381
381
Aug 1, 2010
08/10
by
Mucklow, Glenn H
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The development of an Automatic TV Tracking System for NASA's mobile 61 cm aperture Satellite Photometric Observatory is described. The analysis techniques used to match the FOV and resolutions to changing seeing conditions are covered in details. Theoretical reasons for such matching of general interest are discussed. It is shown that the energy density in a satellite image is 11 times greater during good seeing conditions than during typical seeing conditions. The Z7987 image tube is shown to...
Topics: COEFFICIENTS, MAPS, OCEANS, SATELLITE ALTIMETRY, SPHERICAL HARMONICS, TIDES, GEOSAT SATELLITES,...
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194
May 23, 2011
05/11
by
Plucinsky, Pau
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The subject grant is for the analysis of ASCA observations of two well-known galactic Supernova Remnants, CTB 109 and MSH 15-56. The purpose of the proposal is to study spectral differences as a function of position within each of the remnants. For CTB 109 we are attempting to understand how the unusual semi-circular structure evolved. For MSH 15-56, we are attempting to understand the nature of the emission in the bright central region and around the outer edge of the remnant.
Topics: GULF STREAM, VORTICES, OCEAN MODELS, OCEAN SURFACE, SATELLITE ALTIMETRY, MATHEMATICAL MODELS,...
131
131
May 23, 2011
05/11
by
Gerard, J. C.; Franke, K. A; Grodent, D.; Prange, R.; Waite, J. H.; Gladstone, G. R.; Dols, V.; Paresce, F.; Storrs, A.; BenJaffel, L.
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Two sets of ultraviolet images of the Jovian north aurora were obtained with the Faint Object Camera on board the Hubble Space Telescope. The first series shows an intense discrete arc in near corotation with the planet. The maximum apparent molecular hydrogen emission rate corresponds to an electron precipitation of approximately 1 watt per square meter, which is about 30,000 times larger than the solar heating by extreme ultraviolet radiation. Such a particle heating rate of the auroral upper...
Topics: LAND ICE, WINTER, SEASAT SATELLITES, GEOSAT SATELLITES, ELEVATION, SATELLITE ALTIMETRY, RADIO...
I have derived the vertical profiles of apparent heating Q and Q2 by using 3-hourly balloon sounding data from the ARM SGP sounding array for three IOPs in 2000. These IOPs cover the periods from 3/1 to 3/22, from 9/25 to 10/8, and from 11/27 to 12/22. These heating profiles will be collocated with the TRMM heating profiles for validation studies once the TRMM profiles become available to the investigators. I have also produced the objective analyses of Q1, Q2 and forcing fields for the...
Topics: NASA Technical Reports Server (NTRS), BALLOON SOUNDING, LATENT HEAT, SATELLITE OBSERVATION, TRMM...
The purpose of this report is to present the results of an analysis of the white noise in Geosat Follow-On (GFO) altimeter data. The Repeat-Track Method was used to determine noise level. This approach was developed at TASC and has been used to quantify noise levels of all previous satellite altimeter missions. The GFO altimeter was designed to have an RMS white noise level of less than 3.5 centimeters for significant wave height less than 2 meters. The results of the analysis presented here...
Topics: NASA Technical Reports Server (NTRS), ALTIMETERS, NOISE INTENSITY, WHITE NOISE, NOISE MEASUREMENT,...
208
208
May 23, 2011
05/11
by
Trasco, John D
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A joint agreement between NASA/Goddard and The University of Maryland currently supports cooperative research in Satellite Based Studies of Photons and Charged Particles in the following areas: 1) Detection of cosmic rays and studies of the solar modulation of galactic cosmic rays; 2) Research with several past and upcoming X-ray satellites; 3) High resolution gamma-ray spectroscopy of celestial sources; 4) Theoretical astrophysics.
Topics: ALTIMETERS, CORRELATION COEFFICIENTS, TIME SERIES ANALYSIS, VARIABILITY, ASSIMILATION, GULF STREAM,...
