• 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.
    • TDRSS ANTENNAS GROUND STATION AND SPACEBORNE

      Butts, C. J.; Gutwein, T. A.; Harris Corporation (International Foundation for Telemetering, 1981-10)
      Three sixty foot diameter Ku-Band Antennas have been completed as part of the Tracking and Data Relay Satellite System (TDRSS) at the NASA Johnson Space Center, White Sands Test Facility. These very high efficiency satellite communication antennas provide in excess of 68dBi directivity. Further characteristics include autotrack accuracy of 0.01E, frequency reuse, and surface accuracy within less than .02" rms of the desired shaped surface. Two TDRSS antennas weighing less than 52 pounds are ready for launch aboard each satellite. These 16 foot deployable antennas provide frequency reuse performance in two frequency bands - Ku and S. As with the sixty foot antenna, shaping of the subreflector and main reflector is utilized to achieve high aperture efficiency. This paper describes some of the design, analysis and measurement techniques used in the development of these antennas.
    • TDRSS CONTROL NETWORK

      Manders, Robert H.; TRW Defense Systems Group (International Foundation for Telemetering, 1981-10)
      The new NASA near-earth orbit tracking and data acquisition network will be made up of a network of two, synchronous orbit, tracking and data relay satellites plus an in-orbit spare. The principal ground components are the TDRSS White Sands Ground Terminal (WSGT) near Las Cruces, New Mexico and the Network Control Center at NASA GSFC in Greenbelt, Maryland. Communications between the sites are handled via the NASA Communications Network (NASCOM) through the NASA Ground Terminal (NGT) located at the WSGT. This paper will discuss the control of the TDRSS Network for User Spacecraft Tracking and User Data Acquisition.
    • TDRSS GROUND SEGMENT PERFORMANCE

      Matchett, M.W.; Government Communications Systems Division (International Foundation for Telemetering, 1981-10)
      About 150 racks of fully-automated equipment provide tracking, user traffic transmission and reception, simulation, and verification services for users of NASA’s Tracking and Data Relay Satellite System (TDRSS). Installation of this equipment in the White Sands Ground Terminal Facility is now complete and final testing is nearly complete. This paper describes the implementation and performance of that portion of the ground segment equipment provided by Harris. Major equipment groups described are 1) antennas, 2) user traffic link forward (transmit) equipment, 3) S-band single-access return (receive) equipment, 4) K-band single-access return equipment, 5) multiple-access RF equipment, 6) range and range-rate equipment, 7) user spacecraft simulation equipment, and 8) system verification equipment.
    • 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.
    • TECHNOLOGY DEVELOPMENT FOR A K-BAND BEAM-HOPPED SATELLITE DOWNLINK

      Berglund, Carl D.; Dolbec, Richard E.; Stevens, Mark L.; M.I.T. Lincoln Laboratory (International Foundation for Telemetering, 1981-10)
      A beam-hopping system utilizing a phased array and solid-state power amplifiers has previously been introduced for application in EHF communications satellites. The performance of a 5-bit P-I-N-diode phase shifter developed for use at 20 to 21-GHz is presented. The development and characterization of 0.5-W K-band GaAs MESFETs is discussed together with their performance capability. The performance of experimental amplifier designs is included.
    • Telemetering Standards Coordination Commitee

      McAnally. Claude W. (International Foundation for Telemetering, 1981-10)
    • TELEMETRY AND TELECOMMAND DATA PROCESSING FOR THE GERMAN SPACE PROGRAM

      Piotrowski, Peter; German Space Operations Center (International Foundation for Telemetering, 1981-10)
      The data system for the processing of telemetry and telecommand data for the German space research program is in the process of being implemented. It consists of data processing, monitoring and transmission facilities including hardware and software at the ground station with various antennas and at the mission control center. The system is designed on distributed processing techniques based on processors of various sizes. The software is modular and can easy be adjusted for the various mission requirements. Data transmission is based on. standard protocolls.
    • TELEMETRY PROCESSING FOR THE AIR FORCE SATELLITE CONTROL FACILITY

      Michaud, Colonel Normand; HQ Air Force Satellite Control Facility (AFSCF) (International Foundation for Telemetering, 1981-10)
      This paper describes the telemetry processing capability of the Data System Modernization (DSM) system being developed at the Air Force Satellite Control Facility (AFSCF) for real-time or off-line processing, storage, and display of satellite telemetry data. The system accepts multiple satellite streams from the AFSCF Remote Tracking Stations (RTS) through a wide-band communications segment to the communication interface support equipment (IBM Series 1 computers) for processing analysis and display in the Mission Control Complexes (MCC). Dual IBM 370 series computers process the telemetry data for real-time command and control, while archiving on the disk and tape for future mission planning and post flight analysis. Real-time displays are located in the MCC’s or program dedicated work areas. The network is configured for support by RCC where generic checkout of the entire data distribution and telemetry system is performed prior to release for mission support to an MCC. The system is designed for the large diverse satellite population of the AFSCF with growth for future requirements.
    • TELEMETRY SOFTWARE DEVELOPMENT LIFE CYCLE

