• DIGITIZING SATELLITE GROUND STATION TT&C SUBSYSTEMS

      Chen, Thomas J.; Ford Aerospace & Communications Corporation (International Foundation for Telemetering, 1983-10)
      There are many advantages to implementing satellite ground station TT&C functions using digital LSI and VLSI technology: increased reliability, reduced size, weight and power and enhanced performance. The functions of a satellite ground control station that could be digitized in the future are identified. The evolving capabilities in digital chip technology are reviewed to indicate how they would be applied to satisfy these TT&C functions. Fundamental performance limitations of these technologies are also identified.
    • SYSTEM TRANSMISSION PARAMETERS DESIGN FOR THRESHOLD PERFORMANCE

      Rosen, Charles; Microcom Corporation (International Foundation for Telemetering, 1983-10)
      The paper is an extension of two previous works published in the ITC 1974 and 1976 proceedings by the same author. It is the intent of this publication to summarize the two previous papers; to include corrections; to expand the explanations; and to add new material. This information has been accumulated from many system designs based on the described procedures. It deals with a variety of transmission systems and combinations of multiplexing schemes. A number of tables and constants are provided as standards to be used in telemetry system design thereby reducing calculating time. System engineers are given a basic step by step procedure and format for the design of any type of transmissions system. Also a computer program is now available to automatically calculate all of the parameters necessary for the system design. The last presentation of the system design procedure dealt with the information accumulated over several years, and established the parameters from which the design equations for PCM and PAM were updated. Since that time a concentrated effort was initiated to verify the correct bandwidth equation which would be optimum for FM/FM Multi-tone Systems. Again cognizant scientists and engineers were contacted and interviewed. From past history and successes, it was well known that the bandwidth equation known as “Carson’s Rule” provided an adequate bandwidth to guarantee the system accuracies. However, it was also known that systems were in use, operating with smaller bandwidth than specified by Carson’s Rule, and also providing acceptable data accuracies. From the best information available, these systems were designed empirically with painstaking testing effort to insure their accuracy. The investigation lead to another bandwidth equation which appears to be the correct approach for providing the optimum bandwidth for Multi-Tone Systems. There is no doubt that this is not the first application of this bandwidth equation, but this author could not find any documented information as to its use or validity when applied to multi-tone systems. This presentation has designated the new bandwidth equation as the “Multi-Tone Bandwith Equation” or “M/T Bc”. The actual equation and its verification are provided later in this presentation. A second corrective update was made in the design of the PAM/FM/FM Channel where the subcarrier design equations are established based on the same parameters as PCM. Since PCM and PAM are both pulse modulation, their design theories are similar for a subcarrier channel. In the final PAM/FM/FM analysis, a lower frequency SCO will be used as compared to that which was previously specified. Again, the validity and verification of this update in the procedure is described later. Finally, a third and significant addition to this presentation has been provided by Mr. Matthew Egler, of Microcom Corporation, who has written four (4) computer programs based on this procedure. Not only does this program provide the system design effort, but also provides a program for the mixing networks required for systems with PCM or PAM baseband, modulation together with a higher frequency SCO Multiplex system on the same baseband PCM/PAM/FM + FM/FM. Without this network, the baseband pulse adulation is rendered useless when coupled with an SCO Multiplex system. A third program available on the same floppy disc, is the computation of the SCO Voltages and mixer amplifier gain necessary for modulating a transmitter with a specified modulation sensitivity in accordance with the channel deviations as computed by the System Design program. The final program is the margin calculation based on the equations and procedure specified in Attachment E of this presentation. Hopefully this presentation will represent the final procedures and equations. However, if any new information is accumulated based on analysis, experimentation, or field use, which has an impact on the result of this paper, a further update will be submitted to keep the methods described herein current and state-of-the-art. It is the author’s contention that the capability to accurate system design lies in the use of the noise equations, and the procedures developed around those equations.
    • DIGITAL HILBERT TRANSFORMER FOR SINGLE-SIDEBAND GENERATION