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188
May 31, 2011
05/11
by
Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Martens, Christopher S
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Among the most fundamental constraints governing the distribution of microorganisms in the environment is the availability of chemical energy at biologically useful levels. To assess the minimum free energy yield that can support microbial metabolism in situ, we examined the thermodynamics of H2-consuming processes in anoxic sediments from Cape Lookout Bight, NC, USA. Depth distributions of H2 partial pressure, along with a suite of relevant concentration data, were determined in sediment cores...
Topics: ANTARCTIC REGIONS, RADIO ALTIMETERS, ICEBERGS, GEOSAT SATELLITES, ELECTRICAL GROUNDING, DISTANCE,...
The purpose of this document is to present and document GEOSAT Follow-On (GFO) performance analyses and results. This is the eighth Assessment Report since the initial report. This report extends the performance assessment since acceptance to 27 December 2007. Since launch, a variety of GFO performance studies have been performed: Appendix A provides an accumulative index of those studies. We began the inclusion of analyses of the JASON altimeter after the end of the Topographic Experiment...
Topics: NASA Technical Reports Server (NTRS), GEOSAT SATELLITES, ALTIMETERS, LAUNCHING, TOPEX, TOPOGRAPHY,...
Since altimetry data are not really old enough to use the term data archaeology, Mr. Cheney referred to the stewardship of these data. He noted that it is very important to document the basis for an altimetry data set as the algorithms and corrections used to arrive at the Geophysical Data Record (GDR) have been improving and are continuing to improve the precision of sea level data derived from altimetry. He noted that the GEOSAT Exact Repeat Mission (ERM) data set has recently been...
Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, CD-ROM, GEOPHYSICS, GEOSAT SATELLITES,...
We proposed to construct a complete bathymetric map of the oceans at a 3-10 km resolution by combining all of the available depth soundings collected over the past 30 years with high resolution marine gravity information provided by the Geosat, ERS-1/2, and Topex/Poseidon altimeters. Detailed bathymetry is essential for understanding physical oceanography and marine geophysics. Currents and tides are controlled by the overall shapes of the ocean basins as well as the smaller sharp ocean ridges...
Topics: NASA Technical Reports Server (NTRS), BATHYMETERS, TOPOGRAPHY, OCEAN BOTTOM, TOPEX, POSEIDON...
The purpose of this document is to present and document GEOSAT Follow-On (GFO) performance analyses and results. This is the ninth Assessment Report since the initial report and is our final one. This report extends the performance assessment since acceptance on November 29, 2000 to the end of mission (EOM) on October 22, 2008. Since launch, February 10, 1998 to the EOM, we performed a variety of GFO performance studies; Appendix A provides an accumulative index of those studies. We began the...
Topics: NASA Technical Reports Server (NTRS), GEOSAT SATELLITES, ALTIMETERS, PERFORMANCE, RELIABILITY,...
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An ultrasensitive displacement sensing device for use in accelerometers, pressure gauges, temperature transducers, and the like, comprises a sputter deposited, multilayer, magnetoresistive field sensor with a variable electrical resistance based on an imposed magnetic field. The device detects displacement by sensing changes in the local magnetic field about the magnetoresistive field sensor caused by the displacement of a hard magnetic film on a movable microstructure. The microstructure,...
Topics: ALTIMETERS, ATTITUDE (INCLINATION), TOPEX, SEASAT SATELLITES, POSEIDON SATELLITE, CALIBRATING, WIND...
230
230
May 31, 2011
05/11
by
Prudhomme, C.; Rovas, D. V.; Veroy, K.; Machiels, L.; Maday, Y.; Patera, A. T.; Turinici, G
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We present a technique for the rapid and reliable prediction of linear-functional outputs of elliptic (and parabolic) partial differential equations with affine parameter dependence. The essential components are (i) (provably) rapidly convergent global reduced basis approximations, Galerkin projection onto a space W(sub N) spanned by solutions of the governing partial differential equation at N selected points in parameter space; (ii) a posteriori error estimation, relaxations of the...
Topics: ANTARCTIC REGIONS, SATELLITE-BORNE RADAR, RELIEF MAPS, TERRAIN, GLACIERS, SURFACE ROUGHNESS,...
I discuss the implementation of an H2O transport scheme in the Global Modeling Initiative (GMI) model.
