• Active Retrodirective Array for Microwave Power Transmission

      Chernoff, Ralph C.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1979-11)
      An active retrodirective array (ARA) is a phased antenna array in which retrodirectivity of the transmitted beam is produced by electronically conjugating the phase of the pilot signal received by each element of the ARA. ARA's can be easily modified to function as receiving, as well as transmitting, arrays. Due to their inherent failsafe characteristics, ARA's are particularly attractive for microwave power transmission from solar power satellites. Communication satellites and deep space probes are other possible applications. The "Central phasing" principle, in itself a simple generalization of the phase conjugation principle, avoids the need for structural rigidity implicit in conventional phase reference distribution systems. We describe a phase reference "tree" for implementing central phasing in very large ARA's, as well as a new kind of "exact" frequency translating phase conjugator which provides both input-output isolation and freedom from squint. The effects of doppler, aberration, impedance mismatches and multipath are discussed. We report on the performance of an experimental two element ARA, and on the design of an eight element ARA now being built at JPL.
    • Appendix: Eighteenth Annual Report of the Telemetering Standards Coordination Committee

      Pizzuti, Michael (International Foundation for Telemetering, 1979-11)
    • The Application of Frequency Offset Advantage (FOA) in Frequency Coordination

      Raghavan, Srini; Armes, Jerry; Spectrum Analysis & Frequency Engineering (International Foundation for Telemetering, 1979-11)
      A major telecommunications growth area at this time is narrowband digital transmissions via satellites. With the availability of low cost 5 and 10 meter earth stations, and readily available digital ground equipment, this trend can be expected to continue for some time. With the degree of frequency congestion which exists currently in the 6 GHz band, the frequency coordination of these earth stations will become more and more difficult. Since the data rate is generally 56 KBPS or 1.544 MBPS, the satellite uplink carrier frequency is often selected to give a degree of isolation from standard frequency plans used by the terrestrial common carriers. The amount of offset advantage in db to be conceded from a given frequency separation between satellite and terrestrial carriers is a matter of controversy however. This paper describes a computer program written to provide the necessary calculations, the underlying models, and results in the form of parametric curves which can be used directly to obtain the offset advantage for a given carrier separation.
    • The Command and Data Management System of Spacelab

      Bolton, Gordon R.; European Space Agency (ESA) ESTEC (International Foundation for Telemetering, 1979-11)
      This paper describes the Spacelab command and data management system and its support capabilities for various types of experiments in terms of data processing, display, recording, and multiplexing.
    • A Compatible STS/PAM D/RCA SATCOM Telemetry and Command System

      Hoedemaker, R.; Staloff, C.; RCA Astro-Electronics (International Foundation for Telemetering, 1979-11)
      This paper presents a solution to the problem of providing the electrical interface with the NASA Shuttle and PAM D for an RCA Satcom Communications Satellite. The paper addresses the transition to the NASA Shuttle from the present era of expendable launch vehicles as it applies to the command and telemetry electrical interfaces. Final preparation of the spacecraft for launch into the transfer orbit rests with the Orbiter crew rather than the spacecraft contractor launch team. The added dimension of crew safety and the importance of simplifying the preparation task led the requirement for Electrical Airborne Support Equipment (EASE). The conceptual design of this microcomputer-based equipment is described. The EASE monitors the health of the spacecraft and takes adaptive action where appropriate. It also sends prestored command lists to the spacecraft in response to crew-initiated keyboard command functions.
    • Control Aspects of Multibeam or Multielement Spacecraft Antennas

      Foldes, Peter; General Electric Company, Space Division (International Foundation for Telemetering, 1979-11)
      With the rapid development of spacecraft systems the trend is toward more sophisticated and larger on-board antennas. Many of these antennas employ an array of radiating elements, either as part of a feed system illuminating a larger aperture optics or as the direct radiators. The main purpose of using multiple radiators instead of a radiator in conjunction with a large aperture is to introduce a much larger degree of freedom in achieving desirable antenna characteristics. If an antenna system contains n independent radiating elements then the amplitude and phase of each of these elements can be selected for desirable results.
    • Control of Large Communication Satellites

