• International Telemetering Conference Proceedings, Volume 18 (1982)

      International Foundation for Telemetering, 1982-09

      Robbins, Robert B.; Data Systems Division (International Foundation for Telemetering, 1982-09)
      The use of a Digital Equipment Corporation VAX computer under the VMS operating system, in a real-time telemetry environment, brings with it many advantages. These advantages pertain to its ability to handle real-time telemetry processing in an efficient and relatively straight forward manner. The author will use the TELSET, TELDAX and TELFOR telemetry software systems as the basis for demonstrating the techniques which have allowed the real-time telemetry user to take advantage of a 32-bit, virtual addressing, architecture.
    • Telemetering Standards Coordination Commitee

      Jennings, Vernon A. (International Foundation for Telemetering, 1982-09)

      Hahn, Jacob C.; Rockwell International M/S DA-37 (International Foundation for Telemetering, 1982-09)
      PCM data is recorded on magnetic tape on-board the Space Shuttle during flight. After the vehicle has landed these tapes are played back into a laboratory tape recorder and copies or dubs are made. PCM data from the vehicle is also recorded during manufacture and preflight testing and dubs of these tapes are made. Signals from other electronic equipment at the recording site can be picked up and mixed with the PCM data. This can cause dropouts (loss of data) during playback. The low frequencies are easily removed by filtering but higher frequencies that lie in the same range as the data cannot be removed by filtering. Methods for dealing with this problem have been worked out with some success. The work has just started. Some of the results are described here.

      Reber, Tilo F.; New Mexico State University (International Foundation for Telemetering, 1982-09)
      This paper concerns itself with the interface between men and computerized telemetry systems. This interface relates to the operation, planning, and implementation of setup and data processing functions. One of the major problems in operating a telemetry system is the programming of equipment parameters. This programming is often done by skilled “real-time” software personnel. This is both a costly and restrictive approach. The author has developed a “friendly” menu-driven, operator interactive, approach to solving these problems. The man-machine interface consists of software developed to present telemetry system options to an operator for selection. These options are displayed via the operator’s CRT. These displays are menus and they are formatted to display operator options in telemetry language. The object is to allow normal telemetry operators to configure the equipment setup and the data processing parameters. Once the configuration has been defined, the system can be configured quickly and precisely by the computer software. Changes to a setup or data processing configuration can be made by telemetry operators without the help of full-time programmers.

      Michaud, Colonel Normand; Hollander, Sidney; Hq Air Force Satellite Control Facility (AFSCF); The Aerospace Corporation (International Foundation for Telemetering, 1982-09)
      This paper updates the previous work,¹ which described the overall telemetry and data processing capabilities of the Data System Modernization (DSM) system being developed at the Air Force Satellite Control Facility (AFSCF). Having passed the System Critical Design Review milestone, the DSM program is proceeding with the design and implementation of various elements which support both the real-time routing, processing, storage, and display of satellite telemetry data, as well as the off-line recall of raw or processed telemetry data for trend analysis and satellite operations planning. A Data Distribution Element routes data received from 13 Remote Tracking Station (RTS) antennas and other sources to dedicated telemetry processing elements located within eight Satellite Test Center (STC) Mission Control Complexes (MCCs), a Range Control Complex (RCC), and the System Development and Test Laboratory (STDL). Two types of telemetry preprocessing elements are provided: one for processing telemetry data of rates less than 32 kilobits per second (or for processing selected measurands from telemetry data of rates up to 1.024 megabits per second), and the other for processing high-rate telemetry up to 5 megabits per second. Computer programs executing within one of two large mainframe computers and a Telemetry Contact Support Equipment Group in each MCC selectively decommutate, compress, calibrate, and store the telemetry data. Once processed, the data is formatted into unique, user-defined displays for real-time or post-contact analysis. Interfaces are also provided to satellite commanding routines for the authentication or verification of commands that have been transmitted to the satellite during the contact. Additional computer programs provide the capability to extract designated measurands from the processed telemetry history files, and format them, into messages for near realtime transmission to users remotely located from the STC. A capability is also provided to interface future telemetry preprocessing equipment, such as that required to support multiple scientific payloads aboard the Space Shuttle.

