• THE TECHNOLOGIES OF AUTONOMOUS SPACECRAFT MAINTENANCE

      Elowitz, Murray L.; Wong, Bill C.; TRW Space and Technology Group (International Foundation for Telemetering, 1981-10)
      Autonomous spacecraft maintenance (ASM) is the term used to describe the capability of a spacecraft to perform its maintenance functions without frequent, regular ground support and interactions. This new spacecraft attribute is needed to enhance the survivability and availability of our satellites, as well as to reduce operational support costs. This paper explains the concept of ASM as it has evolved. Generic requirements are given and explained for a latter 1980's capability. Spacecraft architectural changes are required, involving a mixture of technology adaptation and advances. Technology developments required to meet the requirements are identified and assessed. Significant advances are needed in system and subsystem technology areas to create a posture for building an ASM capability. With WWMCCS increasing reliance on spacecraft for both communication and sensor data, the issues of ASM are of vital importance to this community.
    • AN INSIDE VIEW OF PSEUDORANGE AND DELTA PSEUDORANGE MEASUREMENTS IN A DIGITAL NAVSTAR GPS RECEIVER

      Ward, Phil; Texas Instruments Incorporated (International Foundation for Telemetering, 1981-10)
      The goal of this paper is to develop insight into the real-time nature of GPS observables measured by a digital receiver. The concept of how independent pseudorange and deltapseudorange measurements are captured as a by-product of the code and carrier tracking loops of a digital NAVSTAR GPS receiver is explained. The classical equations defining true range and delta range are derived in terms of pseudorange and delta pseudorange. The actual GPS receiver measurements are then related to these equations. The difference between GPS measurement resolution and precision is treated and the sources of the GPS receiver contribution to the total GPS error are identified. The total GPS error, in terms of user equivalent range error (UERE) and user equivalent delta range error (UEDRE), is characterized. However, an unaided GPS navigation process can filter out only the unbiased random error in the observables, not the total UERE and UEDRE content. Also, the random error in GPS observables is not stationary. Hence, the random error in UERE and UEDRE is identified and characterized.
    • THE PARTICULATE NOISE POWER SPECTRUM OF A MAGNETIC TAPE RECORDER/REPRODUCER

      Hedeman, Walter R., Jr.; Law, Eugene L.; Pacific Missile Test Center (International Foundation for Telemetering, 1981-10)
      This paper presents a theoretical derivation of the noise power spectrum of a magnetic tape recorder/reproducer. The theoretical results are shown to be in good agreement with experimental data.
    • SPACE RADIATION HARDENING AND VLSIC TECHNOLOGY

      Josephson, Vernal; The Aerospace Corporation (International Foundation for Telemetering, 1981-10)
      Military Space Systems are required to have a certain level of immunity to all possible space radiation effects experiences during mission life time. These include upset and latchup from weapon x-ray bursts and cosmic rays, photo current burn-out of active junctions by large prompt doses of radiation, and performance degradation from accumulated dose due to enhanced radiation belts. Procuring piece parts capable of performing mission requirements and providing the desired immunity to these effects, and testing to verify the desired satellite immunity presents problems which must be considered when contemplating massive use of VLSIC technology where even higher desired levels of immunity may be desired. The techniques used for hardening and the testing required for hardness assurance will be discussed with emphasis on their application to VLSIC technology and its potential in space applications. An overall satellite was subjected to irradiation in order to verify its immunity to space radiation. These results will be discussed below.
    • THREAT-RESPONSIVE SURVIVABILITY AND SPACE WARFARE AT HIGH ALTITUDES

      McPherson, Donald A.; Science Applications (International Foundation for Telemetering, 1981-10)
      The US is being denied effective use of space systems for tactical support of combat operations because of doubts regarding the survivability of space missions in hostilities. Space systems survivability has been the object of widespread analysis and development for fifteen years. Because survivability is expensive, the decision to make the necessary substantial investments for high-altitude satellites will be postponed until there is tangible evidence that the threat is developing into anti-satellite weapon systems. Therefore, space system development and acquisition must be formulated so that the appropriate survivability investment can be made as the physical attack threat at high altitudes eventually emerges.
    • COLOCATED COMSTARS

      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.
    • TWO AXIS CLOSED-LOOP ANTENNA POINTING FOR A DUAL-SPIN SPACECRAFT

      Smay, John W.; Hughes Aircraft Company (International Foundation for Telemetering, 1981-10)
      This paper describes the control and sensing techniques and practical implementation used to obtain precision antanna pointing on a class of commercial communication satellites. The basic spacecraft bus is a dual-spin gyrostat with momentum of order 1500 ft-lb-sec. Spin is about a minimum axis of inertia and active damping using the despin motor and platform product of inertia is employed for nutation stabilization. Using two axis RF beacon tracking, steady state pointing accuracy exceeding 0.025° (3σ) in roll and pitch and 0.1° (3σ) in yaw is achieved. This accuracy is approached during orbit and attitude trim thrusting maneuvers as well.
    • TDRS ANTENNA AUTOTRACK LOOP