      Gran, Richard; Proise, Michael; Zislin, Alex; Grumman Aerospace Corporation (International Foundation for Telemetering, 1979-11)
      Control of large communication satellites becomes most difficult when the structure gets large enough that the structural motion severely impacts the ability to stabilize the RF antennas. This structural/control interaction means that the control engineer can no longer use "benign neglect" of the structural vibrations, but must design a control that has a bandwidth that exceeds the lowest structural vibratory frequency. This in itself is not a problem as long as the sensors and actuators are colocated. Eventually, the antennas have to be controlled independently and the assumption of colocated sensors and actuators is no longer reasonable. This begins the problem. In this paper, the various approaches that have been proposed for controlling large flexible spacecraft when the structural frequencies and the control frequencies overlap will be described. A new approach to the design of such systems will be described, and a reasonably complex example of a large satellite control will be described. The presentation will show a movie that was produced to illustrate the control of this structure and the consequence of using the approach described in the paper.
    • Convolutional Error Detection on an Additive White Gaussian Noise Channel

      King, Maurice A., Jr.; The Aerospace Corporation (International Foundation for Telemetering, 1979-11)
      Concatenated coding schemes involving a convolutional inner code and a block outer code have occasionally been used in communication systems that are very intolerant of errors. In these schemes the vast majority of channel errors are corrected by the convolutional decoder while the block outer code is used to detect convolutional decoder errors. Block code words containing detected errors are erased. Soft decision Viterbi convolutional decoders operate by comparing path metrics and selecting the path with the largest metric (the maximum likelihood path). There is a substantial amount of information in the path metrics that is not used in this pick-thelargest decision. It is proposed that some of this information be used in a probabilistic decoding error detection scheme. Such a detection scheme would obviate the use of the block outer code. The result is a bandwidth savings at the cost of some additional processing of the convolutional code metrics.
    • Correlation of Tape Dropouts with Data Quality

      Schoeck, Kenneth O.; Kobylecky, George M.; Vandenberg Air Force Base (International Foundation for Telemetering, 1979-11)
      When recording and reproducing telemetry data, signal dropouts are a prime concern to most tape users. The effect of particular depths and lengths of dropouts on data quality must be known before the acceptability of a tape for a specific application can be determined. This paper discusses the correlation of tape dropouts with data quality when recording predetection and post-detection telemetry data and IRIG timing on wideband instrumentation tape, as well as methods of reducing dropouts.
    • Data Pattern Sensitivity in Tracking Performance of an AC Coupled Costas Loop with Hard-Limited In-Phase Channel

      Park, Young H.; California Institute of Technology (International Foundation for Telemetering, 1979-11)
      This paper is concerned with data pattern sensitivity in carrier tracking performance of an AC coupled Costas loop with a suppressed BPSK signal. The signal amplitude suppression factor is derived as a function of data "asymmetry ratio" - the ratio of "1"s to the total number of bits in a period of a periodic signal. For an asymmetric pattern, the effect of AC coupling is noticeable whereas there is almost no effect for symmetric squave wave. The tracking performance with an asymmetric pattern is worse than that with a symmetric pattern. However, it is also shown that as expected, the tracking performance of a DC coupled loop with an asymmetric pattern is better than that with a symmetric pattern.
    • Decentralized Control for Large Communication Satellites by Model Error Sensitivity Suppression

      Sesak, John R.; Bowman, Robert M.; General Dynamics Convair Division (International Foundation for Telemetering, 1979-11)
      The rapid growth in world demand for satellite telecommunications and the limited number of positions in the geostationary arc are leading inexorably to larger, higher capacity communications satellites. This trend, coupled with the projected weight and volume capability of the Space Transportation System (STS), will lead to satellites in the 80s weighing 5000 kg and measuring 50 to 100 feet across. By the end of the century these figures could increase again by an order of magnitude. Such large, low-density structures tend to have closely spaced, low-frequency dynamic modes. At the same time, multibeam-frequency reuse antennas (MBFRA) projecting narrow-spotbearns require pointing stability within a hundredth of a degree or so. The combination of low structural natural frequency and more stringent pointing requirements imposes the need for an entirely fresh approach to dynamic control of communications satellites. This paper outlines such an approach. A modern optimal control methodology is advanced that provides decentralized modular control for large communication satellites. The fundamental property of the control algorithm is its ability to stabilize certain subsets of vibration modes without disturbing others. This decoupling action allows the control task to be implemented in a modular or building block fashion so that different modal subsets are stabilized by separate controllers. Decentralization according to functional task is also possible such that noninteracting rigid body and elastic body control is achieved. Thus, the technique provides a solution for the problem of rigid body control in the presence of low frequency elastic modes that are in the rigid body controller bandwidth. The design methodology, termed Model Error Sensitivity Suppression (MESS), is a derivative of modern optimal control and estimation theory. Several examples illustrate the capability of the design algorithm.
    • The Design of CO₂ Laser Communication Systems

