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NASA NTRS1976

Telemetry packetization for improved mission operations

The requirements for mission-operations data management will accelerate sharply when the Space Transportation System (i.e., Space Shuttle) becomes the primary vehicle for research from space. These demands can be satisfied most effectively by providing a higher-level source encoding function within the spaceborne vehicle. An Instrument Telemetry Packet (ITP) concept is described which represents an alternative to the conventional multiplexed telemetry frame approach for acquiring spaceborne instrument data. By providing excellent data-integrity protection at the source and a variable instrument bandwidth capability, this ITP concept represents a significant improvement over present data acquisition procedures. Realignments in the ground telemetry processing functions are described which are intended to take advantage of the ITP concept and to make the data management system more responsive to the scientific investigators.

Greene, E. P.↗

NASA NTRS1978

A packet telemetry system employing ARQ error control

A proposed packet telemetry system employing automatic retransmission request (ARQ) mode of error control is characterized. Limitations of the present multiplexing/demultiplexing approach are considered, and the use of the proposed system in near-earth satellites in the 1980s is suggested. Onboard processing and an adaptive multiplexing technique are described, as is an elastic buffer, required because the instantaneous data rate will be different from the telemetry transmission rate. The telemetry packets would be encoded into a powerful error-detection block code. A mechanism involving temporary buffering in a long shift register will permit retransmission request from the ground station for packets received in error. The ARQ mode of operation should ensure essentially error-free transmission at lower signal-to-noise ratios and at considerably higher transmission rates than are usually used.

Greene, E. P.↗

NASA NTRS1977

In-vivo bone strain telemetry in monkeys /M. nemestrina/

A new method for collecting in-vivo bone strain data in monkeys has been developed and tested. The method includes a system which consists of a new design of implantable strain transducer and its companion telemetry package. The transducer fits into a hole drilled in a monkey tibia and is threaded for subsequent bone ingrowth. The transducers and telemetry package are biocompatible for over 503 days. The telemetry package uses Pulse Interval Ratio Modulation (PIRM) to transmit strain information to receiving equipment located outside the animal housing cage.

Young, D. R.↗

NASA NTRS1979

Single frequency RF powered ECG telemetry system

It has been demonstrated that a radio frequency magnetic field can be used to power implanted electronic circuitry for short range telemetry to replace batteries. A substantial reduction in implanted volume can be achieved by using only one RF tank circuit for receiving the RF power and transmitting the telemetered information. A single channel telemetry system of this type, using time sharing techniques, was developed and employed to transmit the ECG signal from Rhesus monkeys in primate chairs. The signal from the implant is received during the period when the RF powering radiation is interrupted. The ECG signal is carried by 20-microsec pulse position modulated pulses, referred to the trailing edge of the RF powering pulse. Satisfactory results have been obtained with this single frequency system. The concept and the design presented may be useful for short-range long-term implant telemetry systems.

Ko, W. H.↗

NASA NTRS1981

Mark 4-A DSCC telemetry system description

This system is designed as a replacement for the Mark III. Two major changes in the DSCC portion of the DSN Telemetry System are discussed: the addition of two 34 meter antennas to each DSCC; and the configuration of the telemetry system. The telemetry system is configured to support either two deep space missions and one highly elliptical orbit, or two highly elliptical orbits and one deep space mission.

Burt, R.↗

NASA NTRS1981

The effect of noisy carrier reference on telemetry with baseband arraying

Imperfect carrier reference causes a degradation in detection performance in coherent communication systems. A measure of this degradation is the radio loss, which is the amount of increase in data signal to noise ratio (SNR) per bit required to achieve the same bit error rate when carrier reference is perfect. Performance analysis and numerical results are obtained for the Voyager high rate telemetry link with maximum likelihood convolutional decoding. The arraying of antennas provides not only improved performance due to an increase in effective antenna aperture, but also a decrease in radio loss with respect to a single antenna. This telemetry link performance improvement is a function of the carrier loop SNR and data bit error rate. When the carrier loop SNR's are low, it provides a significant improvement in the telemetry link performance since the decrease in radio loss with respect to a single station is substantial.

