Now showing items 21-40 of 51

    • 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.
    • 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.
    • 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.
    • Data Reduction System for the Modular Auroral Probe

      Eaker, N.; Southwest Center for Advanced Studies (International Foundation for Telemetering, 1969-09)
      A data processing system has been developed to process PCM and analog data received from the Modular Auroral Probe series of rocket payloads. The system has been designed to take advantage of the availability of an IBM 360-50 general purpose digital computer with IBM 1827 and 1828 input/output terminals. Utilizing a general purpose computer which has the above mentioned terminals has resulted in a minimum cost in new equipment required to perform the processing operations.
    • 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.
    • The S-Band Telemetry, Tracking and Command Experiment

      Pickard, R. H.; Schmid, P. E., Jr.; Heffernan, P.; NASA Goddard Space Center (International Foundation for Telemetering, 1969-09)
      The ATS-F S-band Telemetry, Tracking and Command Experiment is designed to develop and demonstrate critical aspects of the technology necessary to an operational tracking and data relay satellite (TDRS) system within the framework of NASA's existing applications flight programs. The experiment involves the implementation and operation of a two-way radio link between a synchronous satellite (ATS-F) and a near-earth orbiting satellite (Nimbus E). The link will be used for precision range and range-rate tracking of Nimbus E from ATS-F, relay of Nimbus E telemetry to the ground via ATS-F, and command of Nimbus E from the ground through ATS-F. The basic purpose of the experiment is to gain experience in the implementation and operation of real time telemetry, tracking, and command links using a synchronous satellite relay. A specific major program goal is to establish the extent to which it is possible to determine the orbit of a near earth orbiting spacecraft using tracking data obtained from a synchronous satellite. It is anticipated that the experiment will be of great value in defining the theoretic and practical problems associated with the design, implementation, and operation of a future TDRS system.
    • Concepts of Integrated Adaptive Data Transmission Systems

      Filipowsky, Richard F.; IBM (International Foundation for Telemetering, 1969-09)
      Telemetry systems require the transmission of information in analog, sampled, and digital forms. There also are requirements for spectrum conservation, for minimum spurious transmission outside the assigned band, and for highest flexibility in multiplexing and in accepting a wide range of sensors. The paper describes the conceptual design of an advanced information transmission system that operates basically in the sampled mode, but that can accept analog inputs through an information compressing sampler or digital inputs by taking one sample of each input bit and making binary decisions in the receiver. The system uses three different encoding processes in an integrated manner. The first encoding process is performed by a redundancy reducing computer-like subsystem called the contractive encoder. Its purpose is to eliminate unnecessary samples while keeping the essential samples at their correct place on the time scale. Repetition of already transmitted samples. or the insertion of samples from other channels will fill the space of samples that have been removed. The second encoding process is performed by a distributive encoder. The purpose of this part of the information processor is the protection of the information against sudden pulsive disturbances. The distributive encoder spreads the information content of each sample over tens to hundreds of other samples in an ordered manner. If, during transmission, one sample or a group of samples is heavily mutilated by pulsive disturbances, the corresponding decoder in the receiver will recover most of the information of these mutilated samples from the other undisturbed samples while spreading the energy of the pulsive disturbances over all samples so that it contributes only a negligibly small error to any one of them. The third encoding process is performed by the modulative encoder. This device has the task of shaping the samples that are produced by the distributive encoder into bandlimited waveforms so that a noise-like, bandlimited composite transmission signal with a uniform spectral distribution is finally fed into the communication channel. Many adaptive features and the option to use a return channel for repetitions of blocks of samples give the system high stability, high efficiency, and low error ratio.
    • 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.
    • Flexible Format Generator Design Techniques

