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NASA NTRS1983

New Directions: 1982-2000

The major objective of the Deep Space Network in the period 1983-2000 is the fulfillment of the extremely diverse telecommunications requirements of the known and anticipated users. Deep space exploration projects will continue to occupy a dominant role, although in the mid-1980s, with the completion of the Networks Consolidation Program, high Earth orbiter projects will become substantial users of the Network. Also playing an increasingly important role in the Network of the next decade will be non-flight projects, such as Geodynamics, Radio Astronomy, Radar Astronomy, and the Search for Extraterrestrial Intelligence (SETI). The major challenge in meeting the primary Network objective of the next decade will be that of providing increased performance as required by users at costs which can be borne by NASA in an environment of limited resources. Emphasis will be on increased commonality, flexibility, and automation to reduce maintenance and operations costs, and lower mission costs.

Renzetti, N. A.↗

NASA NTRS1983

The role of satellite laser ranging through the 1990's

Contributions of Satellite Laser Ranging (SLR) in the fields of geodesy, oceanography, geodynamics, and geopotential are reviewed. With the best current systems SLR has successfully defined an absolute vertical datum to 3 cm and a relative horizontal datum with comparable accuracy. In the areas of Earth and space physics SLR has demonstrated its ability to provide information regarding the vertical and horizontal movements of the lithosphere, the rheology of the Earth, improved understanding of the evolution of the Earth-Moon system, the Earth's albedo and upper atmosphere, the polar wander, the frequency structure of the polar motion and in the definition of fundamental constants. Future options are discussed. It is indicated that SLR will continue to provide a unique and powerful tool for the study of space and geosciences.

Christodoulidis, D. C.↗

NASA NTRS1982

1982 International Geoscience and Remote Sensing Symposium, Munich, West Germany, June 1-4, 1982, Digest. Volumes 1 & 2

Theoretical and experimental data which have defined and/or extended the effectiveness of remote sensing operations are explored, with consideration given to both scientific and commercial activities. The remote sensing of soil moisture, the sea surface, and oil slicks is discussed, as are programs using satellites for studying geodynamics and geodesy, currents and waves, and coastal zones. NASA, Canadian, and Japanese radar and microwave passive and active systems are described, together with algorithms and techniques for image processing and classification. The SAR-580 project is outlined, and attention is devoted to satellite applications in investigations of the structure of the atmosphere, agriculture and land use, and geology. Design and performance features of various optical scanner, radar, and multispectral data processing systems and procedures are detailed.

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NASA NTRS1983

The Telecommunications and Data Acquisition Report

Developments in programs in telecommunication and data acquisition in space communications, radio navigation, radio science, and ground based radio astronomy are reported. Activities of the deep space network (DSN) and its associated ground communication facility (GCF) in planning, supporting research and technology, implementation, and in operations are outlined. The publication of reports on the application of radio interferometry at microwave frequencies for geodynamic measurements are presented. Implementation and operation for searching the microwave spectrum is reported.

Posner, E. C.↗

NASA NTRS1982

Reference coordinate systems for Earth dynamics: A preview

Geodynamics is the subject of intensive international research during last decade. A common requirement for all investigations is the necessity of a well defined coordinate system attached to the Earth in some prescribed way. In addition, a well defined inertial coordinate system is also needed in which the motions of the terrestrial system can be monitored. The problems encountered when establishing such coordinate systems and the transformations between them are presented. In addition, problems related to the modeling of the deformable Earth are discussed. Finally, action items are listed which are necessary to assure that the reference system issue is resolved early and that uniformity is assured by means of international agreements.

Mueller, I. I.↗

NASA NTRS1980

The construction of a highly transportable laser ranging station

The technology of the transportable Laser Ranging Station (TLRS) used in crustal dynamics studies was examined. The TLRS used a single photoelectron beam of limited energy density returned from the Laser Geodynamic Satellite (LAGEOS). Calibration was accomplished by the diversion of a small portion of the outgoing beam attenuated to the same level as the satellite return. Timing for the system was based on a self calibrating Ortec TD811, 100 picosec time interval device. The system was contained in a modified, single chassis recreational vehicle that allowed rapid deployment. The TLRS system was only airmobile on the largest transport aircraft. A 30 cm simple plano/concave transfer lens telescope aided in beam direction. The TLRS system fulfills the need for an accurate method of obtaining range measurements to the LAGEOS satellite incorporated in a mobile, air transportable, and economical configuration.

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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.↗