Topics: NASA Technical Reports Server (NTRS), STRATOSPHERE, WATER VAPOR, CLIMATE MODELS, HYDROLOGY MODELS,...
Model computations show that changes of sampling interval introduce only 0.3 cm changes, whereas zero padding provides an improvement of more than 5 cm in the fast Fourier transformation (FFT) generated geoid. For the Global Positioning System (GPS) survey of Franklin County, Ohio, the parameters selected as a result of model computations, allow large reduction in local data requirements while still retaining the cm accuracy when tapering and padding is applied. The results are shown in tables.
Topics: NASA Technical Reports Server (NTRS), FAST FOURIER TRANSFORMATIONS, GEOIDS, GRAVIMETERS,...
Maps and tables for the global ocean tides, 69 degree N to 68 degree S, derived from two years of Geosat altimetry are presented. Global maps of local and Greenwich admittance of the (altimetric) ocean tide, and maps of amplitude and Greenwich phase lag of the ocean tide are shown for M(sub 2), S(sub 2), N(sub 2), O(sub 1), and K(sub 1). Larger scale maps of amplitude and phases are also shown for regional areas of special interest. Spherical harmonic coefficients of the ocean tide through...
Topics: NASA Technical Reports Server (NTRS), COEFFICIENTS, MAPS, OCEANS, SATELLITE ALTIMETRY, SPHERICAL...
The goal of the Navy's GEOSAT Follow-On (GFO) mission is to map the topography of the world's oceans in both real time (operational) and post processed modes. Currently, the best candidate for supplying the required orbit accuracy is the Global Positioning System (GPS). The purpose of this fellowship was to determine the expected orbit accuracy for GFO in both the real time and post-processed modes when using GPS tracking. This report presents the work completed through the ending date of the...
Topics: NASA Technical Reports Server (NTRS), ERROR ANALYSIS, GEOSAT SATELLITES, GLOBAL POSITIONING SYSTEM,...
174
174
May 23, 2011
05/11
by
Murawski, K.; Steinolfson, R. S
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Numerical simulations are performed in the framework of nonlinear two-dimensional magnetohydrodynamics to investigate the influence of mass loading on the solar wind interaction with Venus. The principal physical features of the interaction of the solar wind with the atmosphere of Venus are presented. The formation of the bow shock, the magnetic barrier, and the magnetotail are some typical features of the interaction. The deceleration of the solar wind due to the mass loading near Venus is an...
Topics: GEOSAT SATELLITES, SIMULATION, SATELLITE OBSERVATION, RESOLUTION, OCEAN SURFACE, OCEAN CURRENTS,...
From simulations, the orbit error can be assumed to be a slowly varying sine wave with a predominant wavelength comparable to the Earth's circumference. Thus, one can derive analytically the error committed in representing the orbit error along a segment of the satellite ground track by a bias; by a bias and tilt (linear approximation); or by a bias, tilt, and curvature (quadratic approximation). The result clearly agrees with what is obvious intuitively, i.e., (1) the fit is better with more...
Topics: NASA Technical Reports Server (NTRS), APPROXIMATION, ERROR ANALYSIS, ORBIT CALCULATION, SATELLITE...
Long-term simultaneous global coverage of AVHRR sea surface temperature, SSMI surface wind speed, GEOSAT sea surface height, and ARGOS buoy drift began in 1987. Methodology to create annual atlases of monthly mean distributions is described.
Topics: NASA Technical Reports Server (NTRS), ANNUAL VARIATIONS, GEOSAT SATELLITES, OCEAN SURFACE,...
The US Navy's Geosat Follow-On (GFO) Mission, launched on February 10, 1998, is the latest in a series of altimetric satellites which include Seasat, Geosat, ERS-1, and TOPEX/POSEIDON (T/P). The purpose of this report is to document the GFO altimeter performance determined from the analyses and results performed by the NASA/GSFC/Wallops altimeter calibration team. It is the first of an anticipated series of NASA/GSFC/Wallops' GFO performance documents, each of which will update assessment...
Topics: NASA Technical Reports Server (NTRS), RADIO ALTIMETERS, PERFORMANCE TESTS, CALIBRATING, GEOSAT...
