red systems, etc. have brought the RPV out of its "model airplane" stage and into the military arena. RPVs offer some distinct advantages over manned aircraft, which places them in a very competitive position for accomplishment of selected missions. Cost savings promise to be significant and their comparatively small size make them attractive for operation from small naval ships. However, the Navy faces some unique problems that must be addressed before RPVs are an integral part of the Naval Forces. The most immediate and overriding problem is recovery. Not only is the recovery platform very small, but ship's movement through all three axis further complicates the problem. This paper discusses some of the possible naval applications of RPVs, and outlines the Navy's program for solving the recovery problem.
    • Use of Sonobuoys in Ocean Earthquake Studies

      Reichle, Michael; Bradner, Hugh; University of California (International Foundation for Telemetering, 1975-10)
      U.S. Navy anti-submarine-warfare telemetering sonobuoys have recently become an important tool in the study of earthquakes at sea. Earthquake ground motion converts to sub-audio compressional waves in the water and is detected by the sonabuoy hydrophones. The frequency-modulated sonobuoy signals are monitored with commercial VHF receivers on shipboard, aircraft or land, and are recorded on f.m. magnetic tape or strip chart. Subsequent analysis of the seismic signals gives information on location and depth of the earthquake as well as direction of fault motion, stress release and other characteristics of the event. The accuracy of epicenter location is usually limited by the precision of ship navigation but may also be limited by uncertainties in sonobuoy position measured from the ship. Events large enough to be detected on land have been located with better accuracy by sonobuoys than by the land arrays. This paper describes the techniques of using sonobuoys for earthquake research, and gives results of observations of microearthquake swarms in the Gulf of California along the extension of the San Andreas Fault.
    • Evaluation of a Random Access System with Hardware Simulation

      Delmas, G. G.; Centre National d’Etudes Spatiales (International Foundation for Telemetering, 1975-10)
      The purpose of this study is to solve the problem of the determination of the exact capacity and performances of a satellite location and data collection system using random access. Here is described the method we apply in the particular case of the ARGOS system; the TIROS-N and NOAA-A to G satellites will be equiped with the ARGOS on-board experiment and will ensure an operational service from 1978 to 1985 at least. The results we obtained are significantly better than the first estimations and should allow us to increase the number of the platforms.
    • 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.
    • 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.
    • Use of TSE Computers Aboard Spacecraft

      Schaefer, David A.; NASA-Goddard Space Flight Center (International Foundation for Telemetering, 1975-10)
      The Goddard Space Flight Center has undertaken a program to develop improved methods of handling two-dimensional data. From this, the concept of a new family of computers known as "tse computers," has evolved. These computers utilize entire binary images as their basic computational entity. This is in contrast to conventional computers that utilize a bit as their basic computational entity. Because of their ability to perform thousands of operations simultaneously, they have the potential of operating orders of magnitude faster than conventional computers. They are ideally suited for spacecraft onboard image processing tasks.
    • System Alternatives for the Public Service Satellite Consortium

      Janky, James M.; Potter, James G.; Lusignan, Bruce B.; The Federation of Rocky Mountain States, Inc.; Stanford University- (International Foundation for Telemetering, 1975-10)
      The purpose of the Public Service Satellite Consortium is to foster the shared use of satellites as a distribution mechanism for social services in health and education for public and private non-profit users. The utility of a consortium lies in its ability to aggregate a large number of small, diverse users into a market group which can then share the costs for the space segment and take advantage of the economies of scale in procurement of ground equipment. A summary of the technical analysis of the alternatives for both the space and ground segment equipments is presented, along with cost estimates. The recommended configuration consists of 20-watt transponders and on the ground, eight- to fifteen-foot diameter antennas, using parametric amplifiers. The capital cost for the electronics alone for a Community Antenna is under $9,500 in quantities of 1000 units. This low relative cost makes it possible for many new users to benefit from satellite technology.
    • Detectors Based on Conditional Tests

      Kassam, Saleem A; Thomas, John B.; Princeton University (International Foundation for Telemetering, 1975-10)
      The detection of a known signal in additive noise is an important function in many receivers. Nonparametric detectors, such as the sign detector, will result in systems with a constant false alarm rate, but usually suffer from a lower power compared to optimum parametric detectors. In this paper a conditional statistical test is used to obtain nonparametric detectors more powerful but still almost as simple to implement as the sign detector. The technique of conditional testing is therefore useful in obtaining improved detectors for practical use.
    • Low Data Rates Necessary for RPV Command Guidance

      McIntyre, G. W.; Spencer, B. M.; Sperry Univac (International Foundation for Telemetering, 1975-10)
      In the design of a tactical multi-remotely piloted vehicle (RPV) data link, the RPV data rate and update rate are crucial to the multi-RPV scenario. Data rates on the order of 150 bits per second per RPV or fewer and update rates of fewer than 2 per second per RPV must be used if the RPV's are to operate successfully in a hostile jamming environment. This limit is imposed by the amount of RF spectrum that can be obtained for applying spread-spectrum to protect the data channel. Through data management all necessary RPV command and telemetry functions can be handled at these rates.
    • L-Band, 1.2 m Parabolic Antenna-Noise Temperature Measurement