Divsalar, D.↗

NASA NTRS1980

Telemetry Computer System at Wallops Flight Center

This paper describes the Telemetry Computer System in operation at NASA's Wallops Flight Center for real-time or off-line processing, storage, and display of telemetry data from rockets and aircraft. The system accepts one or two PCM data streams and one FM multiplex, converting each type of data into computer format and merging time-of-day information. A data compressor merges the active streams, and removes redundant data if desired. Dual minicomputers process data for display, while storing information on computer tape for further processing. Real-time displays are located at the station, at the rocket launch control center, and in the aircraft control tower. The system is set up and run by standard telemetry software under control of engineers and technicians. Expansion capability is built into the system to take care of possible future requirements.

Bell, H.↗

NASA NTRS1982

The performance of VLA as a telemetry receiver for Voyager planetary encounters

The Very Large Array (VLA) was proposed for use as a supplement to the Deep Space Network (DSN) for telemetry reception at Voyager 2 Uranus and Neptune encounters. The main problem with the use of VLA for telemetry is that it is not capable of producing a continuous stream of data. Gaps of one millisecond follow every 51 milliseconds of data. The effect of these millisecond gaps on coded telemetry is investigated. An upgapped system of the same aperture as the VLA would be capable of handling data rates of 38.4 kbps at Uranus encounter and 19.2 kbps at Neptune encounter. It is shown that VLA with (7, 1/2) convolutional coding (the baseline coding scheme for Voyager) will support a data rate of 10.8 kbps but not 19.2 kbps at both Uranus and Neptune. It is also shown that by implementing Voyager's concatenated Reed-Solomon/convolutional coding capability, data rates of 38.4 kbps and 19.2 kbps would be achievable at Uranus and Neptune respectively. Concatenation also offers a factor of 2 improvement in overall throughput.

Deutsch, L. J.↗

NASA NTRS1984

Availability of the DSN Telemetry Data System and Its Major Elements, Including the TWM Assemblies

The DSN discrepancy report system which records all outages of DSN data systems that occur during mission support operations is described. The recorded outages of the telemetry data system for 1981 through 1983 were tabulated and availability characteristics of the telemetry data system and several of its major elements, including the traveling wave maser (TWM) Assemblies were developed. Availability characteristics of the TWM assemblies are compared with those of other DSN subsystems and assemblies. It is found that for a three year period, the availability of the telemetry data system is 99.0%, and its mean time to restore service is 0.9 hours; the availability of the TWM assemblies is 99.83%, and their mean time to restore service is 2.5 hours.

Stevens, R.↗

NASA NTRS1985

Miniature infrared data acquisition and telemetry system

The Miniature Infrared Data Acquisition and Telemetry (MIRDAT) Phase 1 study was performed to determine the technical and commercial feasibility of producing a miniaturized electro-optical telemetry system. This system acquires and transmits experimental data from aircraft scale models for realtime monitoring in wind tunnels. During the Phase 1 study, miniature prototype MIRDAT telemetry devices were constructed, successfully tested in the laboratory and delivered to the user for wind tunnel testing. A search was conducted for commercially available components and advanced hybrid techniques to further miniaturize the system during Phase 2 development. A design specification was generated from laboratory testing, user requirements and discussions with component manufacturers. Finally, a preliminary design of the proposed MIRDAT system was documented for Phase 2 development.

Stokes, J. H.↗

NASA NTRS1986

ICE telemetry performance

Acquiring telemetry data from the International Cometary Explorer (ICE) at its encounter with the comet Giacobini-Zinner on September 11, 1985 proved to be among the more difficult challenges the DSN has met in recent years. The ICE spacecraft began its life as an Earth orbiting monitor of the Solar Wind. At the comet, ICE was nearly 50 times as distant as in its initial role, with its signal strength diminished nearly 2500 times. Collecting enough of that weak signal to provide meaningful scientific data about the comet required unique new telemetry capabilities and special handling by the DSN. This article describes the development and validation of the DSN telemetry capability for ICE from its early planning stages through the successful comet encounter.

Layland, J. W.↗

NASA NTRS1987

Models of weather effects on noise temperature and attenuation for Ka- and X-band telemetry performance analysis

Models that show the effects of weather on noise temperature and attenuation of deep space telemetry signals received by the Deep Space Network (DSN) at Ka- and X-band (32 and 8.5 GHz) are developed. These models were used to compare the performance of telemetry links at these two frequencies. The models build on an earlier 1982 model that used three months of water vapor radiometer measurements (31.4 GHz) at Goldstone, augmented with one year of radiosonde measurements made at Edwards Air Force Base. This 1986 model accounts for annual variations of rainfall and extends to a model for Canberra, Australia, and Madrid, Spain. The results show, for example, that at Ka-band, 30 degrees elevation angle, Goldstone weather adds less than 23 + or - 2 K to the system temperature 80% of the time, while Canberra or Madrid weather adds less than 32 + or - 5 K 80% of the time. At X-band, the comparable numbers are 5.1 + or - 0.2 K and 5.7 + or - 0.4 K. A simple analysis shows a substantial telemetry system signal-to-noise ratio advantage when operating at Ka-band compared to X-band.