The dynamical consequences of constraining a numerical model with sea surface height data have been investigated. The model used for this study is a quasigeostrophic model of the Gulf Stream region. The data that have been assimilated are maps of sea surface height obtained as the superposition of sea surface height variability deduced from the Geosat altimeter measurements and a mean field constructed from historical hydrographic data. The method used for assimilating the data is the nudging...
Topics: NASA Technical Reports Server (NTRS), GULF STREAM, OCEAN MODELS, OCEAN SURFACE, SATELLITE...
The computation is described of a geopotential model to deg 360, a sea surface topography model to deg 10/15, and adjusted Geosat orbits for the first year of the exact repeat mission (ERM). This study started from the GEM-T2 potential coefficient model and it's error covariance matrix and Geosat orbits (for 22 ERMs) computed by Haines et al. using the GEM-T2 model. The first step followed the general procedures which use a radial orbit error theory originally developed by English. The Geosat...
Topics: NASA Technical Reports Server (NTRS), COVARIANCE, ERROR ANALYSIS, GEOPOTENTIAL, GRAVITY ANOMALIES,...
End user concerns about the content and accessibility of libraries of remote sensing data in general are addressed. Recommendations pertaining to the United States' satellite remote sensing programs urge: (1) the continuation of the NASA/EROS Data Center program to convert pre-1979 scenes to computer readable tapes and create a historical archive of this valuable data; (2) improving the EROS archive by adding geologically interesting scenes, data from other agencies (including previously...
Topics: NASA Technical Reports Server (NTRS), AERIAL RECONNAISSANCE, DATA BASES, GEOLOGICAL SURVEYS, GEOSAT...
378
378
Sep 20, 2010
09/10
by
Rohrbach, A
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No Abstract Available
Topics: MAPS, GEOSAT SATELLITES, REMOTE SENSORS, TECHNOLOGY ASSESSMENT, TEXAS, URANIUM, UTAH, WEST...
A new method (constrained sinusoidal crossover adjustment) for removing the orbit error in satellite altimetry is tested (using crossovers accumulated in the first 91 days of the Geosat non-repeat era in the tropical Pacific) and found to have excellent qualities. Two features distinguish the new method from the conventional bias-and-tilt crossover adjustment. First, a sine wave (with wavelength equaling the circumference of the Earth) is used to represent the orbit error for each satellite...
Topics: NASA Technical Reports Server (NTRS), CROSSOVERS, ERROR ANALYSIS, GEOSAT SATELLITES, ORBITAL...
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243
Jun 9, 2011
06/11
by
Diskin, Glenn S.; Lempert, Walter R.; Miles, Richard B
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A three level model has been developed for the analysis of Schumann-Runge band (B(sup 3)Sigma(sup -)(sub u ) (- X(sup 3)Sigma(sup -)(sub g)) laser-induced fluorescence of molecular oxygen, O2. Such a model is required due to the severe lower state depletion which can occur when transitions having relatively large absorption cross-sections are excited. Such transitions are often utilized via ArF or KrF excimer or dye-laser excitation in high temperature environments. The rapid predissociation of...
Topics: TROPOSPHERE, CORRELATION COEFFICIENTS, SOUTHEAST ASIA, ANNUAL VARIATIONS, BIOMASS BURNING,...
This document is a compendium of the WFF GFO Software Development Team's knowledge regarding of GDO CAL/VAL Data. It includes many elements of a requirements document, a software specification document, a software design document, and a user's guide. In the more technical sections, this document assumes the reader is familiar with GFO and its CAL/VAL Data.
Topics: NASA Technical Reports Server (NTRS), GEOSAT SATELLITES, SOFTWARE ENGINEERING, PROGRAM VERIFICATION...
The central objective of this project has been the development of geostatistical methods fro mapping elevation and ice surface characteristics from satellite radar altimeter (RA) and Syntheitc Aperture Radar (SAR) data. The main results are an Atlas of elevation maps of Antarctica, from GEOSAT RA data and an Atlas from ERS-1 RA data, including a total of about 200 maps with 3 km grid resolution. Maps and digital terrain models are applied to monitor and study changes in Antarctic ice streams...
