SEARCH · Engineering Papers

Results for “geodetics”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44

All sources NASA NTRS DOE OSTI

NASA NTRS1973

Earth's gravity field to the eighteenth degree and geocentric coordinates for 104 stations from satellite and terrestrial data

Geodetic parameters describing the earth's gravity field and the positions of satellite-tracking stations in a geocentric reference frame were computed. These parameters were estimated by means of a combination of five different types of data: routine and simultaneous satellite observations, observations of deep-space probes, measurements of terrestrial gravity, and surface-triangulation data. The combination gives better parameters than does any subset of data types. The dynamic solution used precision-reduced Baker-Nunn observations and laser range data of 25 satellites. Data from the 49-station National Oceanic and Atmospheric Administration BC-4 network, the 19-station Smithsonian Astrophysical Observatory Baker-Nunn network, and independent camera stations were employed in the geometrical solution. Data from the tracking of deep-space probes were converted to relative longitudes and distances to the earth's axis of rotation of the tracking stations. Surface-gravity data in the form of 550-km squares were derived from 19,328 1 deg X 1 deg mean gravity anomalies.

Gaposchkin, E. M.↗

NASA NTRS1974

Contributions of satellite-determined gravity results in geodesy

Different forms of the theoretical gravity formula are summarized and methods of standardization of gravity anomalies obtained from satellite gravity and terrestrial gravity data are discussed in the context of three most commonly used reference figures, e.g., International Reference Ellipsoid, Reference Ellipsoid 1967, and Equilibrium Reference Ellipsoid. These methods are important in the comparison and combination of satellite gravity and gravimetric data as well as the integration of surface gravity data, collected with different objectives, in a single reference system. For ready reference, tables for such reductions are computed. Nature of the satellite gravity anomalies is examined to aid the geophysical and geodetic interpretation of these anomalies in terms of the tectonic features of the earth and the structure of the earth's crust and mantle. Computation of the Potsdam correction from satellite-determined geopotential is reviewed. The contribution of the satellite gravity results in decomposing the total observed gravity anomaly into components of geophysical interest is discussed. Recent work on the possible temporal variations in the geogravity field is briefly reviewed.

Khan, M. A.↗

NASA NTRS1973

Free geometric adjustment of the SECOR Equatorial Network (Solution SECOR-27)

The basic purpose of this experiment is to compute reduced normal equations from the observational data of the SECOR Equatorial Network obtained from DMA/Topographic Center, D/Geodesy, Geosciences Div. Washington, D.C. These reduced normal equations are to be combined with reduced normal equations of other satellite networks of the National Geodetic Satellite Program to provide station coordinates from a single least square adjustment. An individual SECOR solution was also obtained and is presented in this report, using direction constraints computed from BC-4 optical data from stations collocated with SECOR stations. Due to the critical configuration present in the range observations, weighted height constraints were also applied in order to break the near coplanarity of the observing stations.

Mueller, I. I.↗

NASA NTRS1973

The 1973 Smithsonian standard earth (3)

The origins of the satellite geodesy program are described, starting with the International Geophysical Year, continuing through a number of international programs, and culminating with the National Geodetic Satellite Program. The philosophical basis for the Baker-Nunn camera and the laser ranging system, the evolution of international scientific cooperation, and the significance of the results are discussed.

Garoschkin, E. M.↗

NASA NTRS1971

The gravimetric geodesy investigation

The Gravimetric Geodesy Investigation which will utilize altimeter and satellite-to-satellite tracking data from GEOS-C, ATS-F, and other spacecraft as appropriate to improve our knowledge of the earth's gravitational field is discussed. This investigation is interrelated with the study of oceanographic phenomena such as those associated with tides and currents, hence the latter are considered together with gravitational effects in the analysis of the data. The oceanographic effects, each of the order of a meter or two in amplitude and with still smaller uncertainties does not seriously hamper the altimeter gravimetric studies at the five meter level. Laser and satellite-to-satellite tracking data, when combined with the altimeter results, should provide the basis for such studies over wide areas of the ocean surface. Laser and conventional geodetic tracking data from ISAGEX and succeeding campaigns will provide a valuable framework for these analyses.