      Udalov, Sergei; Axiomatix (International Foundation for Telemetering, 1983-10)
      This paper describes a digital real-time implementation of a Hilbert transformer for the generation of single-sideband signals (SSB’s). Design criteria for the transformer are presented and the experimental results are discussed for a typical voice-band channel having a nominal bandwidth of 300 to 3500 Hz. Techniques for generating two independent sidebands (ISB’s) on a single carrier are also described.
    • GALILEO PROBE RELAY RECEIVER: ACQUISITION AND TRACKING

      von der Embse, U. A.; Hughes Aircraft Co. (International Foundation for Telemetering, 1983-10)
      The probe-to-orbiter data link for the Jovian mission uses a Manchester encoded BPSK waveform which is demodulated by the Galileo probe relay receiver. Signal acquisition and tracking consists of a sequential probability ratio signal search, frequency acquisition with a least-squares estimator, wide-band phase lock acquisition, and a self-regulating mode control. A discrete Fourier transform serves as the basic mechanism to generate the algorithms that provide this orderly transition to phase tracking. Acquisition and tracking is addressed in this paper with emphasis on key algorithms, rationale, and theorectical/ measured performance.
    • BIT SYNCHRONIZATION IN THE PRESENCE OF ASYMMETRIC CHANNEL NOISE

      Tsang, Chit-Sang; Lindsey, W. C.; LinCom Corporation; University of Southern California (International Foundation for Telemetering, 1983-10)
      Bit synchronization in the presence of asymmetric channel noise has not appeared in the open literature. It is the purpose of this paper to study the performance of a popular digital clock synchronizer, the Digital Data Transition Tracking Loop (DTTL), in the presence of asymmetric noise. A comparison of the DTTL and Cross Spectrum Synchronization Loop (CSSL) is also provided for special parameter values of greatest interest. Numerical results are presented for design of bit synchronizer in this environment.
    • LOW-POWER FAULT-TOLERANT MICROPROCESSOR-BASED DISTRIBUTED ARCHITECTURE FOR ON-BOARD SIGNAL PROCESSING

      Haas, W. H.; Liao, H. H.; Schoknecht, W. E.; Rockwell International (International Foundation for Telemetering, 1983-10)
      Numerous future space-based systems are being conceived that will require the on-board processing of a volume of data many orders of magnitude greater than the current state-ofthe- art. Such systems must in addition be extremely low power and autonomously fault recoverable. This paper describes a microprocessor-based distributed architecture that has been evolving as a solution to this problem. This proposed architecture features three subarchitectures: synchronous pipeline, dedicated-channel microprocessor array, and multiplebus oriented microcomputer array; as well as internal data compression, distributed control and self testing, and a building block approach to system implementation. Emphasized is the roll of microprocessors in this architecture and the challenge of reducing the overhead required by fault-tolerant processing.
    • MICROPROCESSORS IN DISTRIBUTED BROADCAST RADIO SYSTEMS

      Ostroy, Lester; Holbrow, Willmore F., Jr.; Martinez, Louis (International Foundation for Telemetering, 1983-10)
      Microprocessors are incorporated in several hardware features of a patented new system which uses the wasted power inherent in standard AM Broadcast Radio transmission. This unique system can be used for many applications. The first large-scale demonstration of the capabilities of the system was conducted for the purpose of electrical demand limiting by utility companies. In these trials, control signals were sent to several hundred receivers to shut-down equipment during times of peak load on the utility grid. The receivers for this system were low-cost and microprocessor operated. They were placed over a wide area, up to 175 km from the transmitter, which in these trials was a high-power (50kW), standard AM broadcast station. Control signals did not interfere with the quality nor the reception range of the broadcast station’s audio signal. Data reception by the system receivers had error rates under 1%.
    • MICROPROCESSOR BASED ANTENNA CONTROL UNIT MEETS A WIDE VARIETY OF APPLICATIONS