Topics: NASA Technical Reports Server (NTRS), ANTARCTIC REGIONS, SURFACE ROUGHNESS, TOPOGRAPHY, SYNTHETIC...
An attempt is made to determine the three-dimensional ocean circulation from satellite altimeter measurements by assimilating Geosat sea surface height data into an eddy-resolving QuasiGeostrophic (QG) model of the eastern North Atlantic Ocean. Results are tested against independent information from hydrographic field observations and moored current meter data collected during the Geosat ERM. The comparison supports the concept of inferring aspects of the three-dimensional flow field from sea...
Topics: NASA Technical Reports Server (NTRS), GEOSAT SATELLITES, DATA ACQUISITION, THREE DIMENSIONAL...
The most widely known modern method for estimating gravity field values from observed data is least-squares collocation. Its advantages are that it can make estimates at arbitrary locations based on irregularly spaced observations, and that it makes use of statistical information about errors in the input data while providing corresponding information about the quality of the output estimates. Disadvantages of collocation include the necessity of inverting square matrices of dimension equal to...
Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, APPROXIMATION, COLLOCATION, GRAVITATIONAL FIELDS,...
The purpose of this document is to present and document GFO performance analyses and results. This is the fifth Assessment Report since the initial report. This report extends the performance assessment since acceptance to 26 December 2005. The initial GFO Altimeter Engineering Assessment Report, March 2001 (NASA/TM-2001-209984/Ver.1/Vol.1) covered the GFO performance from Launch to Acceptance (10 February 1998 to 29 November 2000). The second of the series covered the performance from...
Topics: NASA Technical Reports Server (NTRS), ALTIMETERS, GEOSAT SATELLITES, ENGINEERING, INSTRUMENT...
The advantages of having Geosat Follow-On in a Geosat orbit flying simultaneously with Topex Follow-On in a Topex/Poseidon orbit are examined. The orbits are evaluated using two criteria. The first is the acute crossover angle. This angle should be at least 40 degrees in order to accurately resolve the slope of sea level at crossover locations. The second is tidal aliasing. In order to solve for tides, the largest constituents should not be aliased to a frequency lower than two cycles/year and...
Topics: NASA Technical Reports Server (NTRS), DATA SAMPLING, EARTH ORBITS, GEOSAT SATELLITES, SATELLITE...
The US Navy's GEOSAT Follow-On Spacecraft was launched on February 10, 1998 with the primary objective of the mission to map the oceans using a radar altimeter. Following an extensive set of calibration campaigns in 1999 and 2000, the US Navy formally accepted delivery of the satellite on November 29, 2000. Satellite laser ranging (SLR) and Doppler (Tranet-style) beacons track the spacecraft. Although limited amounts of GPS data were obtained, the primary mode of tracking remains satellite...
Topics: NASA Technical Reports Server (NTRS), ALTIMETERS, CROSSOVERS, ORBIT DETERMINATION, SATELLITE LASER...
In order to compare wind speed estimates from the Geosat altimeter and the Special Sensor Microwave/Imager (SSM/I), 25 colocated passes, within 2 hours of each other, were selected and the SSM/I estimates of wind speed and atmospheric parameters extracted along the Geosat track. Both instruments and their algorithms are described. A statistical comparison of wind speed estimates is presented and the effects of the atmospheric parameters from Geosat are analyzed. Quasi-simultaneous measurements...
Topics: NASA Technical Reports Server (NTRS), ALTIMETERS, ATMOSPHERIC SOUNDING, GEOSAT SATELLITES, MARINE...
The U.S. Navy's Geosat Follow-On (GFO) Mission, launched on February 20, 1998, is one of a series of altimetric satellites which include Seasat, Geosat, ERS-1, and TOPEX/POSEIDON (T/P). The purpose of this report is to document the GFO altimeter performance determined from the analyses and results performed by NASA's GSFC and Wallops altimeter, calibration team. It is the third of an anticipated series of NASA's GSFC and Wallops GFO performance documents, each of which will update assessment...