      Schmeichel, Harry; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1981-10)
      The Tracking Data and Relay Satellite (TDRS) has two large, gimballed antennas which will relay information between earth-orbiting satellites and a ground terminal in New Mexico at data rates up to 300 million bits per second. This relay service requires closedloop tracking of user satellites at K-band frequencies with a pointing accuracy of 0.06°. An autotrack loop, closed through a ground-based computer, performs this RF beam pointing function for each single-access (SA) antenna. The autotrack system basically consists of two stepper motors to move the antenna, an onboard RF monopulse system to sense the pointing error and command generation equipment on the ground to close the loop. It is shown how system models and observations are combined to stabilize and improve the pointing performance of this lowbandwidth, closed-loop tracking system. Antenna pointing performance is demonstrated by simulation.
    • A METEOROLOGICAL COMMAND AND CONTROL SYSTEM

      P. L. Greening; Kinney, T. W.; Shaw, T. R.; HARRIS CORPORATION (International Foundation for Telemetering, 1981-10)
      There are many functions required to command, control and maintain the health and welfare of a meteorological satellite and acquire payload sensor data in a real time scenario. This paper describes the functions and performance of a specific meteorological command/control and telemetry processing system. Further, this paper describes the communications networks which link the various command/control, telemetry, and user ground stations together. A description of the user sensor data is also presented.
    • A GENERAL APPLICATION REAL TIME PROCESSING AND DISPLAY SYSTEM

      Schumacher, G. A.; Sangamo Weston, Inc.-Data Systems Division (International Foundation for Telemetering, 1981-10)
      A general purpose system for the processing and display of telemetry data is described. The system uses a DEC PDP-11 mini-computer as the system processor. Systems of this type implemented in the past generally had limited data processing capabilities due to high data rates and limited CPU power. The Real Time Data Monitor System (RTDMS) is designed to maximize the data processing capability by teaming the CPU with a pre-processor. A total hardware/ software system was designed which is structured around certain commonly required classes of data. The system minimizes the processor overhead associated with each class thereby freeing time for useful processing. A complete software system was implemented which takes full advantage of the RSX-11M multi-task operating system. Because of the substantial data base required to configure the system, particular attention was given to the operator interface. A set of programs were implemented which construct all data base files required using interactive menus. Operator input is minimized as well as the training time required to set-up the system.
    • ACQUISITION, PROCESSING, AND APPLICATIONS OF METEOROLOGICAL SATELLITE DATA AT THE AIR FORCE GLOBAL WEATHER CENTRAL

      Major Johnson, William R.; HQ Air Weather Service (MAC) (International Foundation for Telemetering, 1981-10)
      The Air Force Global Weather Central (AFGWC) is the world’s largest military meteorological facility. A large portion of its men, women, and computer resources are dedicated to the acquisition, processing, display, and application of meteorological and space environmental data. In this paper, I will address only meteorological and space environmental data.
    • DMSP PRIMARY SENSOR DATA ACQUISITION

      Lieske, Roger W.; Westinghouse Aerospace Divisions (International Foundation for Telemetering, 1981-10)
      A Data acquisition system which provides global pictorial cloud cover data for operational military meteorological purposes is described with emphasis on significant design features. These features include near constant geometric resolution through use of an oscillating scanner and variable instantaneous field of view (IFOV), thermal infrared channel output linear with temperature, visible wavelength sensitivity continuous from sub-solar to sublunar, along scan gain control permitting albedo images through the terminator, glare suppression enabling sensing of nighttime scenes in the presence of solar illumination on the spacecraft, wow/flutter correction of video data sampling to that of a reference scan motion, and dual geometric resolution capability from a single detector by synthesis of low resolution data.
    • SATELLITE CONFIGURATIONS FOR EHF* COMMUNICATIONS FOR MOBILE TERMINALS

      McElroy, D.R.; Niessen, C.W.; Massachusetts Institute of Technology (International Foundation for Telemetering, 1981-10)
      The planners of military and commercial satellite communications (SATCOM) systems for the 1980’s are considering the use of the Extremely High Frequency (EHF) band, especially those allocations from 17- to-45 GHz1. The wide bandwidths available at EHF can be used for higher capacity systems to meet projected future service requirements and for spread spectrum modulation techniques for interference rejection and/or multiple access purposes. Evolution into these higher frequencies also offers the opportunity to develop systems and signalling structures which are functionally common across multiple user communities. Such techniques provide interoperability possibilities while allowing more efficient use of space assets and minimizing the number of unique terminal developments. Due to user-platform space and prime power limitations as well as to terminal production, installation, and maintenance costs for large user populations, it is also important that EHF system configurations accommodate small, low-power terminals. One such approach involves departing from traditional SATCOM designs by incorporating increased satellite sophistication for reduced terminal size and complexity requirements. The associated spacecraft would employ advanced technologies such as uplink antenna discrimination., on-board signal processing, and downlink beamhopping. This paper presents some system configuration options for providing EHF service to mobile terminals and indicates implementation possibilities for the major spaccraft payload subsystems, with emphasis on some configuration options for the on-board signal processing unit.
    • ADVANCED 14/12 AND 30/20 GHz MULTIPLE BEAM ANTENNA TECHNOLOGY FOR COMMUNICATIONS SATELLITES

