Murphy, Carl; Science Applications, Inc. (International Foundation for Telemetering, 1981-10)
      Modern requirements for TMDE system diagnostics have led to the use of advanced computer testing methods which provide increased diagnostics power to the engineer and expanded functional operations for technicians. This paper describes these advanced computer testing methods of using hardware computer bus monitors which are human interfaced to allow routine operation and use of complicated computer and peripheral diagnostics by relatively low-training level technicians. This is a diagnostics support system which provides significant value through the human engineering, assurance of fix, and readiness of equipment. Real-time diagnostics monitoring during system operation is an operational feature which is discussed.

      Schoeck, Kenneth O.; Kobylecky, George M.; Range Systems Instrumentation; Federal Electric Corporation (International Foundation for Telemetering, 1981-10)
      Over the past few years, small desktop computers have been used more and more to control test equipment in various instrumentation evaluation applications. Computer control not only greatly reduces test time, but provides more consistent results by eliminating variations in individual test techniques. This paper describes a computerized system at the Western Space and Missile Center (WSMC), Vandenberg AFB, CA designed to automatically conduct IRIG compatible tests of instrumentation magnetic tape recorder/reproducers, analyze and print out the results. The system features remote or manual control of the various recorder types. Tests include harmonic distortion, frequency response, signal-to-noise ratio, flutter, time base error, interchannel time displacement error, intermodulation distortion, crosstalk and slot noise. The first six tests can be run individually or as a complete set designated as a “System” test.

      Amoroso, Frank; Hughes Aircraft Company (International Foundation for Telemetering, 1981-10)
      Although spread spectrum systems depend on large bandwidth to achieve performance, they must also operate within bandwidth constraints imposed by frequency allocations. The measures of bandwidth relevant to performance are usually quite different from those defined in frequency allocations. In this paper a number of definitions of bandwidth are discussed, and a number of direct sequence pseudonoise (DSPN) modulation techniques are evaluated according to those definitions of bandwidth. A wide range of bandwidths per chip rate result, and trades among the modulation types are given.

      Sabourin, Donald J.; Jirberg, Russell J.; Motorola Inc., Government Electronics Div.; NASA/Lewis Research Center (International Foundation for Telemetering, 1981-10)
      An on-board baseband processor concept developed for commercial communications satellite systems planned for the 1990s is described. The baseband processor, which operates in a time-division multiple access mode, provides significant advantages in improved link margins and system flexibility in accommodating varying demands from a large number of users because of its ability to route and control message traffic on an individual basis. This concept is currently being implemented in a proof-of-concept model with the main objective of developing the technology required to support detailed design and fabrication for an experimental satellite to be launched in 1987. This technology development includes serial MSK modems, Clos-type baseband routing switch, a singlechip custom CMOS maximum-likelihood convolutional decoder, and custom LSI implementation of high speed, low power ECL building blocks.

      Marshall, Donald L.; Hughes Helicopters, Inc. (International Foundation for Telemetering, 1981-10)
      Hughes Helicopters, Inc. is testing the U.S. Army AH-64 at the corporation’s facility at Carlsbad, California and at the U.S. Army Proving Ground, Yuma, Arizon. An automated telemetry system is being used to expedite the AH-64 qualification testing with minimum risk by providing on-line analysis of measured data. This paper discusses the special application software and hardware developed for this helicopter testing. The software and hardware is designed to provide timely engineering analysis of test measurements in order to minimize flight-safety risks, aircraft turnaround time, repeat testing, and developmental problem delays. The analyses include structural, dynamic, aerodynamic, weapons-systems, and aircraft-system considerations. Selected samples of real-time analytical displays generated on the system are included. The equipment and capabilities of the system which is being used in the testing will be discussed. The system has two analytical stations with display capabilities data of which can operate simultaneously on a single telemetered data stream or, alternatively, each station can operate simultaneously on separate data streams. Of interest in this paper are the spectrum of ground and flight operations required to enhance safety, to verify the attainment of test objectives, and to analyze the document test results. The acceptable time lag for analysis of measurement may vary considerably, depending on the purpose of the observation. Flight safety requires the fastest possible analysis, while several weeks may be acceptable for the documentation of results. For my purposes, then, I define real-time analysis as the attainment of engineering answers within a timeframe that will not impede the safe progression of the test. The analytical capability of our system utilizing telemetry is a significant step forward in the development of this current generation helicopter.