Siry, J. W.↗

NASA NTRS1972

The design, construction and testing of the optics for a 147-cm-aperture telescope

Geodetic optics research for the Air Force Cambridge Research Laboratories (AFCRL) is described. The work consisted mainly of the fabrication of the optical components for a telescope with a 152-cm-diam (60-in.) primary mirror masked down to 147-cm-diam for use by the AFCRL for a lunar ranging experiment. Among the achievements of this contract were the following: completion of the primary and secondary mirrors for a high-quality 147-cm-diam telescope system in eight months from the start of edging the primary; manufacture and testing of a unique center mount for the primary according to an AFCRL design that allowed for a thin-edged and therefore less-massive mirror; and development of a quantitative analysis of the wire test for calculating the departure of the mirror figure from the design figure quickly and accurately after each polishing step. This analysis method in conjunction with a knowledge of polishing rates for given weights and diameters of tools, mirror, and polishing materials should considerably reduce the polishing time required for future large mirrors.

Buchroeder, R. A.↗

NASA NTRS1973

Analysis of the relativistic orbiting gyroscope experiment

A gyroscope experiment designed to measure both the geodetic and the Lense-Thirring precessions to an accuracy of 0.01 arc-second per year appears economically and technically feasible. It is estimated that an accuracy of about one part in 10 to the 11th power in an Eotvos experiment would be required to detect a situation in which the weak interaction contributed to the inertial masses but not the gravitational masses of nuclei; a correspondingly higher accuracy in the experiment is required to detect the situation where the weak interaction contributed to the gravitational masses some fraction between zero and one of its contribution to the inertial masses.

Coulter, A. C.↗

NASA NTRS1974

GEOS observation systems intercomparison investigation results

The results of an investigation designed to determine the relative accuracy and precision of the different types of geodetic observation systems used by NASA is presented. A collocation technique was used to minimize the effects of uncertainties in the relative station locations and in the earth's gravity field model by installing accurate reference tracking systems close to the systems to be compared, and by precisely determining their relative survey. The Goddard laser and camera systems were shipped to selected sites, where they tracked the GEOS satellite simultaneously with other systems for an intercomparison observation.

Berbert, J. H.↗

NASA NTRS1974

Geoscience instrumentation

Geoscience instrumentation systems are considered along with questions of geoscience environment, signal processing, data processing, and design problems. Instrument platforms are examined, taking into account ground platforms, airborne platforms, ocean platforms, and space platforms. In situ and laboratory sensors described include acoustic wave sensors, age sensors, atmospheric constituent sensors, biological sensors, cloud particle sensors, electric field sensors, electromagnetic field sensors, precision geodetic sensors, gravity sensors, ground constituent sensors, horizon sensors, humidity sensors, ion and electron sensors, magnetic field sensors, tide sensors, and wind sensors. Remote sensors are discussed, giving attention to sensing techniques, acoustic echo-sounders, gamma ray sensors, optical sensors, radar sensors, and microwave radiometric sensors.

Wolff, E. A.↗

NASA NTRS1972

GEODYN programmers guide, volume 2, part 1

A guide to the GEODYN Program is presented. The program estimates orbit and geodetic parameters. It possesses the capability to estimate that set of orbital elements, station positions, measurement biases, and a set of force model parameters such that the orbital tracking data from multiple arcs of multiple satellites best fit the entire set of estimated parameters. GEODYN consists of 113 different program segments, including the main program, subroutines, functions, and block data routines. All are in G or H level FORTRAN and are currently operational on GSFC's IBM 360/95 and IBM 360/91.

Mullins, N. E.↗

NASA NTRS1972

Very Long Baseline Interferometry (VLBI) earth physics

The characteristics of the Michelson/Pease stellar interferometer are discussed. An analog of the interferometer using radio waves is described. The use of a conventional hard-wired interferometer with very long base line interferometry (VLBI) is analyzed. Mathematical models are developed to analyze the VLBI techniques. A summary of VLBI geodetic experiments is tabulated. The concept and application of the astronomical radio interferometric earth surveys (ARIES) are reported. A schematic diagram of ARIES implementation is provided.

