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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

The Telecommunications and Data Acquisition Progress Report 42-77

Activities in space communication, radio navigation, radio science, and ground-based astronomy are reported. Advanced systems for the Deep Space Network and its Ground-Communications Facility are discussed including station control and system technology. Network sustaining as well as data and information systems are covered. Studies of geodynamics, investigations of the microwave spectrum, and the search for extraterrestrial intelligence are reported.

Posner, E. C.↗
NASA NTRS1984

Satellite Emission Range Inferred Earth Survey (SERIES) project

The Global Positioning System (GPS) was developed by the Department of Defense primarily for navigation use by the United States Armed Forces. The system will consist of a constellation of 18 operational Navigation Satellite Timing and Ranging (NAVSTAR) satellites by the late 1980's. During the last four years, the Satellite Emission Range Inferred Earth Surveying (SERIES) team at the Jet Propulsion Laboratory (JPL) has developed a novel receiver which is the heart of the SERIES geodetic system designed to use signals broadcast from the GPS. This receiver does not require knowledge of the exact code sequence being transmitted. In addition, when two SERIES receivers are used differentially to determine a baseline, few cm accuracies can be obtained. The initial engineering test phase has been completed for the SERIES Project. Baseline lengths, ranging from 150 meters to 171 kilometers, have been measured with 0.3 cm to 7 cm accuracies. This technology, which is sponsored by the NASA Geodynamics Program, has been developed at JPL to meet the challenge for high precision, cost-effective geodesy, and to complement the mobile Very Long Baseline Interferometry (VLBI) system for Earth surveying.

Buennagel, L. A.↗
NASA NTRS1984

Update: San Andreas Fault experiment

Satellite laser ranging techniques are used to monitor the broad motion of the tectonic plates comprising the San Andreas Fault System. The San Andreas Fault Experiment, (SAFE), has progressed through the upgrades made to laser system hardware and an improvement in the modeling capabilities of the spaceborne laser targets. Of special note is the launch of the Laser Geodynamic Satellite, LAGEOS spacecraft, NASA's only completely dedicated laser satellite in 1976. The results of plate motion projected into this 896 km measured line over the past eleven years are summarized and intercompared.

Christodoulidis, D. C.↗
NASA NTRS1984

SEASAT observations of lithospheric flexure

Models of lithospheric flexure were tested on SEASAT altimetric observations of the geoid over Outer Rises. These altimeter data were found to provide significant new information about the strength of the oceanic lithosphere. Among the significant results derived from altimeter data is confirmation of the proposition that the effective elastic thickness, T sub e, of the lithosphere increases with age in approximate accord with the relation T sub E approximately equals C times one half the age. SEASAT altimeter data over Outer Rises provide an important constraint on mechanical models of the oceanic lithosphere. These data are quite consistent with an experimentally predicted mechanical model of the lithosphere which indicates that this model may be useful in other geodynamic investigations.

Mcadoo, D. C.↗
NASA NTRS1984

Recommended Program Activities, 1988-1998

The observations needed from the standpoint of measurement programs are considered and the technologies which must be developed and the flight missions which must be carried out to support ground-based measurements are discussed. Instrument development for millimeter accuracy in both the horizontal and vertical components as well as for sensitivity to short wavelengths is discussed. Algorithms and models in the application of space data in geodynamics demand special attention. Continued development of airborne and spaceborne laser ranging systems should be supported.

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NASA NTRS1984

Elimination of clock errors in a GPD based tracking system

This paper discusses the estimation problem for a GPS based tracking system which is used for low earth satellite orbit determination and for geodynamic research. The clock errors involved in the measurements are eliminated in order to obtain a solution. Two methods used to eliminate the clock errors, the double differencing method and the linear combination method are discussed and compared. The accuracy of the solution, the redundancy and the correlation of the differenced or the combined data are investigated. Numerical results of the two methods are presented.

Wu, J.-T.↗
NASA NTRS1985

Summary Presentation of the Science Applications Panel

The advantages of tethering several satellites are discussed. Future science TSS applications are enumerated, including planetary missions that involve getting payloads as close to a planetary surface as possible. Areas of scientific interest relating to tethered systems are listed: geodynamics, aeronomy, electrodynamics, and Earth observations.

Hudson, R.↗
NASA NTRS1985

Space Science and Applications

The exploitation of the present tethered system and the need for repeat missions; multiple payloads placed along the tether; the extension of the present altitude limit to below 130 km; the development of free-flying tether satellites for studying both the Earth's atmosphere and ionosphere and also for studying the plantes; and a subtether were discussed. Areas of research were identified: aeronomy studies, gravity and magnetic potential mission, advanced sensors for geodynamics, and mapping and remote sensing.

