Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “GEM”

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.

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

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

A global station coordinate solution based upon camera and laser data - GSFC 1973

Results for the geocentric coordinates of 72 globally distributed satellite tracking stations consisting of 58 cameras and 14 lasers are presented. The observational data for this solution consists of over 65,000 optical observations and more than 350 laser passes recorded during the National Geodetic Satellite Program, the 1968 Centre National d'Etudes Spatiales/Smithsonian Astrophysical Observatory (SAO) Program, and International Satellite Geodesy Experiment Program. Dynamic methods were used. The data were analyzed with the GSFC GEM and SAO 1969 Standard Earth Gravity Models. The recent value of GM = 398600.8 cu km/sec square derived at the Jet Propulsion Laboratory (JPL) gave the best results for this combination laser/optical solution. Solutions are made with the deep space solution of JPL (LS-25 solution) including results obtained at GSFC from Mariner-9 Unified B-Band tracking. Datum transformation parameters relating North America, Europe, South America, and Australia are given, enabling the positions of some 200 other tracking stations to be placed in the geocentric system.

Marsh, J. G.↗
NASA NTRS1973

Detailed geoid computations for GEOS-C altimeter experiment areas

The GEOS-C spacecraft is scheduled to carry onboard a radar altimeter for the purpose of measuring the geoid undulations in oceanic areas. An independently derived geoid map will provide a valuable complement to these experiments. A detailed gravimetric geoid is presented for the Atlantic and northeast Pacific Ocean areas based upon a combination of the Goddard Space Flight Center GEM-6 earth model and surface 1 deg x 1 deg gravity data. As part of this work a number of satellite derived gravity models were evaluated to establish the model which best represented the long wave length features of the geoid in the above mentioned area. Comparisons of the detailed geoid with the astrogeodetic data provided by the National Ocean Survey and dynamically derived tracking station heights indicate that the accuracy of this combined geoid is on the order of 2 meters or better where data was dense and 5 to 7 meters where data was less dense.

Marsh, J. G.↗
NASA NTRS1973

Global detailed gravimetric geoid

A global detailed gravimetric geoid has been computed by combining the Goddard Space Flight Center GEM-4 gravity model derived from satellite and surface gravity data and surface 1 deg-by-1 deg mean free air gravity anomaly data. The accuracy of the geoid is + or - 2 meters on continents, 5 to 7 meters in areas where surface gravity data are sparse, and 10 to 15 meters in areas where no surface gravity data are available. Comparisons have been made with the astrogeodetic data provided by Rice (United States), Bomford (Europe), and Mather (Australia). Comparisons have also been carried out with geoid heights derived from satellite solutions for geocentric station coordinates in North America, the Caribbean, Europe, and Australia.

Vincent, S.↗
NASA NTRS1973

Mapping coastal vegetation, land use and environmental impact from ERTS-1

The author has identified the following significant results. Vegetation map overlays at a scale of 1:24,000 compiled by multispectral analysis from NASA aircraft imagery for all of Delaware's wetlands are being used as ground truth for ERTS-1 mapping and by state agencies for wetlands management. Six major vegetation species were discriminated and mapped, including percentages of minor species. Analogue enhancements of wetlands vegetation and dredge-fill operations have been produced using General Electric's GEMS data processing and ERTS-1 false color composites. Digital, thematic land use, and vegetation mapping of entire Delaware Bay area is in progress using Bendix Corporation's Earth Resources Data System and ERTS-1 digital tapes. Statistical evaluation of target-group selection reliability has been completed. Three papers have been published on ERTS-1 coastal vegetation and land use. Local and state officials are participating in the ERTS-1 program as co-investigators.

Klemas, V.↗
NASA NTRS1974

Global detailed geoid computation and model analysis

Comparisons and analyses were carried out through the use of detailed gravimetric geoids which we have computed by combining models with a set of 26,000 1 deg x 1 deg mean free air gravity anomalies. The accuracy of the detailed gravimetric geoid computed using the most recent Goddard earth model (GEM-6) in conjunction with the set of 1 deg x 1 deg mean free air gravity anomalies is assessed at + or - 2 meters on the continents of North America, Europe, and Australia, 2 to 5 meters in the Northeast Pacific and North Atlantic areas, and 5 to 10 meters in other areas where surface gravity data are sparse. The R.M.S. differences between this detailed geoid and the detailed geoids computed using the other satellite gravity fields in conjuction with same set of surface data range from 3 to 7 meters.