      DeBrunner, K. E.; Electro Magnetic Processes, Inc. (International Foundation for Telemetering, 1983-10)
      A very powerful and flexible antenna control unit is described. This control unit is built around a Z-80A microprocessor, the STD Bus, and optional math processor. It is designed to work with many existing antenna/pedestals. The unit features modular construction, low profile, intelligent controls, programmability, self-test and self-calibration. The controller is easily customized to specific requirements and user preferences for displays, switch legend and location, and is easily extensible with standard extension panels for additional controls and displays or with custom extension hardware. The controller can be remotely controlled via the IEEE-488 Bus or a variety of serial data link configurations.
    • REVIEW OF TWT DEVELOPMENTS ABOVE 18 GHz

      Weekley, J. Martin; Hughes Aircraft Company Electron Dynamics Division (International Foundation for Telemetering, 1983-10)
      Hughes Aircraft Company - Electron Dynamics Division experience in providing 20 and 30 GHz TWTs for space application is summarized. Development programs for 25 and 50 Watt TWTs at 20 GHz are reviewed. A brief overview of development efforts at 40 to 44 GHz is presented.
    • TECHNOLOGY CONSIDERATIONS IN EHF SATCOM SYSTEMS

      FORD AEROSPACE AND COMMUNICATIONS CORPORATION (International Foundation for Telemetering, 1983-10)
      Millimeter wave systems have had a 20 year development period starting with the pursuit of radio astronomy in the 1950’s to the mm-wave satcoms of the 1980’s. This paper traces the developments of both mm-wave technology and satcom systems to both the present NASA ACTS system and the developing military mm-wave satcoms.
    • LOW NOISE AMPLIFIERS ABOVE 18 GHz*

      Kennan, Wayne; Chye, Patrick; Avantek, Inc. (International Foundation for Telemetering, 1983-10)
      This paper describes the development of low noise GaAs FET amplifiers for 20-22 GHz. These amplifiers achieve a 3 dB noise figure and 19 dB gain with two hybrid stages. In addition, data will be presented on state-of-the-art GaAs FET noise performance above 18 GHz.
    • U.S. ARMY YUMA PROVING GROUND TELEMETRY SUPPORT CAPABILITIES WITH APPLICATIONS TO GPS TESTING

      Bottone, Anthony G.; Electronic Section, STEYP-MDP-E U.S. Army Yuma Proving Ground (International Foundation for Telemetering, 1983-10)
      This paper presents an overview of U.S. Army Yuma Proving Ground Telemetry acquisition facilities as they relate to developmental tests of the GPS system. These systems utilize the latest state-of-the-art in telemetry tracking systems, receivers, and employ a unique scheme for frequency and space diversity combination and signal selection. The telemetry systems presently used can accomodate two simultaneous aircraft in various parts of the range. Through acquisition of telemetry and subsequent reduction, actual realtime differences in X, Y, Z location between three station laser derived position solution and GPS satellite solution can be displayed and recorded. In addition, a summary of latest facility expansion involved in the enhanced support of the GPS testing at the 1600 square mile U.S. Army Yuma Proving Ground will be presented.
    • A PHYSICALLY SMALL DUAL CIRCULAR MICROSTRIP ANTENNA

      DeVries, James M.; Pacific Missile Test Center (International Foundation for Telemetering, 1983-10)
      The microstrip antenna has recently gained popularity because it offers the advantage of flush mounting, small size, and low cost when fabricated by etched circuit techniques. In an effort to further reduce the aperture requirements, two circular microstrip antennas were placed one on the other and fed independently. Utilization of the field null at the center of the circular disk antenna allows independent excitation. In this configuration, two different frequencies can be transmitted simultaneously while sharing the same physical aperture. Polarization of the antennas is linear with well behaved radiation patterns exhibiting gains of 6 dBi. Moderate power levels can be accommodated by selection of suitable substrates and control of dielectric thickness. As a result of the reduced size, the antenna can now be placed in areas otherwise thought impractical. Placement in front of certain antennas or retrodirective reflectors has a very minor effect on their performance.
    • HIGH RESOLUTION DIGITAL DATA TRANSITION ANALYSIS AND TESTING