      Campbell, Alan B.; ABC Systems, Inc. (International Foundation for Telemetering, 1981-10)
      All orderly software development proceeds through the phases of a predictable life cycle. This behavior is characteristic of telemetry software development, also. Each phase of the life cycle is definable in terms of specific milestones. Understanding the life cycle is crucial for accurate estimation of time and effort, as well as for producing reliable software on time and within budget.
    • TELEMETRY-, TELECOMMAND- AND MONITORING SYSTEMS OF EUROPEAN SATELLITE CONTROL STATIONS

      Fröhlich, Horst; Borgmeyer, Johannes; Dornier System GmbH (International Foundation for Telemetering, 1981-10)
      Since years Dornier System have been active, for the European Space Agency (ESA), in the field of development and manufacturing of baseband equipment for Satellite Control Stations. Respective Telemetry- Telecommand- and Station Monitoring Systems have been designed on the basis of microprocessor controlled units which are interconnected by standard interfaces in order to facilitate station integration procedures. The equipment will be integrated in all European Satellite Control Stations of the existing and coming generation. The paper describes the different subsystems its interfaces and software structure.
    • THE TELESAT CANADA TRACKING, TELEMETRY AND COMMAND SYSTEM

      Turner , S. Barry; Telesat Canada (International Foundation for Telemetering, 1981-10)
      The Telesat Canada Tracking, Telemetry and Command (TT&C) System was developed to provide the Company with a system for geostationary orbit control and a dedicated capability for transfer orbit operations. For C-band (6/4 GHz), Telesat has evolved a costeffective mix of facilities based on a single tracking antenna and shared use of communications antennas, supplemented by low-cost fixed antenna systems. The satellite expansion program into Ku-band (14/12 GHz) required a parallel development of TT&C facilities. A unique feature of this development was the conversion of an existing 11-meter C-band antenna into a dual C- and Ku-band antenna, with a monopulse tracking system, employing an offset feed and tilting subreflector technique. Additional fixed Ku-band antenna systems were required to generate reliable beacons for RF sensor control of the communications antennas on the Anik C satellite, in the presence of deep fading conditions. This need, combined with a requirement for a long baseline for range measurement, resulted in the development of geographically widely separated, remotely operated T&C facilities. This paper is a description of the special features and performance of the Telesat TT&C System.
    • THEORETICAL AND PRACTICAL ASPECTS OF OPTIMIZATION IN FINITE WORD-LENGTH DIGITAL SIGNAL PROCESSING

      Pollara-Bozzola, F.; Yao, K.; Univ. of California (International Foundation for Telemetering, 1981-10)
      We consider a general class of digital signal processing problems in which some sytem parameters restricted to some finite set of values are selected based on the minimum meansquare error criterion. This class of problems are relevant in the design of modern communication, radar, and antenna array systems under finite word-length con-constraints. Linear problems allowing infinite precision values are given by the classical Wiener solutions. However, under the finite word-length constraints, optimum solutions can be obtained in principle by using techniques from integer quadratic programming problems. Practical solutions obtained in this manner, such as from the branch-and-bound algorithm, usually use a large amount of active computer memory space and thus are not applicable to real-time on-board processing situations. In this paper, we shall consider various theoretical and practical aspects of exhaustive search algorithms over shrinking sequences of constrained regions known to contain the desired optimum solution. Properties and bounds on the number of points to be searched as well as specific system problems shall be presented.
    • 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.
    • THROUGHPUT DELAY FOR MIXED-LENGTH, MIXED-PERIOD PACKETS WITH BUSY-SENSE MULTIPLE-ACCESS PROTOCOL

      Krause, Lloyd O.; Rockwell International (International Foundation for Telemetering, 1981-10)
      Packet TM of asynchronous multi-instrumented spacecraft requires framing of packets having different lengths and different arrival intervals. A similar situation would occur in a general message networking application with messages of arbitrary length and arrival rate at a network node. Use of a bus-system for packet transfer, or an order wire for message transfer, requires a minimum rate of status inquiry, and of data read rate, to insure stability and non-overloading. Our paper offers a rather general, but compact, throughput delay analysis suited to packet characteristics from uniform to source-dependent period and length. Arrival probability may vary from “soft” or uniform to “hard” arrival induced by slotted delay. The arrival probability is modular in source packet-period. A closed solution form, though expressible, is not tractable, and a recursive solution was used to obtain numerical results. Computed throughput delays for various combinations of identical sources and mixed sources are illustrated. For identical sources, under “hard” periodic arrival probability, channel slotting is desirable to maintain channel capacity. Some comparative results are offered. For mixed sources with source-dependent packet length and rate, slotting may not be feasible or efficient. Only read-rate controls the expected throughput. The analysis and results shown should prove helpful both to further study and present application of packet TM and message networking.
    • TOMAHAWK CRUISE MISSILE SAFETY OF FLIGHT VIA RF LINK