      Taylor, Ralph E.; Hill, James S.; NASA, Goddard Space Flight Center; RCA Service CO (International Foundation for Telemetering, 1975-10)
      Extensive antenna-noise temperature measurements at 1.6 GHz (L-Band) were made using a 1.2 m (4 ft. diameter) parabolic dish antenna mounted on the Flying Bridge of a modern 15,690-ton, commercial-container ship owned by the United States Lines. Both in-harbor and at-sea radiometer measurements were made that indicated a steady background, antenna-noise temperature value slightly less than 70 degrees kelvin (K) at elevation angles of 5°, and greater, at 1.6 GHz. A comparison of theoretical and measured values indicate excellent agreement within about 5K for at-sea data. These measurements should be especially helpful to RF equipment designers of maritime, L-Band shipboard terminals for operation with the two, geostationary, maritime satellites, Marisat-A and -B.
    • 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.
    • Surface Acoustic Wave Devices for Communications

      Webb, D. C.; Naval Research Laboratory (International Foundation for Telemetering, 1975-10)
      Many surface acoustic wave (SAW) devices are now sufficiently well-developed that they can have a significant impact on systems design. This paper reviews the properties and limitations of SAW devices which seem particularly well suited to communications. The simple bandpass filter is considered in detail as it will undoubtedly see the widest usage of all SAW devices. The application of SAW analog matched filters in phase-shift-keyed synchronization and data demodulation is also discussed. Finally, SAW resonators and oscillators are briefly considered. A number of examples are included which show how system performance can be improved through use of SAW technology.
    • Projection of Timing Capability and Spacecraft Clock Calibration in 1980's

      Chi, Andrew R.; NASA (International Foundation for Telemetering, 1975-10)
    • 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.
    • On The Concatenation of Self-Orthogonal Codes

      Wu, W. W.; COMSAT Labs (International Foundation for Telemetering, 1975-10)
      The concatenation of convolutional self-orthogonal codes with threshold decoding is suggested on the basis of extensive error run length statistical observations at the outputs of the decoders. Simulation results are reported and some discussion is provided.
    • L-Band Maritime Experiments

      Brandel, D. L.; Kaminsky, Y.; NASA GSFC; MITRE Corp (International Foundation for Telemetering, 1975-10)
      The authors have directed the technical portion of the MARAD maritime communications experiments using the NASA ATS-6 satellite. The MARAD experiments were conducted with satellite terminals placed on two commercial ships for evaluation of the communication service similar to that which will be available with the maritime commercial satellite system. These experiments also evaluated the benefits to fleet management through utilization of the communications services. Furthermore, evaluation of position determination using satellites was also made. These experiments were conducted from the MARAD earth station located at Kings Point, N. Y., and the NASA earth station at Rosman, N. C. Three modems having voice and digital data and a stabilized shipboard L-band antenna system were evaluated. Present results indicate that future commercial communications satellite systems will provide the expected high-quality service, particularly when attention is given to improving the reliability of components, such as the vertical reference system used by the shipboard antenna. The results of the experiments conducted indicate that the ship antenna demonstrated successful tracking of the satellites for test period intervals of 4 to 6 hours without the need for operator adjustment. The ship position determination tests show good measurement repeatability, but with significant bias errors which may result from satellite ephemeris. Finally, the data analyzed demonstrated the ability of future commercial satellite systems to achieve a probability of bit error of better than 10-5. Further data analysis is needed to completely confirm these digital data results.
    • Maximum Likelihood Processing of Experimental Retransmitted Four Frequency Omega

      Rupp, Walter E., Jr.; Calise, Clara L.; Dobry, Thomas E.; Department of the Navy (International Foundation for Telemetering, 1975-10)
      The Global Rescue Alarm Net (GRAN) System utilizes the Omega navigation signals and geopsynchronous satellites for a world-wide search and rescue system. A series of tests was conducted by the Naval Air Test Center, Patuxent River, Maryland, during September and October 1974, to demonstrate the position locating potential of four frequency Omega. In these tests four-frequency-Omega data was retransmitted from seven remote sites through Lincoln Experimental Satellite 6 (LES-6) to a ground station in Dallas, Texas, where it was recorded on magnetic tape. This paper will describe the equipment used to receive the Omega signals and retransmit them to the satellite, the satellite linkace and the ground station reception and recording of the phase data. It will also describe the processing of the collected data using a maximum likelihood estimator and the results of the processing. Finally, the paper will present the conclusions and recommendations drawn from these tests for the use of four frequency Omega in a world-wide search and rescue system.