      Kruh, Pierre; THE AEROSPACE CORPORATION (International Foundation for Telemetering, 1981-10)
      Changes in the Navstar Global Positioning System (GPS) program in 1980 resulted in a reduction in the number of satellites from 24 to 18, and consequently led to a reconsideration of the original orbital configuration and a revision in the way buildup and replacement would be performed. During the buildup phase of the program, the Space Shuttle will be used, launching up to two Navstar satellites per mission on launches shared with other payloads and up to four satellites on dedicated launches. The original concept for the 24 satellite Navstar GPS constellation consisted of three orbit planes with eight uniformly distributed satellites per plane. In that configuration, all of the satellites on each Shuttle launch would be placed in only one plane. With the reduction from 24 to 18 satellites, it was determined that there were advantages to evaluating other constellations; rather than simply reducing the baseline three-plane, 24-satellite configuration to 18 satellites by removing two satellites from each plane, a larger number of planes may be preferred for the restructured program. Indeed, the current baseline configuration is a sixplane, 18-satellite constellation with three satellites per plane, and the three-plane constellation is an alternate configuration. Buildup and replacement studies for the new configurations that have been investigated have not only addressed the performance goals of Navstar GPS but have considered the economic use of the Shuttle as a launch platform. In addition, the launch constraints imposed by the Shuttle must be considered in the strategy used for buildup and replacement. This paper discusses the fundamentals of the buildup and replacement and the performance of the GPS with 18 satellites. The constellations discussed are the sixplane GPS baseline and the alternate three-plane configuration.

      CRAWFORD, MICHAEL A.; SWEITZER, RALPH F.; LORAL DATA SYSTEMS (International Foundation for Telemetering, 1981-10)
      The expanding requirement in Modern Telemetry Systems for Real-Time Data Processing has necessitated the commutation of a vast majority of the data processing functions into Front End Processors. Even the fastest of Host Processors has proven incapable of keeping pace with high speed data rates (up to 4 Megawords). The commutation of processing power into the telemetry front end has elicited the employment of distributive processing techniques in order to attain the desired throughput. A distributive processing system architecture achieves high processing throughput by apportioning data analysis functions. By defining and programming unique processing nodes to selectively acquire, distribute, compress, and/or convert data, extensive simultaneous operations are executable. Hardware merged bus structures have lent themselves conveniently to this method of data distribution and control. Conversely, conventional software structures are unsuited to distributive processing architectures which must support a broad spectrum of modular configurations. Primarily, this is evidenced when the composite system software must be repetitively customized as additional processing power or new capabilities are incorporated. Composite software that delivers a high degree of system configuration adaptability is nominally large and complex, is limited in application, depletes system memory resources and complicates sustaining software maintenance. In addition, an undesirable human interface is normally unavoidable with composite software since it requires that the user learn the specific front end system’s terminology and individual components. Bus Structure Software consigns itself to effectively support distributive processing techniques providing for adaptive system configurations. This disquisition will address the concepts of bus structured software and its application to distributive processing. Furthermore, this paper will discuss the architectural capability to service a wide range of telemetry users without specialized system tailoring. A typical implementation of this convention, the Advanced Decommutation System (ADS) designed by LORAL DATA SYSTEMS, San Diego, California will also be presented.

      Cardall, John D.; Cnossen, Richard S.; Magnavox Advanced Products and Systems Company (International Foundation for Telemetering, 1981-10)
      GPS has the potential of satisfying worldwide and local civil navigation requirements for Area Navigation (RNAV), Landings and Takeoffs under minimum ceilings and Advanced Air Traffic Control (ATC) Operations. Use of GPS in a differential mode in local areas is a key to achievement of this potential. This report describes the GPS system and its status; discusses GPS signal availability for the civil community; defines alternative differential GPS concepts; shows predicted performance enhancement achievable with differential GPS and the operational improvements which are expected.