Hudson, R.↗
NASA NTRS1985

Crustal dynamics studies in China

Geodynamics of Mainland China and Taiwan are discussed. The following research was performed: (1) the tectonics along the Tanlu fault in eastern China; (2) tectonics in the Taiwan Strait behind the collision zone in Taiwan; and (3) analysis of faulting in the vicinity of the Altyn Tagn fault. It is found that the existence of the fault is traced back to at least Jurassic with the deposition of conglomerate sandstones in the troungh along the present Tanlu fault branches in the Shantung Province. Taiwan is the product of collision between the Phillipine plate and the Asian plate and Taiwan came into being because of a former island arc.

Wu, F. T.↗
NASA NTRS1985

A new instrument for the determination of radio path delay due to atmospheric water vapor

A new water-vapor radiometer is being developed to determine atmospheric path-delay corrections for geodynamics applications. The radiometer has microwave channels at 20.7, 22.2, and 31.4 GHz, and includes new features which should promote radiometric precision while at the same time reduce instrument complexity. The instrument will be compact, portable, and will possess a self-diagnostic capability to ensure reliability. The performance objective is the determination of the line-of-sight path delay through the atmosphere due to water vapor with a one-sigma error less than 0.5 cm at the zenith.

Janssen, M. A.↗
NASA NTRS1985

The Telecommunications and Data Acquisition Report

Deep Space Network (DSN) progress in flight project support, tracking and data acquisition research and technology, network engineering, hardware and software implementation, and operation is discussed. In addition, developments in Earth-based radio technology as applied to geodynamics, astrophysics and the radio search for extraterrestrial intelligence are reported.

Posner, E. C.↗
NASA NTRS1986

The Telecommunications and Data Acquisition Report

Deep Space Network progress in flight project support, tracking and data acquisition research and technology, network engineering, hardware and software implementation, and operations is documented. In addition, developments in Earth-based radio technology as applied to geodynamics, astrophysics and the radio search for extraterrestrial intelligence are reported.

Posner, E. C.↗
NASA NTRS1986

The Telecommunications and Data Acquisition Report

This publication, one of a series formerly titled The Deep Space Network (DSN) Progress Report, documents DSN progress in flight project support, tracking and data acquisition research and technology, network engineering, hardware and software implementation, and operations. In addition, developments in Earth-based radio technology as applied to geodynamics, astrophysics, and the radio search for extraterrestrial intelligence are reported.

Posner, E. C.↗
NASA NTRS1985

A comparison between Lageos laser ranging and very long baseline interferometry determined baseline lengths

NASA's Crustal Dynamics Project (CDP) has the objective to improve the understanding of geodynamics by measuring crustal deformation, tectonic motion, and polar motion and earth rotation. Three different approaches are utilized for obtaining these measurements. One is based on satellite laser ranging (SLR), while another makes use of very long baseline interferometry (VLBI) which uses reception of radio signals from quasars. The third approach involves laser ranging to the moon. An important part of the CDP is to compare baselines periodically or the straight-line distance between two points on the earth's surface as determined by either SLR or VLBI. Attention is given to the SLR analysis, the VLBI analysis, a local survey, and error sources. A table is presented with the baselines between SLR survey markers as measured by VLBI and SLR.

Kolenkiewicz, R.↗
NASA NTRS1985

Viscosity profile of the lower mantle

The viscosity of the earth's mantle is an important factor in studies of mantle convection and other problems in geodynamics. The present investigation is concerned with a determination of the variation of effective viscosity across the lower mantle from models of the Gibb's free energy of activation G(asterisk) and the adiabatic temperature profile. The variation of G(asterisk) with depth is calculated using both an elastic strain energy model, in which G(asterisk) is related to the seismic velocities, and a model which assumes G(asterisk) is proportional to the melting temperature.

Ellsworth, K.↗
NASA NTRS1985

Satellite laser ranging and its applications

Satellite laser ranging (SLR) provides an important capability for precise orbit determination and for geophysical parameter estimation to support a number of contemporary geodynamic and oceanographic investigations. The precision of the SLR measurement has improved from the early meter-level systems to the current capabilities of a few centimeters for the best systems. The accuracy of the orbits and geophysical parameter recovery have shown an associated improvement. Polar motion with accuracies of 2 mas, station coordinates better than 10 cm, and interstation baseline rates indicative of tectonic motion are determined routinely with the current set of global SLR data. This discussion reviews the SLR measurement, analysis approach, and some of the recent results derived from the current SLR data set.

Tapley, B. D.↗
NASA NTRS1986

The Telecommunications and Data Acquisition Report

This publication, one of a series formerly titled The Deep Space Network Progress Report, documents DSN progress in flight project support, tracking and data acquisition research and technology, network engineering, hardware and software implementation, and operations. In addition, developments in Earth-based radio technology as applied to geodynamics, astrophysics and the radio search for extraterrestrial intelligence are reported.

Posner, E. C.↗
NASA NTRS1986

Activities of the Jet Propulsion Laboratory

Work accomplished by the Jet Propulsion Laboratory (JPL) under contract to NASA in 1985 is described. The work took place in the areas of flight projects, space science, geodynamics, materials science, advanced technology, defense and civil programs, telecommunications systems, and institutional activities.

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