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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,423 records · Page 79
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Tracking and orbit determination strategies for the AMPTE mission set

The three-spacecraft AMPTE mission set to be Delta-launched in August 1984 will become the first highly-elliptical Earth orbiters to be supported by the Deep Space Network. Orbit accuracies for the transponder-equipped CCE and IRM spacecraft are defined using coherent doppler and range, non-coherent doppler, and angles. Required navigation accuracies for both spacecraft are met using coherent doppler, and while the use of range enhances the achievable accuracy, it is not a required radio metric data type. Use of non-coherent doppler and angles shows that the IRM navigation accuracy requirements can also be met using listen-only antennas, although this requires an accurate estimate of the doppler bias.

Frauenholz, R. B.↗
NASA NTRS1982

Tidbinbilla two-element interferometer

A phase-stable two-element interferometer has been formed by linking the 64- and 34-m antennas of the Deep Space Network at Tidbinbilla, Australia. Utilizing the existing first-stage maser receivers at 2.3 GHz to yield a system temperature of approximately 20 K, the system has a 5 sigma detection sensitivity of 50 mJy in 1 s, with a rms confusion of approximately 6 mJy. The 195-m north-south baseline permits positional measurements to approximately 2 arcsec of sources stronger than approximately 100 mJy over the declination range -80 to +30 deg. Such measurements are ideally suited for the optical identification of weak radio sources. It is planned to extend the frequency of operation of the instrument to 8.4 GHz in the near future.

Batty, M. J.↗
NASA NTRS1982

Sensitive ammonia observations in the southern hemisphere

The 64-m spacecraft communication antenna of the NASA-JPL Deep Space Network has been equipped for spectral line observations at K band (18-25 GHz). To demonstrate the potential of this system, preliminary observations of the (1, 1) transition of ammonia are reported for a selection of eight southern molecular clouds. Estimates of gas density and ammonia column density are reported for six sources.

Dickinson, D. F.↗
NASA NTRS1982

Publications of the Jet Propulsion Laboratory, 1981

Over 500 externally distributed technical reports released during 1981 that resulted from scientific and engineering work performed, or managed by Jet Propulsion Laboratory are listed by primary author. Of the total number of entries, 311 are from the bimonthly Deep Space Network Progress Report, and its successor, the Telecommunications and Data Acquisition Progress Report.

Source record↗
NASA NTRS1982

Determination of intercontinental baselines and Earth orientation using VLBI

A series of experiments was conducted during the last decade to explore the capability of very long baseline interferometry (VLBI) to measure the crustal and rotational motions of the Earth with accuracies at the centimeter level. The observing stations are those of NASA's Deep Space Network in California, Spain and Australia. A multiparameter fit to the observed values of delay and delay rate yields radio source positions, polar motion, universal time, the precession constant, baseline vectors, and solid Earth tides. Source positions are obtained with formal errors of the order of 0''.01. UT1-UTC and polar motion are determined at 49 epochs, with formal error estimates for the more recent data of 0.5 msec for UT1-UTC and 2 to 6 mas for polar motion. Intercontinental baseline lengths are determined with formal errors of 5 to 10 cm. The Love numbers and Earth tide phase lag agree with the commonly accepted values.

Sovers, O. J.↗
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 NTRS1982

Viterbi decoder node synchronization losses in the Reed-Solomon/Veterbi concatenated channel

The Viterbi decoders currently used by the Deep Space Network (DSN) employ an algorithm for maintaining node synchronization that significantly degrades at bit signal-to-noise ratios (SNRs) of below 2.0 dB. In a recent report by the authors, it was shown that the telemetry receiving system, which uses a convolutionally encoded downlink, will suffer losses of 0.85 dB and 1.25 dB respectively at Voyager 2 Uranus and Neptune encounters. This report extends the results of that study to a concatenated (255,223) Reed-Solomon/(7, 1/2) convolutionally coded channel, by developing a new radio loss model for the concatenated channel. It is shown here that losses due to improper node synchronization of 0.57 dB at Uranus and 1.0 dB at Neptune can be expected if concatenated coding is used along with an array of one 64-meter and three 34-meter antennas.

Deutsch, L. J.↗
NASA NTRS1982

The fabrication and surface tolerance measurements of the JPL clear aperture microwave antenna

Present ground station microwave antennas of the Deep Space Network are of the symmetric dual reflector (cassegrainian) type. An investigation is being made of alternative high-performance offset antenna designs which have a clear aperture (no reflector or structural blockage) with shaped reflector surfaces. A 1.5-m, 32-GHz clear aperture model was built for experimental studies. The unique processes of fabrication, surface measurement, and alignment are described.