Slobin, S. D.↗

NASA NTRS1987

Trends in Space Station telemetry applications

Spacecraft telemetry systems have evolved from simple hardware devices to complex computer applications performing data acquisition and formatting tasks. This paper reviews the role of spacecraft computers in performing telemetry functions and examines computer-based telemetry systems being considered for use on the NASA Space Station.

Muratore, John F.↗

NASA NTRS1987

Telemetry handling on the Space Station data management system

This paper examines the impact of telemetry handling on the design of the onboard networks that are part of the Space Station Data Management System (DMS). An architectural approach to satisfying the DMS requirement for support of the high throughput needed for telemetry transport and for servicing distributed computer systems is discussed. Several of the functionality vs. performance tradeoffs that must be made in developing an optimized mechanism for handling telemetry data in the DMS are considered.

Whitelaw, Virginia A.↗

NASA NTRS1988

Flight and ground packet telemetry systems activities at NASA's Goddard Space Flight Center

NASA's Goddard Space Flight Center (GSFC) has the responsibility for the telemetry ground data processing for two current spacecraft which use packet telemetry. These spacecraft are the Hubble Space Telescope (HST) and the Gamma Ray Observatory (GRO). GSFC has designed and built two ground systems to meet this responsibility. The first is the HST DATA Capture Facility (DCF), which has now completed its integration and test phase and is supporting spacecraft and data flow tests. The second is the Packet Processor System (Pacor). This system became operational in July 1987. These systems are known generally as Level Zero Processors. Level Zero Processors ingest telemetry composite bit streams, output selected user specific data in real time, and in a batch mode perform all necessary processing to produce individual user data files which are, within the limits of the quality of the received data, contiguous, complete, ordered and nonredundant.

Carper, Richard D.↗

NASA NTRS1990

Mark 4-A DSCC (Magellan-era) telemetry system description

An update to the description of the Deep Space Communications Complex portion of the Mark 4-A Telemetry system is given. This system is currently implemented at all signal processing centers. The upgrade of the telemetry system was undertaken primarily in support of the Voyager-Neptune Encounter and the Magellan mission. The Mark 3 Telemetry System is the predecessor of the Mark 4-A system.

Ross, D. L.↗

NASA NTRS1991

System Decommutes And Displays Telemetry Data

TDPlus computer program software system for decommutation of pulse-code-modulation (PCM) telemetry signals. Provides synchronization, conversion into engineering units, and display of serial bit streams. Transforms IBM PC-compatible computer into PCM-telemetry-decommutation system. Synchronizes telemetric signals data and enables conversion back into such meaningful forms as voltage, current, pressure, and the like. Also controls operation of digital-to-analog converters to ship data to paper strip charts or to parallel digital ports for offloading to other computers. Software used to process actual data only when telemetry-data-processing computer modified in accordance with specifications contained in "TDPlus TM Data Processor" (GSC-13291). Written in Turbo C and 8088 Assembly language.

Massey, D. E.↗

NASA NTRS1990

The impact of NRZ data asymmetry on the performance of a space telemetry system

The telemetry data asymmetry due to rising and falling voltage transitions can cause undesired spectral components at the output of a spacecraft transmitter. The performance of a space telemetry system can potentially degrade because of these undesired components. Here, an expression is derived for the power spectral density of an asymmetric nonreturn-to-zero (NRZ) data stream. This formula is then used to investigate how the data bandwidth varies with data asymmetry. At the receiver end, the threshold levels of undesired spectral components that fall into the carrier-tracking-loop bandwidth are determined by examining the derived spectral density. Further, based on this formula, a simple technique is developed for the computation of bit signal-to-noise ratio (SNR) degradation due to data asymmetry. The telemetry bit SNR degradations derived using this technique are compared with results obtained previously and with measurements by the Electronic Systems Test Laboratory (ESTL) at the Lyndon B. Johnson Space Center.

Nguyen, T. M.↗