• NASA Standard 4 x 10⁹ Bit Spacecraft Tape Recorder

      Welch, James P.; Odetics, Inc. (International Foundation for Telemetering, 1977-10)
      The concept of employing standard spaceborne hardware to meet the needs of present and future spaceborne missions is the beginning of a new era. In this paper, attention is focused on describing the functional characteristics of a 4 x 10⁹ bit magnetic tape recorder that will become the standard tape recorder for future satellite missions. The recorder development was directed by NASA Goddard Space Flight Center.
    • NASA Standard Communications and Data Handling Subsystem

      Robinson, Daniel L. (International Foundation for Telemetering, 1977-10)
      At the 1975 International Telemetering Conference Charles F. Trevathan discussed the Multimission Modular Spacecraft (MMS) in general and the Communications and Data Handling (C&DH) subsystem in particular. The National Aeronautics and Space Administration's Goddard Space Flight Center (NASA GSFC) Is managing the MMS program and is integrating the first spacecraft, the Solar Maximum Mission, in-house. Contracts have been let for the Modular Power Subsystem (MPS), Attitude Control Subsystem (ACS) and the Communications and Data Handling (C&DH) Subsystem. The C&DH subsystem provides the command and telemetry link between the spacecraft and the terrestrial system; distributes commands to and collects telemetry from all spacecraft systems via a duplex serial multiplex data bus and Remote Interface Units (RIU's); and contains on board computation capability. The C&DH is a single 4 x 4 x 1- 1/2 foot module. The staffed module weighs 270 pounds including 60 pounds of mission unique equipment. The future for this kind of versatile hardware is exceptionally bright as it is cost effective and its modular structure permits repair, refurbishment and even modification/dating in space.
    • NASA Teleconferencing Pilot Project (An Evaluation of Teleconferencing as a Substitute for Travel)

      Fordyce, Samuel W.; NASA (International Foundation for Telemetering, 1977-10)
      NASA conducted a Pilot Project during 1975 and 1976 to determine the extent that teleconferencing could replace travel to meetings. The network consists of approximately 34 teleconference rooms and 50 fast facsimile machines, all interconnected on private lines to a master switchboard in Huntsville, Alabama. In addition, portable conference telephones augmented the voice network, and experimental video teleconferences were tried. Evaluations show that the teleconferences "saved" travel costs approximating 21% of the travel budget at a communications cost of 3% of this budget. The unused travel funds were diverted into travel other than to management meetings, and consequently, coordination may have improved. This paper discusses the operation of the Pilot Project, which has matured into an operational teleconference network. This experience may be of value to other organizations wishing to adopt teleconferencing.
    • New Types of Flush-Mounted Telemetry Antennas

      Sindoris, Arthur R.; Jones, Howard S., Jr.; Reggia, Frank; Department of Army (International Foundation for Telemetering, 1977-10)
      Over the past few years new and unique types of cavity-backed, slot antennas have been developed that mount flush to the surface of a missile. These antennas have been designed and built to operate in the 300 MHz to 3 GHz frequency range and to produce low-gain (typically isotropic) wide-angle coverage with moderate radiation efficiency. As well as insuring good electrical performance, the basic design employs a copper-clad, dielectric-loaded cavity into which the radiating slot is machined or etched. This construction technique provides four important advantages: (1) The almost arbitrary shape or form factor of the cavity allows flush mounting to the surface of the missile or sandwiching between internal components with only the radiating slot exposed to the exterior of the missile. (2) Fabrication is simple. (3) Cost is low. (4) Mechanical strength is high. The cavity backing the slot is filled with a moderately high, dielectric constant material (such as a silicone, Teflon, or epoxy fiberglass) with a relative permittivity in the 2.5 to 4.5 range to decrease the size of the cavity and to provide mechanical strength to the antenna. The RF connection to the cavity is made by an inductive post and a coaxial connector. A 50 ohm input impedance is obtained over frequency bandwidths of 3 to 10 percent. By connecting two or more of these slot antennas together in a prescribed phase and amplitude relation, the direction of the radiation pattern can be controlled. Sidelooking or forward-looking patterns are possible by simple changes in feed network cable connections. The easy tunability of one of these new types of antennas allows application over greater than a 2:1 frequency range without any change in antenna dimensions.
    • Omnidirectional Telemetry Antennas