      Chen, C.C.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1981-10)
      This paper discusses recent TRW advances in communications satellite antenna technologies for the 14/12 and 30/20 GHz bands. The 14/12 GHz antenna system provides 15 or more high gain, low sidelobe spot beams for contiguous coverage of the CONUS for point-to-point communications, or four contoured time zone beams for direct broadcast service. A 2-meter offset reflector has been built and tested to demonstrate the frequency reuse and beam isolation capabilities of the antenna. The 30/20 GHz antenna system provides 10 to 20 fixed beams for large volume traffic trunking service and six independently scanned beams for customer-premise-service within the CONUS. A proofof- concept model antenna for proving the technology feasibility is currently under development.
    • PREPROCESSING IN TODAY’S TELEMETRY COMPUTER SYSTEM

      Hildebrand, Graham; Sangamo Weston (EMR Telemetry) (International Foundation for Telemetering, 1981-10)
      An increasing number of processes are being moved from the host computer to a versatile, smaller front end preprocessor. This paper discusses the reasons for preprocessing and presents a general purpose preprocessor. Use of the preprocessor in mapping MIL 1553 Multiplex Bus data is described as well as the more routine tasks of data merging and identification, compression, engineering units conversion, array forming, and data sorting.
    • NATO TEST AND EVALUATION RANGE STAVANGER, NORWAY

      Dahl, Ernest A.; NATO PUTTS System (International Foundation for Telemetering, 1981-10)
      The NATO Test Range at Stavanger, Norway permits cold environment testing of NATO Systems, common TLM data processing for many types of missiles, with both ship/shore control as well as evaluation. Figure 1 shows the location.
    • SCIENCE AND APPLICATIONS SPACE PLATFORM COMMUNICATIONS AND DATA MANAGEMENT SYSTEM

      Kasulka, L. H.; McDonnell Douglas Astronautics Company (International Foundation for Telemetering, 1981-10)
      The development of space platforms represents the next logical step in the exploration and utilization of space. Such platforms promise cost-effective means for performing both scientific and applications missions, such as surveys of Earth resources, for example, in low Earth orbit. Payloads mounted on these platforms can perform missions for longer periods of time than are currently available to payloads mounted in the Shuttle’s payload bay. In addition, these platforms can provide a variety of services, including a centralized power source, command and data acquisition, communications, pointing and environmental control, as well as periodic Shuttle visits for performing maintenance tasks, replenishing consumables, and replacing payloads. These platforms must be able to provide data and communications services to groups of payloads consisting of individual payloads that may or may not have common objectives and operating characteristics, and where the payload mix on a platform changes periodically during the orbital life of the platform. Appropriate data systems can be provided to support a platform development program and modest extensions of existing technology will allow these platforms to accommodate the evolution of payloads foreseen through the 1980’s.
    • BUS STRUCTURED SOFTWARE FOR A MODERN PCM DECOMMUTATOR

      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.
    • NAVY ENVIRONMENTAL DATA DISTRIBUTION

      WOOLDRIDGE, FRANCIS R.; NAVY SPACE SYSTEMS ACTIVITY (International Foundation for Telemetering, 1981-10)
      The distribution of environmental data by the Navy Oceanography Command to support worldwide fleet operations is discussed. The fact that these operations are being conducted from platforms which are under sea, on the ocean surface and in the air, forms the basis for a variety of unique distribution methods. The organization of the Naval Oceanography Command is shown along with the fleet units operating with geophysics personnel attached. Methods of distribution include data sources to support the generation of numerical products and tactical operations. Fleet communications links are described including the data processing systems being installed at shore stations and onboard ships.
    • A PROGRAMMABLE-SIGNAL CONDITIONING PULSE CODE MODULATED TELEMETRY ENCODER

      ECKSTEIN, HOWARD M.; MICROCOM CORPORATION (International Foundation for Telemetering, 1981-10)
      The development of variable format airborne PCM data acquisition systems has generally been predicated upon advances in the field of solid state memory device technology. The introduction of Electrically Eraseable Programmable Read Only Memory (EEPROM) devices has generated renewed interest in the design of fully programmable PCM encoders. This paper will describe the evolution of one such micro-miniature PCM encoder system incorporating the following features: ∙ Complete Frame Format Program Capability ∙ Software Controlled Single Ended/Differential Input Program Capability ∙ Individual Sample - Gain/Offset Scaling Capability ∙ Hard Wire Program/Erase/Program Capability ∙ Variable Word Resolution ∙ Small Size