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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

An estimate of the geodetic accuracy attainable with a transportable lunar laser station

A transportable lunar laser ranging station can be expected to measure the range to the lunar corner retroreflectors from a site on the earth's surface with an uncertainty of about 3 cm. The accuracy with which that station can infer its geocentric position is influenced by many factors including the uncertainties in the pole position and rotation rate of the earth and the data loss due to weather. The results of a simplified modeling study intended to include these factors are presented in cartographic form. The modeling indicates that, assuming the successful operation of three or more widely separated fixed laser stations, the transportable station will be able to determine its relative geocentric position in all three coordinates with an accuracy comparable to the original range uncertainty.

Silverberg, E. C.↗
NASA NTRS1977

Geodetic linear estimation technique and the norm choice problem

In this work the mathematical and probabilistic background of standard linear estimation techniques used in geodesy is clarified, and their interrelationship is revealed with the help of best approximation theory and the normal equations. Emphasis is given to the separation of the deterministic solution to the approximation problem from the probabilistic justification of the metric of the approximation. Least squares prediction has been related to deterministic (exact) collocation, and minimum error bound has been identified as a prediction optimality criterion in the latter. Criteria for the optimal choice of norm in Hilbert space collocation are proposed for gravimetric geodesy problems.

Dermanis, A.↗
NASA NTRS1977

National geodetic satellite program, part 1

The Applied Physics Laboratory (APL) space research program was directed toward modeling the gravitational field of the earth from an analysis of the Doppler shifts on the transmitted frequencies of the satellites as obtained by the tracking stations. Emphasis is on the satellites involved and the methods used in accomplishing this aim.

Dunnell, C. A.↗
NASA NTRS1977

National geodetic satellite program, part 1

Determinations of tracking station locations and the gravitational constant of the earth, based on Doppler-tracking data from lunar and planetary spacecraft are presented. Two-way Doppler data obtained by the Deep Space Network of the Jet Propulsion Laboratory (JPL) were used. The Deep Space Station instrumentation that JPL employed is described. How the stations were located is detailed, and the data used are discussed. Results are given together with an analysis of the errors.

Esposito, P. B.↗
NASA NTRS1977

National geodetic satellite program, part 1

The major accomplishments of the GEOS-B, C-band systems project is assessed. The project objectives are given, namely: (1) primary objectives that must be met for project success; (2) secondary objectives that were sufficiently important to warrant serious consideration; and (3) other objectives that were important to the project and for which additional effort would be desirable. The primary objectives are presented and discussed in detail.

Belgin, J.↗
NASA NTRS1977

National Geodetic Satellite Program, Part II: University of California, Los Angeles

Satellite orbit analyses are presented which were undertaken for: (1) reasons of insight and economy; (2) obtaining geophysically interesting tesseral harmonics; (3) comparing effects of tracking station location error drag, radiation pressure, and luni-solar attraction to tesseral harmonic effects; and (4) combination of satellite and terrestrial data. The analyses were divided into the following phases: (1) MINITRACK interferometry; early Baker-Nunn camera directions; (2) late Baker-Nunn camera directions; and (3) combined Baker-Nunn camera and TRANET Doppler data.

Kaula, W. M.↗
NASA NTRS1978

On the unification of geodetic leveling datums using satellite altimetry

Techniques are described for determining the height of Mean Sea Level (MSL) at coastal sites from satellite altimetry. Such information is of value in the adjustment of continental leveling networks. Numerical results are obtained from the 1977 GEOS-3 altimetry data bank at Goddard Space Flight Center using the Bermuda calibration of the altimeter. Estimates are made of the heights of MSL at the leveling datums for Australia and a hypothetical Galveston datum for central North America. The results obtained are in reasonable agreement with oceanographic estimates obtained by extrapolation. It is concluded that all gravity data in the Australian bank AUSGAD 76 and in the Rapp data file for central North America refer to the GEOS-3 altimeter geoid for 1976.0 with uncertainties which do not exceed + or - 0.1 mGal.

Mather, R. S.↗
NASA NTRS1978

Geodetic measurements at sea floor spreading centers

A network of 8 or more precision transponder units mounted on the sea floor and interrogated periodically from an instrument package towed near bottom through the area to provide the necessary spatial averaging could provide a practical system for observing the pattern of buildup of strain at intermediate and fast spreading centers.