      Tinsley, Harold D.; SCI Systems, Inc. (International Foundation for Telemetering, 1982-09)
      The MX Instrumentation Multiplexer Set is used to acquire data during test flights of the MX Missile. The Multiplexer Set consists of a Multiplexer Programmer Controller Unit (MU), from 2 to 32 Remote Multiplexer Units (RU’s), and any number of Power Supply Verifier Units (PSV’S). The primary purpose of the MU is to operate as the programmable system controller, acquire local data inputs, and format this data along with data from the RU’s in a PCM Output. The RU’s interface to the MU via Instruction and Reply Data Buses providing remote data acquisition. The PSV’s provide an accurate stimulus voltage to the analog sources along with a control to offset the analog signal for test verification. Thirty-one of the possible 32 RU’s connect to the MU by two pairs of vehicle data buses, while the remaining RU is connected via the umbilical data bus. This ground resident RU is identical to the flight RU’s, but its functional requirement is quite different as it is primarily used to load and verify MU programs. Each of the vehicle data buses can be up to 130 feet in length with a 250 foot length allowed for the umbilical bus. An ideal terminated bus is not feasible in the MX application since the bus configuration changes as the missile stages. Staging will produce opens or shorts on the cable; to insure proper operation of all remaining RU’s on the bus, the interface isolation transformer incorporates both voltage and current windings to provide maximum secondary signal level with minimum reflection distortion. The data bus operates at 3.2 MHz using a Manchester II coded signal. The MU can sample 160 local differential analog channels that are programmable in gain, off-set, and to a maximum rate of 170,665 samples per second. A flexible grouping of 8 discrete inputs from the 96 discrete channels is programmable to a rate of 51,200 samples per second. The MU can also access data from four serial digital channels and provide outputs on eight command channels. During pre-flight the commands can be ground initiated, and following launch they can be time event programmed as well as being programmed repetitive in either mode. The PCM rate is 1.6 Mbps and the MU stores five in-flight selectable formats in a 4096 words by 16 bits CMOS RAM memory. Each RU can access 28 analog and 8 discrete channels, and the RU can control two command and six verification channels. The PSV does not interface to the data bus; it is controlled via a MU or RU command channel. The system can be externally synchronized or operated from an internal clock with a graceful transfer to eliminate data loss. Small size, light weight, low power and high reliability are primary characteristics of the system. Built-in monitors and fully automated computer controlled test equipment provide rapid and extreme parameter testing with a high degree of fault isolation.

      KNOX, K. D.; MALLETTE, L. A.; HUGHES AIRCRAFT COMPANY (International Foundation for Telemetering, 1982-09)
      This paper describes the signal routing and power combining function of the C-band uplink frequency signals in the Galaxy TT&C earth station.

      Willis, James; New Mexico State University (International Foundation for Telemetering, 1982-09)
      This paper deals with the use of preprocessors to reduce loading on real-time computers. The problem of multiplexing large amounts of data, exceeding the processing capabilities of most large-scale, real-time computers is discussed in detail. Implementation of hardware solutions to multiple Pulse Code Modulation (PCM) link multiplexing is dealt with. Use of firmware algorithms to reduce preprocessor front-end loading, as well as through-put reduction is discussed. The paper covers the different techniques used to take advantage of modern firmware preprocessor/multiplexers to select data for real-time computer processing.

      Solomon, Otis M., Jr.; Sandia National Laboratories (International Foundation for Telemetering, 1982-09)
      In this paper, the problem of non-constant tape speed is examined for frequency modulated signals. Frequency modulation and demodulation are briefly reviewed. Tape speed variation is modeled as a distortion of the independent variable of a frequency modulated signal. This distortion produces an additive amplitude error in the demodulated message which is comprised of two terms. Both depend on the derivative of time base error, which is the flutter of the analog tape machine. The first term depends on the channel’s center frequency and frequency deviation constant as well as flutter, while the second depends solely on the message and flutter. The relationship between the additive amplitude error and manufacturer’s flutter specification is described. Relative errors and signal-to-noise ratios are discussed for the case of a constant message to gain insight as to when tape speed variation will cause significant errors. An algorithm which theoretically achieves full compensation of tape speed variation is developed. The algorithm is confirmed via spectral computations on laboratory data. Finally, the algorithm is applied to field data. The reference is a temperature signal which is a non-zero constant, and the message is a pressure signal. The spectrum of the uncompensated message is clearly contaminated by the additive amplitude error, whereas the spectrum of the compensated message is not. Incorporation of this algorithm into the data-playback/data-reduction procedures is shown to greatly improve the measurement signal accuracy and quality. The treatment is nonmystical in that all derivations are directly tied to the fundamental equations describing frequency modulation and demodulation.