      Einhorn, Arthur J.; Hughes Aircraft Company (International Foundation for Telemetering, 1979-11)
      Future demands for more information transfer in space will increase the demand for wider space communications with narrower beamwidths. Both of these requirements suggest using as high a carrier frequency as possible. The wider bandwidth is necessary to increase the information carrying capacity. The narrower beam allows the use of a smaller amount of transmitter power to a distant receiver and concomittenly results in larger antenna gains. The Carbon dioxide (CO₂) laser system meets many requirements for a space qualifiable space communication such as wideband modulation capability, potentially long life and reliability. In this paper we discuss several aspects of the design of a CO₂ laser communication system for space application in terms of overall functional requirements, system tradeoffs and subsystem component selection. The results require use of state-of-the-art components which are or can be space qualified.
    • Development of a Seven Channel Telemetry Transmitter

      Seeley, R. L.; Long, F. M.; Pauley, J. D.; Weeks, R. W.; Naval Ocean Systems Center; University of Wyoming; University of Colorado Medical Center (International Foundation for Telemetering, 1979-11)
      Study of electroencephalograms (EEG) under normal behavior conditions required the development of a small, reliable telemetry system. Here two hybrid ceramic packages were attached face to face to provide a hermetically sealed seven channel telemetry transmitter with glass to metal seals around the seven differential pairs of input leads and the power supply leads. The transmitter's antenna is enclosed in the package by using two loops of gold substrate etched in a pattern around the other circuitry. The package measures .8 x 2.2 x 2.4 cm and weighs 8.5 gms. Input noise level is below 1 microvolt (rms) and dynamic range is from 1 to 250 microvolts (rms) with a frequency response (6 dB down) of 1 Hz to 150 Hz. Power requirements are 2.1 to 3.6 ma at 2.0 and 3.3 vdc., respectively, with at least 80% (3.3 and 9.5 mw, respectively) going to the radio frequency stage. Data are time multiplexed for pulse position modulation of an 88 to 108 MHz carrier. Maximum measured range of transmission with a 3 volt battery has been 10 m in air. This transmitter is well suited for the study of any animal large enough to carry the package and a battery. Other biopotentials such as EMG and ECG can be telemetered by increasing multiplexor rates and/or attenuating input signal levels.
    • DMSP Block 5D-1 Computer Controlled Spacecraft

      McElroy, Stephen M.; Gomberg, Louis; Beest, Roger Te; SAMSO; RCA/AED (International Foundation for Telemetering, 1979-11)
      The Defense Meteorological Satellite Program (DMSP) Block 5D-1 satellite is the first of a new generation of DMSP long life satellites to utilize onboard programmable computers for spacecraft control functions. During ascent and orbit injection the computers perform the navigation, guidance, and control functions autonomously; during on-orbit operations, they perform attitude determination and control, command and control, and miscellaneous other control functions, with only modest interaction from the ground. Four DMSP Block 5D-1 satellites employing these computer controls are currently on orbit and operational. On-orbit experience shows that performance has exceeded all expectations with respect to reliability and satellite life-time. In addition to providing the control functions for which they were designed, the computers have provided additional benefits by allowing the control systems to be reprogrammed from the ground to overcome hardware failure and degradation in other on-board components. This paper describes the DMSP mission, gives a brief overview of the integrated spacecraft system configuration, and provides the details of the control systems used in the various mission phases. The hardware and software portions of the control systems are described and some examples are provided showing how the reprogrammable capability allowed several orbital anomalies to be overcome and satellite life extended.
    • Dual Beam Single Axis Tracking Antenna for Tracking Telemetry Instrumented Airborne Vehicles