      Petit, Richard D.; Kode Inc., a Subsidiary of Odetics Inc. (International Foundation for Telemetering, 1983-10)
      The need for margin analysis in high density digital data storage systems is established. A review of margin analysis techniques is presented. This review includes a discussion of time interval analysis and a series of instruments which have evolved as a means of performing this analysis. Emphasis is given to a high resolution (1 nanosecond) statistically oriented embodiment of such an instrument.
    • USE OF FORWARD ERROR CORRECTION IN A GROUND-TO-AIR-TO-GROUND TELEMETRY AND CONTROL LINKS

      Gardner, S.; Levy, E. (International Foundation for Telemetering, 1983-10)
      A forward error correcting (FEC) codec/interleaving system has been developed to improve the signal to noise ratio of a full duplex channel composed of a low rate command and control uplink and a high rate telemetry downlink. The system includes two MIL spec airborne 20 square inch cards and a ruggedized modified LINKABIT standard LV7017HS Convolutional Encoder Viterbi Decoder Ground Unit. The coding parameters used are code rate 1/2, constraint length K=7, 8 levels of soft decision and data rates of up to 20 Kbps for the command link and up to 10 Mbps in the telemetry downlink. Since Viterbi Decoders work best on memoryless Gaussian Noise channels, interleaving is used to randomize the effects of fading, jamming or other bursty types of noise making them appear like white Guassian additive noise to the decoder. A coherent binary PSK modem will ideally provide 10^-5 bit error rate (BER) with Eb/No = 9.6 dB (bit energy per noise ratio). The use of the FEC codecs in the sort decision mode achieves the same BER with 5 dB lower Eb/No, meaning either an increase of the communication range with the same RF equipment or substantial decrease of RF power or antenna size for the same communication range. The same system could be used in a hard decision mode and still provide a gain of more than 3 dB at BER of 10^-5. The coding gain increases as the required BER decreases. The described system could be easily adapted to any command and control link or telemetry link at the above mentioned data rates.
    • LOW COST, LIGHTWEIGHT, SINGLE AXIS TRACKING SYSTEM FOR UNMANNED VEHICLE APPLICATION

      Sullivan, Arthur; Turner, William C.; Electro Magnetic Processes, Inc. (International Foundation for Telemetering, 1983-10)
      Recent events in the Falkland Islands, and in Israel/Lebanon, have made the tactical use of unmanned airborne vehicle systems a practical reality The control of the unmanned vehicles requires a radio uplink, a downlink for vehicle position determination, for telemetering monitored events and functions, and, in some instances, transmission of television or other information. While for some situations the ground antenna can be fixed, the majority of today’s applications require a steerable antenna. This is dictated by the fact that a high gain (and therefore, narrow beam) antenna is required for maximum range, and that for most scenarios, vehicle position must be determined. The increasing use of unmanned vehicles indicates the need for a low-cost tracking antenna system. Use of the tracking antenna in transportable and/or mobile systems calls for a lightweight system. A two-axis antenna, in addition to being heavy, is more than twice the cost of a single-axis tracking antenna system. Slant range of the vehicle is determined by the use of a ranging tone and ground range is determined by comparing altitude data telemetered back from an on-board altimeter with slant range. Complete positional data are obtained given the ground range and the bearing angle from the singleaxis tracking antenna. A microprocessor-based antenna control unit allows all systematic errors of the antenna system to be calibrated out of the angle data. A binomially fed, linearly polarized, folded pillbox horn antenna, having extremely low sidelobes, permits wide angle acquisition, and high elevation angle tracking without introducing bearing angle error. The use of graphite fiber materials for antenna and rotator construction provides savings both in cost and weight. A newly developed lightweight and low-cost single-axis tracking antenna that utilizes all these techniques is described in this paper.
    • PRELIMINARY TEST RESULTS OF THE ELECTRONIC SWITCHING SPHERICAL ARRAY ANTENNA