      Blackwood, Joe R.; Cruise Missile Systems (International Foundation for Telemetering, 1981-10)
      The Tomahawk cruise missile is configured for launch from a submarine, surface ship, or ground installation. The boost-phase propulsion is supplied by a jettisonable, solid-fuel booster engine. Upon jettison of the booster, an airbreathing, liquid-fuel turbofan engine is ignited to provide propulsion for the duration of the flight. Flight control is autonomous. The development of a program such as the Tomahawk requires that missiles be configured for test flights. These configurations require telemetry and tracking systems to aid in flight performance evaluation and an RF link range safety command system to provide for safe conduct of the flight. The subject of this paper is the range safety command system with emphasis on emergency commanded flight termination, automatic flight termination modes, remote flight control capability, and prelaunch checkout of the system.
    • THE TRACKING AND DATA RELAY SATELLITE SYSTEM: AN OVERVIEW

      Davis,Malcolm G., Jr.; TRW Defense and Space Systems Group (International Foundation for Telemetering, 1981-10)
      The Tracking and Data Relay Satellite System (TDRSS) is a shared service system supplying leased communication and tracking services to NASA and commercial Advanced Westar channels to Western Union and the American Satellite Company. An overview of the TDRSS design is presented. The space segment, consisting of four geosynchronous satellites, is described including launch. The spacecraft is described with emphasis on the communications payload covering both the NASA TDRSS and Advanced Westar equipment. The ground terminal located at White Sands, New Mexico, serves as the interface between the four TDRSs and up to 32 user satellites simultaneously for data transmission, tracking and spacecraft control via NASA’s communication network (NASCOM). The functions and characteristics of the White Sands ground terminal are presented.
    • TT & C SYSTEM FOR AT&T TELSTAR 3

      Moore, Joe S.; Ohlrogge, Larry D.; Hughes Aircraft Company (International Foundation for Telemetering, 1981-10)
      The first of three TELSTAR 3 satellites will be launched in mid 1983. Prior to this time, a Telemetry Tracking and Control system will have been installed to track and command the satellites during transfer orbit and will continue these tasks when each satellite is in it’s working orbit. This system consists of the Satellite Control Center (SCC) and the Primary Satellite Control Earth Station (PSCES), co-located at Hawley, Pennsylvania. In the event of unforeseen circumstances, the alternate satellite control center and earth station at Three Peaks, California, would be capable of performing the on-station Telemetry, Tracking, and Command operations for all three TELSTAR 3 satellites. Each location has redundant computer systems which are capable of all telemetry and command processing for three spacecraft. Only the Hawley site has the capability for tracking during transfer orbit by using the 13 meter full-motion antenna. This 13 meter antenna also houses the computercontrolled test equipment that will perform initial in-orbit testing of all three satellites, as well as normal testing throughout the life of the satellites. During transfer orbit, remote tracking station services will be provided by stations which are not part of the AT&T system. Data collected by the remote stations will then be sent to the SCC at Hawley for use in determining attitude and orbit. The second and third launches are scheduled for Mid 1984 and 1985, respectively.
    • TT&C COMMUNICATIONS ARCHITECTURE FOR THE NEXT GENERATION OF MILSATCOM SYSTEMS

      Wolfson, Charles R.; Defense Communications Agency (International Foundation for Telemetering, 1981-10)
      Military Satellite Communication (MILSATCOM) systems are developed and deployed to provide enduring communications for essential Department of Defense (DoD) missions (Reference 1-5). These missions must be completed under the direct influence of, and subsequent to, hostile electromagnetic and physical attacks. Additionally, mission and TT&C communications must be capable of propagating through a disturbed atmosphere (Ref 6). The classic tracking, telemetry and control (TT&C) functions provide critical support to all essential communications missions. Enduring TT&C is necessary for effective enduring MILSATCOM missions (Ref 7). The next generation of MILSATCOM systems includes many capabilities that can be shared by the mission traffic and TT&C communications to efficiently and effectively accomplish both objectives. This paper advocates an integration of TT&C into the communications channels for the next generation of MILSATCOM Systems.
    • 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.