Topics: NASA Technical Reports Server (NTRS), ALTIMETERS, GEOSAT SATELLITES, NAVY, SEASAT SATELLITES,...
The ability of satellite-borne radar altimeter data to measure the global ocean surface with high precision and dense spatial coverage provides a unique tool for the mapping of the Earth's gravity field and its geoid. The altimeter crossover measurements, created by differencing direct altimeter measurements at the subsatellite points where the orbit ground tracks intersect, have the distinct advantage of eliminating geoid error and other nontemporal or long period oceanographic features. In...
Topics: NASA Technical Reports Server (NTRS), EARTH GRAVITATION, GEODETIC SURVEYS, GEOIDS, GRAVITATIONAL...
The improvement in the climatological behavior of a numerical model as a consequence of the assimilation of surface data is investigated. The model used for this study is a quasigeostrophic (QG) model of the Gulf Stream region. The data that have been assimilated are maps of sea surface height that have been obtained as the superposition of sea surface height variability deduced from the Geosat altimeter measurements and a mean field constructed from historical hydrographic data. The method...
Topics: NASA Technical Reports Server (NTRS), ALTIMETERS, ASSIMILATION, GULF STREAM, MATHEMATICAL MODELS,...
Mean changes in the surface elevation near the west margin of the Greenland ice sheet are measured using Seasat altimetry and altimetry from the Geosat Exact Repeat Mission (ERM). The Seasat data extend from early July through early October 1978. The ERM data extend from winter 1986-87 through fall 1988. Both seasonal and multi-year changes are measured using altimetry referenced to GEM T2 orbits. The possible effects of orbit error are minimized by adjusting the orbits into a common ocean...
Topics: NASA Technical Reports Server (NTRS), LAND ICE, ELEVATION, SATELLITE ALTIMETRY, RADIO ALTIMETERS,...
GEOSAT is a multi-technique geodetic analysis software developed at Forsvarets Forsknings Institutt (Norwegian defense research establishment). The Norwegian Mapping Authority has now installed the software and has, together with Forsvarets Forsknings Institutt, adapted the software to deliver datum-free normal equation systems in SINEX format. The goal is to be accepted as an IVS Associate Analysis Center and to provide contributions to the IVS EOP combination on a routine basis. GEOSAT is...
Topics: NASA Technical Reports Server (NTRS), VERY LONG BASE INTERFEROMETRY, GEOSAT SATELLITES,...
This final report summarizes activities conducted during the three years of the NASA High Resolution Microwave Survey (HRMS). With primary interest in the Sky Survey activity, the principal investigator attended nine Working Group meetings and traveled independently to conduct experiments or present results at other meetings. The major activity involved evaluating the effects of spaceborne radio frequency interference (RFI) on both the SETI sky survey and targeted search. The development of a...
Topics: NASA Technical Reports Server (NTRS), EXTRATERRESTRIAL INTELLIGENCE, MICROWAVE TRANSMISSION,...
Marine gravity surveying in polar regions was typically difficult and costly, requiring expensive long range research vessels and ice-breakers. Satellite altimetry can recover the gravity field in these regions where it is feasible to survey with a surface vessel. Unfortunately, the data collected by the first global altimetry mission, Seasat, was collected only during the austral winter, producing a very poor quality gravitational filed for the southern oceans, particularly in the...
Topics: NASA Technical Reports Server (NTRS), ANTARCTIC REGIONS, GRAVITATIONAL FIELDS, MAPPING, SATELLITE...
The Earth's modem climate change has been characterized by interlinked changes in temperature, CO2, ice sheets and sea level. Global sea level change is a critical indicator for study of contemporary climate change. Sea level rise appears to have accelerated since the ice sheet retreats have stopped some 5000 years ago and it is estimated that the sea level rise has been approx. 15 cm over the last century. Contemporary radar altimeters represent the only technique capable of monitoring global...
Topics: NASA Technical Reports Server (NTRS), CALIBRATING, CARBON DIOXIDE, CLIMATE CHANGE, ESTIMATING,...