      Kudrna, Ken; Ball Aerospace Systems Division (International Foundation for Telemetering, 1983-10)
      An Electronic Switching Spherical Array (ESSA) Antenna has been developed for low obiting spacecraft requiring medium gain (+13 dBic) transmit and receive relay capability through the Tracking and Data Relay Satellite Systems (TDRSS). This 145 radiating element antenna is steered with a microprocessor controller by selecting arrays of 12 elements at a time. Approximately 1800 beams can be selected for near hemispherical coverage. The primary method for evaluating this antenna is a composite Radiation Distribution Plot (RDP).
    • AUTOMATING SATELLITE COMMAND AND CONTROL

      Golden, Constance J.; Ford Aerospace & Communications Corporation (International Foundation for Telemetering, 1983-10)
      Existing spacecraft/satellite control requires access to a group of “experts” familiar with each satellite subsystem to be able to analyze and correct spacecraft malfunctions. When remote, mobile satellite control systems are deployed, these “experts” will not be available. Automation of many of the functions currently being performed by these experts and the operators at the consoles will allow these mobile systems to operate autonomously while correcting for anomalies that can be logically identified. This automation can be achieved by implementing artificial intelligence (AI) processes/techniques to the fault detection, command correction process. Techniques from the artificial intelligence development process and algorithms from statistical forecasting methods will be analyzed and tested for applicability in providing automated spacecraft health and status information for one DOD program. Key issues in applying these processes to all critical DOD programs will be identified and discussed.
    • THE NASA DATA SYSTEMS STANDARDIZATION PROGRAM RADIO FREQUENCY AND MODULATION

      Martin, Warren L.; CALIFORNIA INSTITUTE OF TECHNOLOGY JET PROPULSION LABORATORY (International Foundation for Telemetering, 1983-10)
      As space missions have become more expensive, the search for methods to improve efficiency has intensified. One approach offering great potential focuses upon multimission designs in order to avoid early obsolescence. Data handling systems are attractive candidates for the multimission concept because of the high cost of redesign and because the process should be amenable to a high degree of uniformity. By cooperating in the specification of their data systems, NASA and ESA should achieve significant uniformity. Apart from improving the design, this unified approach will facilitate the cross support of one agency’s spacecraft by the other agency’s tracking network. Here, we are concerned with the radio frequency subsystem which links spacecraft instruments with ground-based users. In large measure, the telecommunications system’s characteristics are determined by the ground station’s design. For the concept of cross support to succeed, there must be a substantial similarity between these NASA and ESA designs. Both NASA and ESA have large capital investments in their ground networks. While it might be theoretically satisfying to speak of a single ground system configuration for both agencies, the high cost of the required revisions renders this approach practically unachievable. This paper describes a process for maximizing the commonality of the two agencies’ radio frequency and modulation systems that is consistent with budgetary and scheduling constraints. The two-part program consists of identifying present system similarities and developing a plan for eliminating substantive differences where they are found to exist.
    • THE NEW STANDARD SPACECRAFT TIMECODE

      Connell, Edward B.; Goddard Space Flight Center (International Foundation for Telemetering, 1983-10)
      In an effort to reduce the costs of conducting space missions, the National Aeronautics and Space Administration (NASA) is working to develop data systems standards that are appropriate for application at key interfaces within mission data systems. Use of proper standards can improve multimission support by reducing the need for developing new interfaces and data transforms for each new mission. “Time” is an important parameter for space-acquired measurements because instrument analysis can often be based on a sampled sensor time series and because time provides the most efficient (and often the only possible) linkage between instrument data and externally generated ancillary parameters. Therefore, one of the major aims of the NASA effort has been focused on the development of a standard timecode structure. This paper describes the rationale and form for that structure and provides a proposed definition for an important class of timecodes, the binary unsegmented codes. The structure provides a mechanism for the self-documentation of timecodes, so that any user of the data can interpret time measurements in an unambiguous manner. The binary unsegmented codes are modular and easily machine-readable, and feature expandable resolution and ambiguity periods.