      Munson, Robert E.; Ball Brothers Research Corporation (International Foundation for Telemetering, 1977-10)
      Missiles, rockets, and satellites need as much uniform gain as possible to provide continuous telemetry coverage. The theoretical limit of an ideal antenna would be 0 dB gain with 100 percent coverage of 4π steradians. It is not practical to attain the theoretical limit in practice on missiles, rockets, and satellites. This paper describes how closely the theoretical limit can be approached.
    • A Practical Look At Antenna And Propagation Requirements in Biotelemetry Systems For Fresh Water Fish

      Lindsay, J. E.; Long, F. M.; Weeks, R. W.; University of Wyoming (International Foundation for Telemetering, 1977-10)
      Propagation from a transmitter/antenna implanted in a fresh water fish is discussed. The choice of operating frequency based upon fish size, antenna efficiency and refraction effects is presented. The implanted linear antenna is placed laterally along the fish. It is shown that for parallel polarization (E in the plane of incidence) the wave, in air, has polarization dependent upon the elevation angle of the receiving antenna. For perpendicular polarization the polarization of the wave is always horizontal. Hence the polarization of the signal in the air depends upon the fishes position in the water. This leads to the conclusion that ground based receiving antennas should be circularly polarized so that either case can be handled. For air-borne tracking, the major cone of reception places the aircraft at higher elevation angles and hence requires a horizontally polarized antenna. Since the fish can be at various azimuthal angles, a circularly polarized antenna placed beneath the aircraft is dictated. The paper concludes with a discussion of an actual operating system as used by the U.S. Fish and Wildlife Service on the Truckee River.
    • Processing Radiation Data on Board TIROS-N Satellite

      Wisniewski, J. H.; Ford Aerospace & Communications Corp. (International Foundation for Telemetering, 1977-10)
      The function of the data processing unit (DPU) as part of a space environment monitor subsystem is described, with emphasis on special features in the data handling process. Important design goals for achieving DPU performance are outlined. Design implementation to achieve these goals is discussed. Some of the more complex circuits are described in detail as examples of onboard data processing. The packaging approach for effecting savings in weight and power is also presented.
    • Pseudo-Random Code Sidelobe Canceller

      Haber, Conrad H.; Nossen, Edward J.; Government Communications Systems RCA (International Foundation for Telemetering, 1977-10)
      During acquisition of direct sequence pseudo-noise signals, time sidelobes are produced at the correlator output which will degrade detection performance. These sidelobes may be the result of additive noise, channel distortions, deliberate jamming or the non-ideal correlation function of truncated code sequences. In order to minimize these sidelobes, special codes can be selected based on their low sidelobe levels, or some special sidelobe reduction or cancellation algorithm may be devised. A sidelobe cancellation algorithm for use with LSI correlators has been simulated. Segments of a maximum length code word as well as a totally random bit stream were tested. The simulation results show that the largest sidelobes are reduced by a small amount; however, the majority of the sidelobes are reduced by as much as 6 dB. Consequently the false alarm rate for a particular threshold setting may be reduced. A compatible technique for the derivation of a CFAR reference from the same correlator was also successfully simulated.
    • Quadrature Modulation Hybrid Voice and Data Modem

      Lerner, Theodore; Lerner Technology Inc. (International Foundation for Telemetering, 1977-10)
      The Quadrature Modulation Hybrid Modem is a new system designed to provide voice only, data only, or combined voice and data communication. It provides good voice intelligibility at low values of C/N0 by making use of a quadrature modulation technique which permits essentially nonthresholding demodulation of the voice signal. Power sharing between voice and data signals can be easily changed to accommodate different requirements. Intelligibility tests have been performed and indicate an intelligibility of 90% in the voice-only modem at a value of C/N₀ of 43 dB-Hz, and an intelligibility of 80% in the combined voice and data mode at a value of C/N₀ of 43 dB-Hz with an error rate for data of 10⁻⁵.
    • Results of a Q-M/PSK Data Modem Performing in a Hybrid, Voice and Data Mode, Through the ATS-6 Satellite

      Golab, Joseph; Duncombe, Christopher; Bland, Robert G.; U. S. Department of Transportation (International Foundation for Telemetering, 1977-10)
      The Transportation Systems Center (TSC), under the sponsorship of the FAA, has been involved in the development of advanced voice/data multiplexed modems applicable to ground-aircraft communications via satellite in support of the AEROSAT program. TSC was assisted by the Canadian Ministry of Transport (MOT), Communications Research Center (CRC), in the planning and conducting of recent flight test experiments using the NASA ATS-6 satellite.
    • Review of Microstrip Antenna Development at the Pacific Missile Test Center