      Hedeman, Walter R., Jr. (International Foundation for Telemetering, 1982-09)
      The locus of recording when using IRIG standard bias methods is deduced from data on phase distortion presented by the author at ITC 1972. Contrary to popular opinion recording does not occur at the trailing edge of the record gap. At the maximum depth of recording it takes place near the center of the record gap, and in the surface layers next the record head approximately one half the record gap length past the trailing edge of the record gap.

      Endler, Harvey; Turner, William; Electra Magnetic Processes, Inc. (International Foundation for Telemetering, 1982-09)
      Novel RF circuitry for selecting the stronger of two telemetry signals (RHCP or LHCP) is presented. Polarization diversity capability with uninterrupted data flow can be achieved without using two expensive single channel data receivers and a diversity combiner. In certain dedicated systems only a single AM/FM receiver is required. This paper describes the RF signal processing and logic circuitry of a developed system and describes how it is applied in a lightweight polarization diversity single channel monopulse tracking system.

      Shingledecker, D. K.; Hughes Aircraft Company (International Foundation for Telemetering, 1982-09)
      The Space Shuttle Orbiter’s Ku-band integrated radar and communications subsystem will function in its radar role during satellite rendezvous. As a radar the Ku-band subsystem searches for, acquires, and then tracks targets. In the track mode, the radar outputs measured range, range-rate, angle, and angle-rate values to both the Orbiter’s general purpose computer (GPC) and the astronaut’s Ku-band subsystem control panel. This data is used to navigate the Orbiter to its satellite rendezvous. The radar is integrated with the Ku-band communications function and thus achieves reduction in weight and volume compared with separate subsystems for each function. This paper provides a user oriented description of the radar subsystem. Topics to be covered are radar requirements, modes of operation, and system configuration.

      Zelon, Michael; Space Transportation & Systems Group Rockwell International (International Foundation for Telemetering, 1982-09)
      The payload interrogator (PI) for communication between the orbiter and detached DOD/NASA payloads is described. Salient features of the PI are discussed, including its capabilities and limitations. For compatible operation in the orbiter’s electromagnetic environment, the PI is equipped with a dual triplexer assembly. A limiter diode circuitry allows the PI to be safely exposed to high effective isotropic radiated power (EIRP) payloads at close range. A dual conversion PM short-loop receiver has a sufficient dynamic range for undistorted reception of near and distant payload signals. The PI acquires signals from compatible transponders within ±112 kHz of its center frequency. The center frequency can be set at 125-kHz steps for the spaceflight tracking and data network (STDN), 370 kHz for the deep space network (DSN), and 5 MHz for the space satellite control facility (SCF). The PI has falselock- on protection capability to accommodate reliable acquisition of standard NASA and DOD payload transponders. The wideband phase detector demodulates baseband information, and by the use of AGC, provides three independent constant-level data outputs. Each of the 861 frequency channels is generated instantaneously by the receiver and transmitter synthesizers. The PM-modulated RF carrier transfers command information to the detached payloads. The RF output power is adjustable to assure reliable communication with payloads of various sensitivities (G/T). A wide and narrow carrier sweep capability is provided to accommodate any frequency uncertainty of payloads. The transmitter has an ON-OFF modulation control to avoid false-lock-on problems. The PSP command input modulation index is fixed, while the modulation index for the PS is a function of the input voltage. The PI receiver’s complementary transmit channels are spaced 115 kHz for STDN, 341 kHz for DSN, and 4 MHz for SCF. The PI is compatible with the orbiter’s configuration control equipment—GCIL, the PSP and PS for I/O data transfer, the Ku-band subsystem for “bent pipe” baseband telemetry transmission to ground, the MDM for the PI’s telemetry transfer, and the RHCP/LHCP antenna subsystem. Overall PI capabilities and limitations for communication with unique payloads are also presented.

      Udalov, Sergei; Huth, Gaylord K.; Batson, Bartus H.; Roberts, Donald; Axiomatix Corp.; NASA/Johnson Space Center (International Foundation for Telemetering, 1982-09)
      The anticipated requirements for Shuttle Orbiter Ku-band downlink communication include the transmission of a digital video signal which, in addition to accommodating the black-and-white TV pictures, must also be able to relay to the ground the color TV information encoded in either field-sequential or NTSC color formats. Furthermore, at the expense of additional onboard hardware and increased bandwidth due to the digitization process, the picture privacy feature can be provided for the downlink. Thus, an objective for the future Space Shuttle TV equipment is the development of a digitization technique which is not only compatible with data rates in the range of 20 -30 Mbps, but also provides good quality pictures. This paper desribes a tri-state delta modulation/demodulation (TSDM) technique which is a good compromise between implementation complexity and performance. The salient feature of TSDM is that it provides for efficient run-length encoding of constant-intensity segments of a TV picture. Axiomatix has developed a hardware implementation of a highspeed TSDM transmitter and receiver for black-and-white TV or field-sequential color or NTSC format color. The hardware aspects of this TSDM are discussed in the paper also.