Marsh, J. G.↗
NASA NTRS1974

High angular resolution cosmic X-ray astronomy observations in the energy range 0.15-2 keV and XUV observations of nearby stars from an attitude controlled rocket

The construction of a two dimensional focusing Wolter Type I mirror system for X-ray and XUV astronomical observations from an Astrobee F sounding rocket is described. The mirror design goal will have a one degree field, a 20-arc seconds resolution, an effective area of about 50 sq cm at 1 keV and 10 sq cm at 0.25 keV on axis. A star camera provides aspect data to about 15-arc seconds. Two detectors are placed at the focus with an interchange mechanism to allow a detector change during flight. The following specific developments are reported: (1) position sensitive proportional counter development; (2) channel plate multiplier development; (3) telescope mirror development and payload structure; (4) Australian rocket flight results; (5) Comet Kohoutek He I observation; and (6) Vela, Puppis A, and Gem-Mon bright patch observations.

Garmire, G. P.↗
NASA NTRS1974

The spectral types of the members of VV Cephei systems from photometric analysis

The photometric data for ten binary systems that have a highly luminous red primary with a less luminous blue companion have been analyzed, and the spectral types of the member stars have been determined. Eight of these systems are VV Cephei-type systems; one, alpha Sco, has a more distant blue companion, while XX Per has a blue companion that is probably too distant to induce emission. It has been determined that the blue companion of WY Gem is an intrinsic variable.

Wawrukiewicz, A. S.↗
NASA NTRS1975

Earth and ocean physics

A procedure for obtaining a parameterization of the marine geoid for suitable orthogonality properties in altimetry data is discussed. The application of the technique to the Puerto Rico trench is explained and a map of the data is developed. The Goddard Earth Model (GEM-6) is described to show the method for determining the earth gravity field using data obtained from satellite tracking stations. The derivation of a global ocean tide model from satellite data is explained. The influence of solid earth and ocean tides on the inclination of GEOS-1 is plotted. The delineation of the geographical fracture pattern and boundary system of the tectonic plates using ERTS satellite is shown.

Source record↗
NASA NTRS1975

Time variations of UV emission features of Be stars

The UV spectra of three Be stars (gamma Cas, sigma Tau, eta Cen) were studied. Of the six Be stars observed in the first four lines of the Balmer series, three stars showed at least one of the Balmer lines to be variable in the equivalent width amounting to a few percent with time scales of 3 to 30 minutes. Photoelectric spectrum scans of five southern Wolf-Rayet stars showed night-to-night variations. A simple model is proposed to account for the behavior of these emission lines. Scans of gamma square Vel showed rapid variations of emission strengths of He II 4686 and C III - IV 4650. These variations have time scales of 1 minute and longer. Night-to-night variations were also found. Scans of four Be stars in H alpha showed a definite variation of 3 to 4 percent, with time scales of 1 minute and longer in sigma Tau. In 48 Per and kappa Dra the variations are not as well established. No variation of any significance was found for nu Gem.

Bahng, J. D. R.↗
NASA NTRS1975

Detailed gravimetric geoid confirmation of short wavelength features of sea surface topography detected by the Skylab S-193 altimeter in the Atlantic Ocean

A detailed gravimetric geoid was computed for the Northwest Atlantic Ocean and Caribbean Sea area in support of the calibration and evaluation of the GEOS-C altimeter. This geoid, computed on a 15 ft. x 15 ft. grid was based upon a combination of surface gravity data with the GSFC GEM-6 satellite derived gravity data. A comparison of this gravimetric geoid with 10 passes of SKYLAB altimeter data is presented. The agreement of the two data types is quite good with the differences generally less than 2 meters. Sea surface manifestations of numerous short wavelength (approximately 100 km) oceanographic features are now indicated in the gravimetric geoid and are also confirmed by the altimetry data.

Marsh, J. G.↗
NASA NTRS1974

Evidence for a corona of beta Geminorum

A spectrometer was used on the satellite Copernicus to observe a chromospheric L alpha emission from the K0 giant beta Gem at 1218.4 A. This emission appears to be in the corona at temperatures near 260,000 deg K, since the ion it is identified with requires 77.4 eV to be produced.

Gerola, H.↗
NASA NTRS1974

Detailed gravimetric geoid for the GEOS-C altimeter calibration area

The GEOS-C spacecraft scheduled for launch in late 1974 will carry a radar altimeter for the purpose of measuring sea surface topography. In order to calibrate and evaluate the performance of the altimeter system, ground truth data are required. In this respect a detailed gravimetric geoid has been computed for the GEOS-C altimeter calibration area in the Atlantic Ocean off the East Coast of the U.S. This geoid is based upon a combination of mean free air surface gravity anomalies and the Goddard Space Flight Center GEM-6 satellite-derived spherical harmonic coefficients. Surface gravity anomalies have been used to provide information on the short wave length undulations of the geoid while the satellite-derived coefficients have provided information on the long wave length components. As part of these analyses, GSFC, SAO and OSU satellite-derived gravity models were used in the computations. Although geoid heights based upon the various satellite models differed by as much as 30 meters in the Southern Hemisphere, the differences in this Atlantic Ocean area were less than 4 meters.