Macdoran, P. F.↗

NASA NTRS1973

DMA precise time and time interval requirements

Defense Mapping Agency timing requirements ranging from milliseconds to tenths of nanoseconds and its use of geodetic astronomy and satellite geodesy programs are discussed in detail.

Carnahan, R. H.↗

NASA NTRS1972

GEODYN operations description, volume 3

The operating and set-up procedures for the multi-satellite, multi-arc GEODYN- Orbit Determination program are described. All system output is analyzed. The GEODYN Program is the nucleus of the entire GEODYN system. It is a definitive orbit and geodetic parameter estimation program capable of simultaneously processing observations from multiple arcs of multiple satellites. GEODYN has two modes of operation: (1) the data reduction mode and (2) the orbit generation mode.

Martin, T. V.↗

NASA NTRS1975

Project GEOS-C

An oceanographic-geodetic satellite, designated Geodynamics Experimental Ocean Satellite-C (GEOS-C), an earth-orbiting spacecraft designed to measure precisely the topography of the ocean surface and the sea state (wave height, wave period, wave propagation direction) is described. Launch operations, spacecraft description, and mission objectives are included along with a brief flight history of the NASA satellite geodesy program. Principal investigations to be performed by the GEOS-C mission are discussed.

Source record↗

NASA NTRS1974

Goddard earth models (5 and 6)

A comprehensive earth model has been developed that consists of two complementary gravitational fields and center-of-mass locations for 134 tracking stations on the earth's surface. One gravitational field is derived solely from satellite tracking data. This data on 27 satellite orbits is the most extensive used for such a solution. A second solution uses this data with 13,400 simultaneous events from satellite camera observations and surface gravimetric anomalies. The satellite-only solution as a whole is accurate to about 4.5 milligals as judged by the surface gravity data. The majority of the station coordinates are accurate to better than 10 meters as judged by independent results from geodetic surveys and by Doppler tracking of both distant space probes and near earth orbits.

Lerch, F. J.↗

NASA NTRS1974

Application of very long baseline interferometry to Astrometry and Geodesy: effects of frequency standard instability on accuracy

The accuracy of geodetic and astrometric information obtained from very long baseline interferometry (VLBI) observations is dependent upon the stability of the frequency standard, or clock, used at each site of VLBI array. The sensitivities of two hydrogen maser frequency standards of different design to pressure, temperature, and magnetic field variations were measured; and, for one of the standards, sensitivity was found to be severe enough to degrade the information content of VLBI measurements. However, the effect on the geometric and astrometric information of such clock instabilities, with time scales of hours or greater, can be sharply reduced through the use of differencing techniques.

Clark, T. A.↗

NASA NTRS1975

Sea surface determination from space: The GSFC geoid

The determination of the sea surface/geoid and its relative variation were investigated and results of the altimeter experiment on Skylab to test the geoid are discussed. The spaceborne altimeter on Skylab revealed that the sea surface of the world's oceans can be measured with an accuracy in the meter range. Surface variations are discussed as they relate to those computed from satellite orbital dynamics and ground based gravity data. The GSFC geoid was constructed from about 400,000 satellite tracking data (range, range rate, angles) and about 20,000 ground gravity observations. One of the last experiments on Skylab was to measure and/or test this geoid over almost one orbit. It was found that the computed water surface deviates between 5 to 20 m from the measured one. Further outlined are the influence of orbital errors on the sea surface, and numerical examples are given based upon real tracking data. Orbital height error estimates were computed for geodetic type satellites and are found to be in the order of 0.2 to 5 meters.

Vonbun, F. O.↗

NASA NTRS1975

Contribution of Apollo lunar photography to the establishment of selenodetic control

Among the various types of available data relevant to the establishment of geometric control on the moon, the only one covering significant portions of the lunar surface (20%) with sufficient information content, is lunar photography, taken at the proximity of the moon from lunar orbiters. The idea of free geodetic networks is introduced as a tool for the statistical comparison of the geometric aspects of the various data used. Methods were developed for the updating of the statistics of observations and the a priori parameter estimates to obtain statistically consistent solutions by means of the optimum relative weighting concept.

Dermanis, A.↗