      Kaloi, C.; Pacific Missile Test Center (International Foundation for Telemetering, 1977-10)
      Pacific Missile Test Center personnel have been conducting theoretical and experimental studies on microstrip antennas since 1965. A number of operational microstrip antenna systems have been developed. This report reviews development efforts at Pacific Missile Test Center on types of microstrip antenna elements used in these operational systems. Results of near field probing of different microstrip antenna elements are presented. These results are used as a basis to discuss microstrip antenna electrical characteristics such as orthogonal current oscillation, orthogonal charge oscillation, dipole moment of charge distribution oscillation, dipole moment of charge distribution rotation, far field radiation patterns, polarization, etc. Application of microstrip arraying techniques on thin flexible substrates that can be readily mounted conformally to the exterior surface of a missile without missile disassembly is discussed.
    • A Satellite Automatic Control System

      Bleiweis, J. J.; Redman, P. C.; COMSAT Laboratories (International Foundation for Telemetering, 1977-10)
      The primary task of existing satellite control centers is to automatically monitor the operational performance of existing satellites and to manually generate control commands so that these satellites remain within specified operational limits. This paper describes some basic characteristics of an existing satellite control center and identifies a method that may be employed to gradually introduce automatic commanding to the facility. Candidate methods of automatic commanding are described.
    • Self-Steering Arrays

      Kummer, W. H.; Hughes Aircraft Company (International Foundation for Telemetering, 1977-10)
      Self-steering arrays using complete receiver-transmitter-signal processing systems to direct the beam of an antenna automatically have been developed. These systems offer an alternative to mechanically gimballed systems for satellite communication applications. The operation of such systems using either a pilot signal or a phased lock loop technique for self-steering is described. Also described is an engineering model built for satellite-to-earth communications which incorporates these techniques. Additionally, other systems now in breadboard configurations are mentioned briefly. A summary of power requirements for a projected 25-module system has been included to indicate the feasibility of larger systems. Test results for the engineering model have proved satisfactory, and show that these systems can definitely be valuable in applications similar to the tracking and data relay satellite system (TDRSS) described here.
    • Sideband Lock SCPDM Modem for Simultaneous Voice and Data Communications

      Harris, Konstantine W.; Udalov, Sergei; Magnavox; Axiomatix (International Foundation for Telemetering, 1977-10)
      A modem technique for simultaneous transmission of voice and digital data is presented. The salient feature of this technique is the use of quadrature carrier multiplexing of a suppressed clock pulse duration modulation (SCPDM) signal with a biphase NRZ data stream. A novel method for separating the voice and data components at the receiver is described. Data bit error rate and voice intelligibility test results are presented and discussed.
    • Some Operational Considerations in Deploying Anti-Jam Communications

      Goldman, Herbert B.; Hughes Aircraft Company (International Foundation for Telemetering, 1977-10)
      Operational and deployment considerations are described to enhance the performance of jam resistant communications. The potential different ground propagation characteristics of spread spectrum and CW type waveforms are used to the advantage of the communication system. Emphasis is placed on the use of tactical relay to continuously optimize against the jammer. Tactics such as spoofing are described as a technique in confusing the intelligent jammer. The objective of this paper is to illustrate how anti-jam communications with nominal AJ performance improvement can effectively be employed in a ground environment. These include the brute force and the so-called intelligent or sophisticated jammer. For many years the utilization of anti-jam communications has been stifled in anticipation or the optimum solution against the optimum jammer. When evaluating a "one on one" scenario where the jammer is dedicated to jamming a specific link there is an unending subset of tradeoffs of optimum techniques to consider. However, when the jammer is trying to disrupt communications along a broad geographical axes. the techniques of jamming and communicating should be based on more general operating conditions. The ground communications environment in the presence of ground-based jamming presents the greatest opportunity for improving performance as a function of propagation anomalies and the use of relay. Airborne terminals within line of sight of the jammer have the most severe jamming environment. Ground based terminals generally will have an advantage of terrain against the ground based jammer. Those links that exhibit poor communications margin should always have the option of an alternate route in a jamming environment. The alternative to an alternate route is to provide excessive performance margins for worst case analysis. Unfortunately there is a significant cost factor associated with this latter approach. An important element of the scenario is the concept of position location. The use of position location and reporting equipment enables the apriori determination of appropriate links by different classes of users. As an example an aircraft can maneuver close to a ground terminal for communications to utilize the advantage of range ratio. This can be done in the worst case of a close Air Support Mission where the FO must provide voice or digital data to direct a strike at several mobile targets. At high altitudes the AC may be jammed but at low altitude the link may be viable. At low altitudes the aircraft A-G link will be constrained to a small geographic area and must therefore know which area to cover. The use of GPS can also be enhanced at low altitudes against the ground based jammer if acquisition of the GPS signal can be speeded up. The use of a digital matched filter (DMF) for CA code acquisition can provide this capability.
    • Telecommunication Applications for CTD Devices