Spiess, F. N.↗
NASA NTRS1978

Multibaseline - A precision ground based geodetic measurement technique

The multibaseline geometric measurement system and its capabilities are described. Station inplane coordinates can always be determined to subcentimeter accuracy by use of one- or two-color geodolites as the fundamental measuring devices; for a given station constellation only one station needs to be substantially out of the plane in order to permit determination of the remaining near inplane coordinates. A realistic simulation of the Palmdale, California geodimeter network is presented, and the equivalence between a static multilateration system and the multibaseline system is established. The extension of local networks to wider monitoring grids is considered.

Escobal, P. R.↗
NASA NTRS1979

Satellite emission radio interferometric earth surveying series - GPS geodetic system

A concept called SERIES (satellite emissions radio interferometric earth surveying) which makes use of GPS (global positioning system) radio transmissions without any satellite modifications, is described. Through the use of very long baseline interferometry (VLBI) and its calibration methods, 0.5 to 3 cm three dimensional baseline accuracy can be achieved over distances of 2 to 200 km respectively, with only 2 hours of on-site data acquisition. Attention is given to such areas as: the radio flux equivalent of GPS transmissions, synthesized delay precision, transmission and frequency subsystem requirements, tropospheric and ionospheric errors. Applications covered include geodesy and seismic tectonics.

Macdoran, P. F.↗
NASA NTRS1980

Geodetic long baseline interferometry research in Canada

The objectives and results of several studies using the Canadian long baseline interferometry system (LBI) are presented. The precision of measurements from radio telescopes at the Algonquin Radio Observatory (ARO), Lake Traverse, Ontario; the Owens Valley Radio Observatory (OVRO), Big Pine, California; and the Chilbolton Observatory (CHIL), Chilbolton, England, is discussed. Also, since LBI is insensitive to the uncertainty in the geocentric gravitational constant, it is a very useful technique for determining the scales of the coordinate systems used by other precise techniques. Beginning in May 1977, a number of LBI observing sessions were accompanied by simultaneous satellite Doppler observations. The baseline components obtained from the satellite Doppler observations were compared to the LBI values. The weighted mean scale bias of the NSWC 9Z-2 satellite Doppler coordinate system relative to the LBI system was found to be 0.42 + or - 0.05 PPM. The weighted mean difference in the origin of longitude was found to be 0.87 sec + or - 0.01 while the difference in declination origin was found to be 0.06 sec + or - 0.01.

Langley, R. B.↗
NASA NTRS1980

Phase versus delay in geodetic VLBI

The conditions for the applicability of the phase observable in very long baseline interferometry are discussed and examples of adequate observation programs are given. These considerations apply in particular to the Mark 2 system, which is already in operation at many observatories.

Campbell, J.↗
NASA NTRS1980

Phase delay astrometry and its geodetic applications

The accuracy inherent in the fringe phase in the determination of source positions was calculated. It is shown that accuracy can be utilized by applying differencing techniques in order to circumvent such systematic effects as clock drift and delay due to the propagation media.

Wittels, J. J.↗
NASA NTRS1981

On the geodetic stability of the Goddard Optical Research Facility

Seismic observations of earthquakes and blasts, geologic analysis of Landsat images, and a search of the historical record was examined. However, no evidence for tectonic motion was found. Some faulting is present in the area but no evidence of seismic activity was found. No elastic resonances in the range from 0.3 to 15 Hz were found. It is concluded that, except for ground water induced changes, the facility is stable at least to the 0.5 cm level.

Webster, W. J., Jr.↗
NASA NTRS1982

Geodetic control

The U.S. Horizontal Network is described for the years 1900 and 1931, and then compared with the current status of the network. North American Datum for 1946 and 1981 are also described. Relative accuracy between directly connected adjacent points were reviewed along with absolute accuracy.

Gergen, J.↗
NASA NTRS1983

Geodetic distance measuring apparatus

A mode locked laser system including a laser device and its peripheral components is utilized for deriving two mutually phase locked optical wavelength signals and one phase locked microwave CW signal which respectively traverse the same distance measurement path. Preferably the optical signals are comprised of pulse type signals. Phase comparison of the two optical wavelength pulse signals is used to provide a measure of the dry air density while phase comparison of one of the optical wavelength pulse signals and the microwave CW signal is used to provide a measure of the wet or water vapor density of the air. From these measurements is computed in means of the distance to be measured corrected for the atmospheric dry and water vapor densities in the measurement path.

Abshire, J. B.↗