Carpenter, J.↗
NASA NTRS1982

Mark IVA microprocessor support

The requirements and plans for the maintenance support of microprocessor-based controllers in the Deep Space Network Mark IVA System are discussed. Additional new interfaces and 16-bit processors have introduced problems not present in the Mark III System. The need for continuous training of maintenance personnel to maintain a level of expertise consistent with the sophistication of the required tools is also emphasized.

Burford, A. L.↗
NASA NTRS1982

The 26-meter antenna s-x conversion project

Programmatic and management aspects of converting an existing 26-meter S-band subnet to a 34-meter S- and X-band subnet of the Deep Space Network are described. The stations involved were DSS 12 near Barstow, DSS 44 in Australia, and DSS 62 in Spain. The main subsystems affected by the conversion were the antenna mechanical, antenna microwave, and receiver-exciter. Antenna mechanial modifications and electronic additions and changes are described. The design and analysis of critical areas are considered and antenna performance is discussed.

Source record↗
NASA NTRS1983

Description and overview of an instrument designed to measure line-of-sight delay due to water vapor

Eight dual channel microwave radiometers were constructed as a research and development effort for the Crustal Dynamics Project and the Deep Space Network. These instruments, known as water vapor radiometers, are primarily intended to demonstrate that the variable path delay imposed by atmospheric water vapor can be calibrated in microwave tracking and distance measuring systems but could also be used in other applications involving moist air meteorology and propagation studies. They are being deployed to various stations and observatories that participate in Very Long Baseline Interferometry experiments. The development history of these instruments are reviewed, the theory of operation and overall design considerations are outlined, and the instrumental parameters and performance characteristics are described.

Resch, G. M.↗
NASA NTRS1983

Antenna arraying performance for deep space telecommunications systems

Antenna arraying is a crucial Deep Space Network technique in maximizing the science return of planetary and comet encounters. The equations which describe the total figure of merit for a multiple system of arrayed antennas are developed. An example is given for three Canberra DSN antennas and the Parkes 64-m antenna to be arrayed for the Voyager 2 Uranus flyby.

Stelzried, C. T.↗
NASA NTRS1983

The 1986 launch of the Galileo spacecraft via the Space Transportation System

Beginning with the Galileo spacecraft launch, deep space payloads will be launched via the Space Shuttle. This change from the previous use of expendable launch vehicles will introduce large changes in procedures and data flow configurations for both the flight project and the Deep Space Network during the launch period. The planned Galileo launch period sequence of events and telemetry and command data flow configurations are described.

Berman, A. L.↗
NASA NTRS1982

Telemetry system

The means of telemetering digital data from a spacecraft to the Deep Space Network is addressed. Phase shift keying and uncoded quadriphase shift keying modulations are discussed along with demodulation and decoding systems. Telemetry system losses and noisy reference performance for suppressed carrier receivers are also examined.

Yuen, J. H.↗
NASA NTRS1982

Spacecraft radio frequency subsystem

The historical background for the development of the planetary (RFS) is reviewed, and the performance capabilities of the various functional subassemblies are described. The flight radio frequency subsystem is a valid component for the three spacecraft telecommunications functions of tracking, command, and telemetry. It is the radio and the signal processing equipment residing in the spacecraft that interfaces with the control & data subsystem and performs two-way communications with the Earth-based Deep Space Network. The RFS consists of all the elements for RF reception, demodulation, modulation, and transmission, including those for command detection and telemetry modulation.

Tam, M. K.↗
NASA NTRS1983

The Telecommunications and Data Acquisition Report

Archival reports on developments in programs managed by JPL's office of Telecommunications and Data Acquisition (TDA) are presented. In space communications, radio navigation, radio science, and ground-based radio astronomy, it reports on activities of the Deep Space Network (DSN) and its associated Ground Communications Facility (GCF) in planning, in supporting research and technology, in implementation, and in operations.

E. C. Posner↗
NASA NTRS1983

Root Locus Algorithms for Programmable Pocket Calculators

Two algorithms are described which allow the plotting of individual points on a root locus diagram with or without time delay. The development was performed during the design of a continuous phase shifter used in the Baseband Antenna Combiner for the Deep Space Network (DSN). The algorithms, which are expected to be useful in similar DSN efforts, are simple enough to be implemented on a programmable pocket calculator. The coordinates of the open-loop zeros and poles, the gain constant K, and the time delay T are the data inputs.

Wechsler, E. R.↗