      Gopen, C. W.; Reticon Corporation (International Foundation for Telemetering, 1977-10)
      A relatively new type of component, the CTD (Charge Transfer Device) is now available to the commercial market. After five years in the development lab, these parts are finding their way into many applications including telecommunications. This paper will give a brief overview of the device theory and discuss three particular devices: 1) a transversal filter, 2) a Binary Analog Correlator, and 3) chirped transversal filter used to implement a Discrete Fourier Transform.
    • Telemetry Antennas for Deep Space Probes

      Brejcha, Albert G.; Smith, Charles A.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1977-10)
      The requirement for real time imaging telemetry and the continued increase in science payloads on deep space missions have played a major role in the evolution of deep space probe telemetry antennas. This paper describes the high data rate telemetry antennas that were flown on the Mariner Mars 1969 and 1971, the Mariner Venus Mercury 1973, the Viking 1975 and the Voyager spacecrafts. Performance parameters are reviewed and general design concepts are described. The Mariner Mars 1969 and 1971 antennas were single frequency (S-band), one meter diameter antennas. The Mariner Venus Mercury 1973, Viking 1975 and Voyager antennas were dual frequency (S and X-band), with diameters of 1.4 meters, 1.5 meters and 3.7 meters respectively.
    • A Test System for a Miniature Neutron Detector

      Balls, Jerry D.; Bowers, John L.; The Bendix Corporation (International Foundation for Telemetering, 1977-10)
      A flexible automated test system for calibrating and testing a miniature neutron detector, used in telemetry systems, is described. The test system is cost effective, easily calibrated and maintained, and was available for use 6 months after design initiation.
    • Tethered Balloon for Checkout of Computer-Controlled Antennas

      Baggot, H. E.; Wynn, J. B.; Interstate Electronics Corporation; Department of the Navy (International Foundation for Telemetering, 1977-10)
      During operational tests of the U.S. Navy's Poseidon missile, an instrumented ship tracks every test missile launched by the nuclear subs. The key sensor aboard this launch-area support ship, the USNS RANGE SENTINEL, is its antenna system. Onboard computers switch the ship's four independent, main S-band antennas (Fig. 1) to capture up to four missiles fired in succession and to expedite command action (e.g., continued flight or destruct). This multi-antenna control by computer leads to a complex testing problem for the computer software, constrained by the need for cost effectively proving the software's operational capability without penalizing hardware development. Rigid control of hardware-caused variables, and a near-operational test environment, are vital Software test prerequisites. To this end, using a stable RF pointing source at altitude above the antennas (i.e., to reduce parallax distortion and multipath effects) is a preferred approach in testing antenna-management software. This paper describes two experiments* to (1) initially establish the feasibility of using an airborne S-band telemetry transmitter as an RF signal source for checking out the USNS RANGE SENTINEL's antenna control, and then (2) demonstrate the effectiveness of this RF source in verifying the ship's antenna alignment and validating the operational antenna software.
    • Understanding & Specifying Hi-Density Digital Recording Systems

      Schulze, Glen H.; Bell & Howell (International Foundation for Telemetering, 1977-10)
      Rapid advancement of hi-density digital recording technology has left most user organizations in a confused and bewildered state with respect to understanding and, more importantly, specifying hi-density recording systems. Users attempting to acquire advanced hi-density hardware either without procurement specifications or with incomplete or shallow specifications will probably gain the needed experience too late, after an unusable system has been delivered. Several prominent user facilities have recently bought and accepted hi-density recording hardware and immediately been forced to retire the equipment from use to avoid disastrous embarrassment. Other users have had to redesign accepted equipment before it could be used. One user who blindly accepted a proposal to convert several newly ordered analog recorders to a digital format had to remove and dispose of the digital electronics after delivery and revert back to analog methods. The ability to professionally specify and technically monitor a hi-density recording system contract can only be based upon a thorough understanding of the high density digital coding, recording, reproducing and decoding process. The purpose of this paper is to identify and discuss the more important elements of this emerging technology for users who suddenly find themselves needing this capability.