      THOM, GARY A.; AYDIN MONITOR SYSTEMS (International Foundation for Telemetering, 1982-09)
      Today’s state of the art in semiconductor technology coupled with innovative computer architecture techniques can provide tomorrow’s telemetry industry with advanced ground station capabilities. Computer systems have traditionally been used to process all of the telemetry data. As data transmission speeds increase, the computer system can no longer handle real time processing so preprocessors are being used to handle the additional computational requirements. An alternative approach is to embed special purpose processors into applicable elements of the front-end equipment. These processors can be optimized for the function they are to perform, which prevents under utilization of processing power and enhances the flexibility and performance of the front-end element. These special purpose processors take up little real estate when implemented with todays LSI and VLSI semiconductors. The modules which are ideally suited for this type of technology are serial data correlators, decommutators, real time data correction, engineering units conversion, quick look display, data simulation and many special application modules. These processing elements provide the building blocks for a very powerful, cost effective family of modular telemetry and communications products for the 80’s and beyond.

      Harney, Paul F.; NASA Ames Research Center (International Foundation for Telemetering, 1982-09)
      The overall objective of the advanced fighter technology integration/F-16 (AFTI/F-16) advanced development program is to demonstrate, separately and in combination, advanced fighter technologies to improve air-to-air and air-to-surface weapon delivery and survivability. Real-time monitoring of aircraft operation during flight testing is necessary not only for safety considerations but also for rapid preliminary evaluation of flight test results. The complexity of the AFTI/F-16 aircraft requires an extensive capability to accomplish real-time data goals; this paper describes that capability and the resultant product.

      Baker, George; Martin Marietta Corporation (International Foundation for Telemetering, 1982-09)
      The quantity of measurements and broad frequency spectrum of interest for dynamic measurements required to support the development phase of the MX Missile, in conjunction with a limited downlink telemetry bandwidth, necessitated a unique vibration measurement system. This was accomplished by on-board vibration data processing comprising a sensor system (transducer/ low noise cable/charge amplifier) and a multichannel digital Vibration Data Processor (VDP). The processor is a 1/3 octave frequency band analyzer, employing digital filter circuitry covering 22 bands over a frequency range from 14 Hz to 2245 Hz, providing an output that represents the energy(G²) per band/time interval. A Master Data Control Unit (MU) controls the VDP operation via a full duplex data bus. This paper will describe the sensor system, with its designed in-post installation test/verification features and the capabilities and design features of the VDP. Processor characteristics such as the self-test operation whereby all 1/3 octave analysis bands are verified, the ability to meet a 60 dB dynamic range, the indivudual instructions code capability along with other features will be presented. The most important facet of this onboard processing allows a downlink data bandwidth conservation ranging up to 184:1 which is compatible with the digital telemetering system.

      Johnson, F. Bruce; Colorado Video, Inc. (International Foundation for Telemetering, 1982-09)
      This paper presents a method for synchronous conversion of infra -red image data to a Pulse-Code Modulation (PCM) bit stream for recording on instrumentation tape recorders. The PCM data recording method provides an improvement over analog FM recording in signal to noise ratio, horizontal resolution, and speed of data formatting. The methodology was applied to the design of a PCM encoder for an AGA model 680 Thermovision camera. The extension of the design to other devices is discussed. Considerations for the display of real-time and reduced speed data display on conventional television monitors are presented.

      Brown, Roger W.; McDonnell Douglas Astronautics Company (International Foundation for Telemetering, 1982-09)
      This paper will demonstrate a computer application program to predict the spectral shape and IRIG-RF bandwidth required for a PCM/FM telemetry system. A filtered PCM bit stream is constructed from a Fourier series and used to FM-modulate the RF carrier. The Fourier transform of the FM-wave is calculated numerically, and voltage amplitude levels are plotted on a Tektronix graphic display. Several PCM bit patterns are used and a composite display is formed to approximate an actual PCM/FM spectrum. A comparison of predicted and actual spectra will be presented.