We use the LaRC Lagrangian Chemistry and Transport Model (LCTM) [Considine et al., 2007; Pierce et al., 2003] to intercompare ACE, Aura, and HALOE observations of long-lived trace species. The LCTM calculates the transport, mixing, and photochemical evolution of an ensemble of parcels that have been initialized from ACE-FTS measurements. Here we focus on late November, 2004 comparisons, due to the previous 3-week period of continuous HALOE observations and MLS v2.2 data on November 29, 2004.
Topics: NASA Technical Reports Server (NTRS), HALOGEN OCCULTATION EXPERIMENT, LAGRANGIAN FUNCTION, TRACE...
If the geoid and the satellite position are known accurately, satellite altimetry can be used to determine the geostrophic velocity of the surface ocean currents. The purpose of this investigation is to simultaneously estimate the sea surface topography, zeta, the model for the gravity field, and the satellite orbit. Satellite tracking data from fourteen satellites were used; along with Seasat and Geosat altimeter data as well as surface gravity data for the solution. The estimated model of...
Topics: NASA Technical Reports Server (NTRS), EARTH GRAVITATION, GEOIDS, GRAVITATIONAL FIELDS, OCEAN...
Slant range analysis of radar altimeter data from the Seasat, Geosat, ERS-1 and ERS-2 databases are used to determine barrier location at particular times, and estimate barrier motion (km/yr) for major Antarctic ice shelves. The barrier locations, which are the seaward edges or fronts of floating ice shelves, advance with time as the ice flows from the grounded ice sheets and retreat whenever icebergs calve from the fronts. The analysis covers various multiyear intervals from 1978 to 1998,...
Topics: NASA Technical Reports Server (NTRS), ANTARCTIC REGIONS, DATA BASES, SLOPES, POSITION (LOCATION),...
The US Navy's GEOSAT Follow-On spacecraft (GFO) primary mission objective is to map the oceans using a radar altimeter. Satellite laser ranging data, especially in combination with altimeter crossover data, offer the only means of determining high-quality precise orbits. Two tuned gravity models, PGS7727 and PGS7777b, were created at NASA GSFC for GFO that reduce the predicted radial orbit through degree 70 to 13.7 and 10.0 mm. A macromodel was developed to model the nonconservative forces and...
Topics: NASA Technical Reports Server (NTRS), GEOSAT SATELLITES, RADIO ALTIMETERS, OCEANS, RANGEFINDING,...
Follow-on missions to provide continuity in the observation of the sea surface topography once the successful TOPEX/POSEIDON (T/P) oceanographic satellite mission has ended are discussed. Candidates include orbits which follow the ground tracks of T/P GEOSAT or ERS-1. The T/P precision ephemerides, estimated to be near 3 cm root-mean-square, demonstrate the radial orbit accuracy that can be achieved at 1300 km altitude. However, the radial orbit accuracy which can be achieved for a mission at...
Topics: NASA Technical Reports Server (NTRS), ALTIMETERS, EPHEMERIDES, GEOSAT SATELLITES, GLOBAL...
Satellite-based altimetric data taken by GOES-3, SEASAT, and GEOSAT over the Aral Sea, the Black Sea, and the Caspian Sea are analyzed and a least squares collocation technique is used to predict the geoid undulations on a 0.25x0.25 deg. grid and to transform these geoid undulations to free air gravity anomalies. Rapp's 180x180 geopotential model is used as the reference surface for the collocation procedure. The result of geoid to gravity transformation is, however, sensitive to the...
Topics: NASA Technical Reports Server (NTRS), COLLOCATION, GEOIDS, GEOPOTENTIAL, GRAVITY ANOMALIES,...
The U.S. Navy's Geosat Follow-On (GFO) Mission, launched February 10, 1998, is one of a series of altimetric satellites which include Seasat, Geosat, ERS-1, and TOPEX/POSEIDON (T/P). The purpose of this report is to document the GFO altimeter performance determined from the analyses and results performed by NASA's GSFC and Wallops altimeter calibration team. It is the fourth of an anticipated series of NASA's GSFC and Wallops GFO performance documents, each of which will update assessment...
Topics: NASA Technical Reports Server (NTRS), ALTIMETERS, GEOSAT SATELLITES, TOPOGRAPHY, ANNUAL VARIATIONS,...