      Lee, David J.; Guthrie, W. Coleman; McKee, Walter S., Jr.; COMSAT General Corporation (International Foundation for Telemetering, 1981-10)
      Both AT&T and GSAT are presently using the COMSTAR to expand and diversify their domestic public dial telephone networks. COMSAT General’s TTC&M earth station facilities at Southbury, Connecticut, and Santa Paula California, continuously monitor the status of the COMSTARs. For the purpose of increasing the likelihood of availability and maximizing the number of communications transponders to the users, at the end of the spacecraft design lifetime, COMSAT General was able to reach a business agreement with AT&T and obtain FCC authorization to launch COMSTAR D-4 and colocate D-1 and D-2. Therefore, as far as the communications earth stations are concerned, colocated D-1 and D-2 with a coordinated 24 TWT configuration are technically identical to a single COMSTAR satellite. There is, however, a significant increase in satellite lifetime due to reduced solar array and battery loading (about half) since each satellite now operates with twelve TWTs on instead of the usual twenty-four for a COMSTAR. This paper will describe the TTC&M earth stations’ modification to accommodate the colocated satellites. Operational considerations and some actual operational experience will also be discussed.

      Tremain, George F.; Layton, Jerry; Decom Systems, Inc. (International Foundation for Telemetering, 1981-10)
      This paper will describe the enhancement to the man-machine interface brought about by the use of color CRT’s in a real time, de-centralized telemetry processing system. The use of a microprocessor controlled telemetry system allows equipment set-up and various data outputs displayed using an off the shelf intelligent color terminal. The use of color annotated messages and graphics allows a more effective interaction between the operator and the system.

      Wasse, Michael P.; European space Technology Centre (International Foundation for Telemetering, 1981-10)
      This space mission will investigate the structure of the comet by passing close to the nucleus. The spacecraft will first be injected into a geostationary transfer orbit where a perigee boost motor will deliver the kick necessary to encounter the comet post perihelion, as it passes through the ecliptic plane at a distance of 0.98 AU from the earth. The spinning spacecraft and the use of a shield for protection from the dust present in the comet atmosphere dictate the use of a despun high gain antenna with inclined beam. The telemetry downlink at 40 KBps is in X Band and will be received on the Parkes (Australia) radio telescope which will be specially adapted for the task. The trade offs leading to the selected communications configuration are described along with the various spacecraft hardware items such as antennas, transponder, decoder and twta.

      Carpenter, W. D.; Naval Ocean Systems Center (International Foundation for Telemetering, 1981-10)

      Pentlicki, Chester J.; Esch, Fred H.; COMSAT Laboratories (International Foundation for Telemetering, 1981-10)
      Continuing growth in domestic and international communications traffic indicates a need for expanded communications satellite capacity. The size of spacecraft for the 1980’s has been established and design concepts to meet the increased capacity of the 1990’s are under consideration. Launch vehicle capability permits alternatives to single-purpose spacecraft for the new era. Multipurpose spacecraft platforms and clustered satellites are concepts with unique advantages. Platform concepts will be seen in the 1990’s, and growth in technology will permit dedicated spacecraft to achieve new levels of capacity. Technical advances in the 1990’s will include extended spacecraft lifetime possibly enhanced by refurbishment of payloads. Technical capability may well exceed the ability of institutions to utilize it, and innovative arrangements, including participation of financial institutions, may be required to fully exploit the improved technology. In this paper, influential factors, such as multiple narrow-beam antennas coupled with precise pointing, are appraised in terms of design consequences and their impact on spacecraft subsystems is identified.