      Rathbone, W. M.; Lockheed Electronics Company (International Foundation for Telemetering, 1969-09)
      A Flexible Format Generator is described for use in a Manned Spacecraft Data Management System. The design uses a memory for storing and controlling a wide variety of sampling formats. Design techniques and their benefits are discussed. Particular emphasis is placed upon functional organization. Techniques are described for combining truncated relative addresses with Mode Codes and Programming Instructions. Software counters are stressed and close attention is given to Power Strobing. These techniques should find application in a wide variety of data management systems.
    • 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.
    • A High Power Versatile Feed System for Communications Satellite Usage

      Hurlburt, Roderic W.; Reiser, Lloyd L.; Yaminy, Roger R.; Radiation Systems, Incorporated (International Foundation for Telemetering, 1969-09)
      The high power versatile feed system for communications satellite usage is of the three-channel monopulse type capable of simultaneous operation over the receiving frequency band of 3700 to 4200 MHz and the transmitting frequency band of 5925 to 6425 MHz. The feed system provides an on-axis transmit beam for the upper frequency range and three-channel monopulse tracking and receiving outputs for the lower frequency range. These simultaneous transmit and receive functions are orthogonally polarized. The feed system consists of a multi-element aperture array with an associated remote polarization control panel. The system is capable of processing transmitted signals of power levels up to 12 kw for the purpose of satellite command and data transmission. It is also capable of processing the relative azimuth and elevation error signals for satellite tracking. The feed system is suitable for primary focal point excitation of parabolic reflectors (F/D between .45 and .6), and for dual reflector or Cassegrainian systems. The sum and difference mode of operation are precisely controlled with a front aperture to provide the proper illumination functions for the particular reflector systems, thus achieving high system efficiencies and correspondingly high G/T ratios.
    • 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.
    • 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.
    • Coding - An Engineering Tool for the Digital Telemetry Link

      Muller, Ronald M.; NASA/Goddard Space Flight Center (International Foundation for Telemetering, 1969-09)
      Various digital coding techniques are discussed from an engineer's and user's point of view. Each technique is displayed in a uniform way which measures performance against the best possible (Shannon) channel. Encoding-decoding complexity and other "system" merits and drawbacks of each technique are discussed. The reader is introduced to coding by drawing analogies with an everyday and familiar coded communication channel - spoken English. Bit, word and block error detection and correction techniques are then presented. Lastly, a concatenated block code scheme which combines these techniques is developed.
    • Recent Developments in Algebraic Decoding

      Chien, R. T.; University of Illinois (International Foundation for Telemetering, 1969-09)
      Recent developments in algebraic coding theory, particularly in the area of decoding techniques, has made the block coding approach much more attractive for practical systems. Advances have been made in decoding algorithms, implementation and software approaches covering such areas as burst correction, random error correction and the correction of multiple bursts. In this paper a review is given on these recent developments from the point of view of applications. These developments shall be discussed with regard to decoding complexity, computational methods, hardware and software considerations, throughput and cost effectiveness tradeoffs.
    • 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.
    • 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.
    • S-Band Phased Array Telemetry Receiver

      Kent, R. C.; Ryan Aeronautical Company (International Foundation for Telemetering, 1969-09)
      A phased array receiver operating at S-band has been developed to automatically track a moving telemetry transmitter by electronic beam steering. Each array module consists of an antenna, mixer, IF amplifier and local oscillator. Beam steering is accomplished by a unique method of controlling the output phase of the local oscillator. The antenna beam may be moved in a continuous scan through 120° in azimuth and elevation. Tracking rates as high as 100° per millisecond are achieved with no moving parts.
    • S-Band Antenna Systems for Missiles

      Hill, John E.; Grander Associates (International Foundation for Telemetering, 1969-09)
      Some thoughts are presented concerning methods of obtaining reliable RF Telemetry links at S-Band, by sharing the effort to obtain such reliability between the airborne and ground station antennas. The form the specifications for airborne antenna system may take is discussed, as are methods of presenting and evaluating performance data. A brief history of the development of the S-Band antenna system for the Athena H Missile is related. In conclusion a variety of antenna types suitable for missiles are presented with a discussion of their virtues and deficiencies.