      Sullivan, Arthur; Electra Magnetic Processes, Inc. (International Foundation for Telemetering, 1979-11)
      A dual-beam, single-axis, tracking antenna capable of receiving and tracking telemetry data from an instrumented airborne vehicle is described. The dual-beam, single-axis, tracking antenna system consists of both a high-gain and a low-gain antenna positioned by the same antenna pedestal/servo electronics. Automatic switching between the high-gain and the low-gain antennas, based on received signal strength, permits tracking from maximum range (using the high-gain antenna) to close-in nearly overhead passes (using the low-gain antenna) by exploiting the wide-beam characteristics of the low-gain antenna when space losses are at a minimum. The wide beamwidth of the low-gain antenna permits its use as an acquisition aid for the high-gain antenna during initial acquisition, while its wide beamwidth also precludes locking on to a side lobe. The use of only one tracking axis rather than two reduces cost and improves reliability.
    • Error Control Strategies for High Rate High Density Recording

      Montgomery, R. C.; Sangamo-Weston, Inc. (International Foundation for Telemetering, 1979-11)
      Current trends in digital magnetic recording are expected to lead to increases in speed, linear density and track density. These increases generate conflicting requirements on error control hardware. This paper discusses the conflicts expected and current and future methods of solution.
    • Estimating Time to Develop Software

      International Foundation for Telemetering, 1979-11
      The most devastating task ever given to the computer system manager, is that of estimating the manpower and time to develop software. Software development has become almost completely out of control in terms of estimating the manpower and time needed for the complete job, from interpretation of the requirements to the operational readiness date. Just as the hardware design engineer never reaches the ultimate design and thus never concludes his job, so goes the software designer. The difference is, hardware design managers have grown up in this environment and therefore know the pitfalls and stopping points of producing a good, reliable product. The software design manager is less qualified because the field is relatively new, it is very complex, and computer hardware technology is expanding so rapid that software designers cannot catch up. This paper is designed to provide the software development manager categories and rules of thumb for estimating time and manpower requirements for each category of software development. In addition to establishing the standard milestones such as requirements definition, specification, design, coding, checkout, verification and validation, consideration is given on how to keep the Ford requirement from turning into a Cadillac capability.
    • Fundamentals of Heterodyne Detection in Laser Communications

      Goodwin, Frank E.; Hughes Aircraft Company (International Foundation for Telemetering, 1979-11)
      The use of optical heterodyne detection in a communication system requires a local oscillator laser beam to be coincident with the incoming signal on the detector. After detection, the signal behaves in every way like a classical microwave or radio signal which has been detected with a heterodyne receiver. This discussion of the use of optical heterodyne detection in laser communications thus includes consideration of modulation formats as well as the special geometrical requirements of combining the local oscillator and signal. Modulation formats of interest are amplitude modulation, frequency modulation and phase modulation, and both heterodyne and homodyne detection techniques are considered. The physical and geometric treatment of optical heterodyne detection is given. General equations are derived for the signal to noise ratio of a coherent receiver in terms of the distribution functions of the signal and local oscillator fields and the size of the detector. The most efficient local oscillator field distribution function is when it exactly matches that of the signal field distribution over the detector surface. A special case of interest is when the signal field is an Airy function and the local oscillator field is uniform. This special case is shown to be feasible with a small penalty in heterodyne mixing efficiency. An analysis of the heterodyne NEP includes factors from geometrical mixing efficiency, thermal noise, dark current, and electrical load mismatch. The degree of degradation is then a function of the amount of local oscillator power. Practical limits on heterodyne NEP's are established.
    • Future Modular Data Handling Concepts for Large Space Platforms

      Thompson, G. P.; ESA/ESTEC (International Foundation for Telemetering, 1979-11)
      With the ever-increasing competition for geostationary orbital positions, designers of applications satellites are looking more and more to the use of large multipurpose platforms to fly simultaneously a variety of payloads. This paper looks at the challenges these platforms provide in the field of data handling for individually launched and docking satellites, and reviews current European concepts and technologies which are being developed to meet these challenges.
    • Future Performance Limitations for Ground and Spaceborne Millimeter Wave Receiver Systems

      Cardiasmenos, Apostle G.; Alpha Industries (International Foundation for Telemetering, 1979-11)
      Recent developments in the technology for millimeter wave receiving equipment make a much more promising case for increased utilization of millimeter waves in telecommunication links. Low system noise figure coupled with large achievable antenna gain in small earth terminals make a good case for millimeter direct satellite broadcast links. Future technology trends indicate that use of the 80-100 GHz region of the spectrum will be beneficial and useful in the 1985-1990 timeframe.