      Basuthakur, Sibnath; General Electric Company (International Foundation for Telemetering, 1981-10)
      To insure a reliable performance of any spacecraft over its long mission life, a thorough and coordinated attitude control subsystem testing must be conducted. The three axis motion Simulator-Hybrid computer facility at General Electric has provided the capability of testing the Attitude Control Electronics (ACE) for various satellite programs including Japanese satellite program BSE and Defense Communication Satellite DSCS-III. Although the facility has provided complete verification of analysis and simulation of all operating modes in a closed-loop fashion, the checkout procedure has proven to be extremely timeconsuming. It requires real time dedicated computer support. In addition, limited sensor field of view may, in some instances, limit the scope of the test. The objective of this paper is to underline an alternate philosophy of the subsystem testing that has been extensively used to qualify the DSCS-III flight control system under various environments. It is designed to compare, on a bit by bit basis, all critical controller internal and output parameters between the flight control algorithms embedded in the ACE and a validated simulator controller. The simulated controller (truth model) is validated after careful analyses and simulation of all operating modes under all possible initial conditions. All controller parameters to be compared are assigned to CPU test port and the telemetry port. This computer-aided testing program is used to process CPU output data in an off-line autonomous basis to validate the control algorithms embedded in the ACE.

      Thibodeau, Lionel; Lt. Col. Fornwalt, Harry C.; The Aerospace Corporation; USAF Systems Command (International Foundation for Telemetering, 1981-10)
      The Consolidated Space Operations Center (CSOC) is being designed by the Air Force Systems Command Space Division to centralize all Department of Defense Space Shuttle and satellite operations within a single secure facility. CSOC will be located near Colorado Springs, Colorado. It will provide DOD with enhanced space command and control capabilities in the late 1980s and 1990s. It will include a Satellite Operations Complex (SOC), a Shuttle Operations and Planning Complex (SOPC), and communications, facilities, and support segments. An initial operational capability is planned for mid-1986 that will include appropriately selected portions of SOC, SOPC, and the integrated segments. These early limited capabilities will be expanded in the late 1980s to satisfy the requirements of the DOD mission model. SOC will share command and control of space satellite missions with the Satellite Test Center (STC) in Sunnyvale, California. The STC is part of the Air Force Satellite Control Facility (AFSCF). Both the STC and SOC will control assigned satellite missions using the AFSCF remote tracking stations located at seven sites around the world. SOC will be functionally equivalent to a portion of the STC as improved by the data systems modernization program. SOC and STC will be interoperable to permit mutual backup in the event of an extended failure at either center. SOPC will be functionally equivalent to portions of the Shuttle operations complex at the NASA Johnson Space Center (JSC). It will provide for flight planning, flight readiness, and flight control of DOD Shuttle flights. As with SOC and STC, SOPC and JSC flight control facilities will be able to provide critical backup support to each other in the event of an extended failure at either center. External wideband communications circuits at CSOC will interface with both NASA and Air Force space facilities, such as the eastern and western launch sites, JSC, and the AFSCF remote tracking stations. Satellite relay techniques using both Defense Satellite Communication System (DSCS) satellites and Domestic Communications Satellites (DOMSAT) will be the basic method of network communication. Dedicated narrowband circuits, provided by leased lines accommodating both voice and data, will interface mostly with other Air Force space facilities. This paper discusses the CSOC program background, configuration, operations concept, external interfaces, and acquisition status.

      Layland, J. W.; Yeater, M. L.; McClure, D. H.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1981-10)
      The Networks Consolidation Program (NCP) was established by NASA in the fall of 1979 to accomplish the consolidation of the two NASA Ground Tracking Networks into a single unified network. Consolidation of the two networks had been recommended by an all-Networks NASA planning group and presented to NASA top management in October of that year. The consolidated network of 1986 will make use of facilities that are now included in the Goddard Ground Spaceflight Tracking and Data Network as well as the existing JPL Deep Space Network. These facilities will be combined and modified to provide a consolidated network that is capable of supporting the set of planetary and high earth orbiter missions that are planned for that era. The drivers for the development of the consolidated network are both technical and economic. The consolidated network must provide the increased sensitivity needed to support the Voyager 2 spacecraft at its distant encounters with Uranus and Neptune in 1986 and 1989. It must provide support to spacecraft in high earth orbit and at the nearby planets at data rates which may be a factor-of-ten higher than present deep space data rates. And it must do both with significantly less cost for maintenance and operation than the sum of the separate networks would have cost in the late 1980’s. This report traces the history of activities and events that led to the decision to consolidate the NASA ground tracking and data networks. It also presents a summary of the planned evolution of the NASA ground tracking networks, from the time of decision in October 1979 through the mid 1980’s. It is an updated version of a report presented at the AIAA/NASA symposium on Space Tracking and Data Systems, June 1981.