Marsh, J. G.↗
NASA NTRS1974

Global detailed gravimetric geoid

A global detailed gravimetric geoid has been computed by combining the Goddard Space Flight Center GEM-4 gravity model derived from satellite and surface gravity data and surface 1 x 1-deg mean free-air gravity anomaly data. The accuracy of the geoid is plus or minus 2 meters on continents, 5 to 7 meters in areas where surface gravity data are sparse, and 10 to 15 meters in areas where no surface gravity data are available. Comparisons have been made with the astrogeodetic data provided by Rice (United States), Bomford (Europe), and Mather (Australia). Comparisons have also been carried out with geoid heights derived from satellite solutions for geocentric station coordinates in North America, the Caribbean, Europe and Australia.

Vincent, S.↗
NASA NTRS1974

Results from the direct combination of satellite and gravimetric data

Results have been obtained for the solution of 184 15-deg equal-area blocks directly from the analysis of satellite orbits, and from a combination of the satellite results with terrestrial gravity material. This test computation, made to verify the method, used 17,632 optical observations from ten satellites in 29 arcs averaging in length seven days. Analysis of the satellite results were made by comparing the solved for anomalies with the terrestrial anomaly set, and by developing the solved for anomalies into potential coefficients which were compared to the GEM 3 set of potential coefficients to degree 12. These comparisons indicated improvement in each solution as more arcs were added. The programs used in this solution can easily be used to solve for smaller size blocks and handle additional data types. The only limitation will be computer core availability and computer time.

Rapp, R. H.↗
NASA NTRS1975

Australian rocket results

Cen X-3 was observed twice. A pulse profile and spectrum was obtained in the 2- to 10-keV band, but no soft flux was detected. Vela X-1 was observed to have a rapid flickering characteristic on time scales down to 0.25 sec and a hard spectrum. The source 3U 0614+09 was observed and found to have a softer spectrum (kT of about 4 keV) and an intensity comparable to that of earlier observations. The source eta Car was not detected at a level of 0.03 ph/sq cm/sec in the band from 0.2 to 1.5 keV, and the Large Magellanic Cloud was observed in the band from 0.5 to 1.5 keV at a level of about 0.1 ph/sq cm/sec. Two soft extended regions were observed in Gem-Mon and Eridanus.

Garmire, G.↗
NASA NTRS1976

High spatial resolution multi-color observations of Neptune during occultation by the moon

Preparations for the observation of Mars occultation using the 36 inch telescope on a C-141 airborne observatory were described, including technical improvements made to existing equipment. The abstracts of the following four publications supported by the grant were presented: (1) atmosphere composition from refractivity measurements made during occultations, (2) how big is lapetus?, (3) the diameter of Titan, (4) design and operating characteristics of voltage to frequency converters suited for occultation work. The planned observation of the April 8, 1976 occultation of the epsilon Gem star from the C-141 airborne observatory was described.

Veverka, J.↗
NASA NTRS1976

Strain buildup and release, earthquake prediction and selection of VLB sites for the margins of the North Pacific

Microearthquake studies of the southern section of the San Andreas fault system were conducted in order to elucidate the role of known but little studied complications in the fault system which could affect the SAFE measurement. Data reduction from microearthquake studies in Baja California, Mexico, was completed. In addition, styles of deformation on the Alpine fault in New Zealand and on the San Andreas fault were compared. Sections of these faults with comparable physical characteristics seem to deform in a similar manner, indicating that deformation style is controlled by certain fundamental relations and will continue in the future. The geology of eastern New Guinea is also discussed. Deformation in the area is proposed to be related to collision of a series of island arcs with central New Guinea, which is part of the Australian continent. Among other unusual properties, eastern New Guinea contains the highest anomaly of the gravimetrically determined geoid based on GEM 6 and surface gravity data.

Scholz, C. H.↗
NASA NTRS1975

X-ray emission from U Geminorum and the radio spur at l about 200 deg

Rocket X-ray data on U Geminorum obtained at phase 0.062 during a quiescent period are shown to yield an upper limit of 7 times 10 to 31 erg/sec for the X-ray luminosity in the 150 to 280 eV band. This limit is compared with the recent reported X-ray observation of SS Cygni during an active period and the prediction of Warner's model for U Gem. It is suggested, in agreement with Berkhuijsen, that a soft X-ray feature at l about 200 deg and b about +20 deg arises from a radio spur at that location.

Novick, R.↗