This collection contains Sensor Data Records (SDRs), Geodetic Data Records (GDRs), Waveform Data Records (WDRs), and Crossover Difference data Records (XDRs) from the GEOSAT Geodetic Mission (GM) and Exact Repeat Mission (ERM) for the time period of March 30, 1985 to December 31, 1989. Parameters include: time, orbit, latitude/longitude, and sea surface height. Corrections to the data include: sea level, wind and wave data, tides, dry and wet troposphere, ionosphere, height bias, altimeter crossover differences, altimeter sea surface measurement, and spacecraft orientation. These data were submitted by the U.S. Navy via National Ocean Service. This collection also contains complete copies of four NODC Standard Products, including US Navy Geosat altimeter geophysical data records (GDRs) for the Geodetic Mission (4 CD-ROMs), US Navy Geosat wind/wave data (WWDR) from the Geodetic Mission (4 CD-ROMs), US Navy Geosat Enhanced JGM-3 Geophysical Data Records (GDR) from the Geodetic and Exact Repeat Missions (4 CD-ROMs), and US Navy Geosat altimeter Crossover Differences (XDRs) for the Geodetic Mission (8 CD-ROMs). The US Navy Geosat (Geodetic Satellite) radar altimeter mission lasted for nearly 5 years (March 1985 to January 1990) and collected approximately 750 million measurements of sea level, wave height, and wind speed over the global oceans. During the Geodetic Mission (March 1985 to September 1986), the satellite did not repeat its ground track for the duration of the mission. The orbit of the satellite was changed in early October 1986 to begin the Exact Repeat Mission (ERM) which lasted from November 8, 1986 until the satellite quit functioning in January 1990. During the ERM, the satellite repeated its ground track every 17 days. Data were initially processed by the Johns Hopkins University Applied Physics Laboratory in Laurel, MD in coordination with the NOAA/NOS Satellite Altimeter Group. Data products were transferred to the NOAA National Oceanographic Data Center (NODC) for distribution. Data products are archived at the NODC. From March 1985 until January 1990, the U.S. Navy satellite Geosat generated a new data set with unprecedented spatial and temporal coverage of the global oceans. Designed and built at the Johns Hopkins University Applied Physics Laboratory, Geosat carried a radar altimeter which produced profiles of sea level, wave height, and wind speed along the satellite ground track. Such records have applications in many areas of geodesy, ocean dynamics, and global climate research. Experience with GEOS-3 and Seasat in the 1970s had demonstrated the enormous potential of altimetry, but neither mission provided such complete long-term global coverage. Geosat was launched on March 12, 1985, and altimeter data collection began on March 30. The acronym Geosat was derived from geodetic satellite, because its primary mission was to obtain a high-resolution description of the marine geoid up to latitudes of 72 degrees. This goal was achieved during the first 18 months, known as the Geodetic Mission (GM). During this time the ground track had a near-repeat period of about 23 days (330 revolutions in 23.07 days; average orbital period of 6039.84 sec). The drifting orbit resulted in a dense, global network of sea level profiles separated by about 4 km at the equator. Because of the military significance of this unique set of observations, the GM data were initially classified but in 1995 were released to NOAA in their entirety for public distribution. At the conclusion of the GM on September 30, 1986, the satellite orbit was changed, and the Exact Repeat Mission (ERM) began on November 8, 1986. This produced sea level profiles along tracks that repeated themselves within 1-2 km at intervals of about 17 days (244 revolutions in 17.05 days; average orbital period of 6037.55 sec). The ERM covered 62 complete 17-day cycles before tape recorder failure in October 1989 terminated the global data set. A limited amount of data was subsequently collected by direct broadcast in the North Atlantic and Gulf of Mexico. By January 1990 continued degradation of the altimeter output power finally ended the Geosat mission.

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NOAA_NCEI Short Name: gov.noaa.nodc:GEOSAT-GM-ERM Version ID: Not Applicable Unique ID: C2089386345-NOAA_NCEI

Southern Greenland ice sheet elevation change estimates are derived from SEASAT and GEOSAT radar altimetry data from 1978 to 1988. Data are confined to 61-72 deg N, 30-50 deg W, above 1700 m elevation. The addition of GEOSAT Geodetic Mission (GM) data results in twice as many crossover points and 50% greater coverage than previous studies. Coverage above 2000 m elevation is improved to 90%, and about 75% of the area between 1700 m and 2000 m is now covered. Data are in ASCII text format, available via FTP, and consist of elevation change rate (dH/dt, cm/year) and corresponding error estimates in 50 km grid cells.

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NSIDCV0 Short Name: NSIDC-0223 Version ID: 1 Unique ID: C1386204165-NSIDCV0

Gravity models are powerful tools for mapping tectonic structures, especially in the deep ocean basins where the topography remains unmapped by ships or is buried by thick sediment. We combined new radar altimeter measurements from satellites CryoSat-2 and Jason-1 with existing data to construct a global marine gravity model that is two times more accurate than previous models. We found an extinct spreading ridge in the Gulf of Mexico, a major propagating rift in the South Atlantic Ocean, abyssal hill fabric on slow-spreading ridges, and thousands of previously uncharted seamounts. These discoveries allow us to understand regional tectonic processes and highlight the importance of satellite-derived gravity models as one of the primary tools for the investigation of remote ocean basins.

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NOAA_NCEI Short Name: gov.noaa.nodc:0150966 Version ID: Not Applicable Unique ID: C2089379220-NOAA_NCEI

A Digital Elevation Model (DEM), ice thickness grid, and bedrock elevation grid of Greenland, acquired as part of the PARCA program. DEM data are a combination of ERS-1 and Geosat satellite radar altimetry data, Airborne Topographic Mapper (ATM) data, and photogrammetric digital height data. Ice thickness data are based on approximately 700,000 data points collected in the 1990s from a University of Kansas airborne Ice Penetrating Radar (IPR). Nearly 30,000 data points were collected in the 1970s from a Technical University of Denmark (TUD) airborne echo sounder.The ice thickness grid was subtracted from the DEM to produce a grid of bedrock elevation values. Data set applications include studies of gravitational driving stress and ice volume (mass balance) of the Greenland Ice Sheet.

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NSIDCV0 Short Name: NSIDC-0092 Version ID: 1 Unique ID: C1386250156-NSIDCV0

The sea surface topography (SSTop) spherical harmonic model, being complete through degree and order 10, has a spatial half wavelength resolution of 2000 km. It is derived in a joint orbit/gravity/SSTop solution (GRIM4-C3T) exploiting GEOSAT (doppler- and) altimeter data of observation period 1986, Dec. 14-31. The overall standard deviation is estimated to be about 15 cm. Satellite tracking data of 30 satellites and 10x10 mean gravity anomalies have been exploited along with the altimeter data for the complete solution.

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SCIOPS Short Name: GFZ-GRIM4_C3T_SSTOP Version ID: Not provided Unique ID: C1214585782-SCIOPS