      Lennox, William M.; Microdyne Corporation (International Foundation for Telemetering, 1981-10)
      The conventional AGC weighted diversity combiner design experiences performance problems in the presence of fast fade rates of amplitude and phase of RF input signals. These problems and other needs are discussed by the author in detail along with the design and theory of a new combiner that has been developed. It successfully overcomes these phase and amplitude fading problems and also addresses many other problems such as the need for wider bandwidths, computer control, and many other improvements. These improvements are necessary to increase the state-of-the-art in the telemetry and communications combiner. The design criteria and realization of the design goals are described in detail accompanied by a block diagram discussion of the theory of operation.

      Wilkins, G.; Nakagawa, A.; Kamikawa, N.; Baldwin, D.; Couch, P.; Naval Ocean Systems Center Hawaii Laboratory; ITT-EOPD (International Foundation for Telemetering, 1981-10)
      Fiber optics’ major contributions to undersea communications should include greater telemetry bandwidth, improved data precision and a decrease of system volume. The last two of these served as primary goals during recent design, fabrication and ocean testing of an undersea, electro-optical (E-O) telemetry system. The system’s total length was nearly 70 km. It contained 8 in-line repeaters which were powered through the E-O cable. Data were transmitted full duplex (22 MB/s at 0.83 μm & 43 KB/s at 1.06 μm through a single optical fiber. Power consumption was 1.69 watts for each repeater. Telemetry BER through the 70-km cable path was better than 10^-9 at 22 MB/s. The repeater housings were designed for 1-km ocean depths. Their dimensions (including bend-limiting cable terminations) were 2.88-cm diameter by 30.5 cm length. Each repeater contained special circuitry so that it would be queried from shore in a fault diagnosis mode. Designs and performance are reported for the E-O telemetry system and for its major components.

      Knowles, Robert C.; Moore, John M.; Woodworth, Donald J.; Magin, Greg A.; Microdyne Corporation (International Foundation for Telemetering, 1981-10)
      This paper describes some design features of a new microprocessor controlled, single channel telemetry receiver which will have use in the automated telemetry systems beginning to emerge. The parameters controlled, and the methods used to interface the receiver with the controller or another slave receiver to create the equivalent of a dual channel remote controlled receiver are discussed. A general description of the software utilized by the receiver is included. A new four bandwidth FM demodulator is described which utilizes modern technology to provide FM demodulation over the full range of receiver IF bandwidths. It features a high gain limiter having excellent output waveform symmetry and a linear phase detector with PIN diode switched linear phase shift networks to realize a demodulator exhibiting excellent linearity. A wide angle PM demodulator is also described which features a novel antisideband circuit utilizing PM feedback to essentially unmodulate the received signal and thereby prevent sideband lock.

      Kline, E. Lee; Naval Research Laboratory (International Foundation for Telemetering, 1981-10)
      This paper represents some considerations resulting from work conducted during a Navy study of secure voice system alternatives and the development of military communication systems. It begins by identifying a set of attributes for a “goal” military communication system. The paper then presents a realizable communication system concept which could be used as a basis for a future system design. The concept is based on an embedded multiple rate system where a basic mode, supported at the lowest transmission rate, is enhanced using additional transmission capacity, when it is available, to support a higher rate. The conclusion discusses the impact of this concept on some of the functions a military communication system must perform.