NODC Standard Product: US Navy Geosat altimeter geophysical data records (GDRs) for the Geodetic Mission (NODC Accession 0053782)

This accession contains a complete copy of an NODC four CD-ROM product set containing all of NOAA's geophysical data records (GDRs) for the Geosat altimeter data obtained between March 30, 1985 and September 30, 1986 (the period known as Geosat's Geodetic Mission (GM)). This CD-ROM set supersedes a previous release of the Geodetic Mission GDRs, which was limited to the region south of 30 S. These data are in binary format.

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 application in areas of geodesy, geophysics, ocean dynamics, and global climate research.

The acronym Geosat was derived from geodetic satellite because its primary mission was to obtain a high-resolution description of the marine geoid. This goal was achieved during the first 18 months, known as the geodetic mission (GM), which extended from March 30, 1985 to September 30, 1986. The GM was based on a 23-day, near-repeat orbit which was permitted to drift, ultimately producing a tightly spaced ground track pattern. At the end of 18 months, the spacing between adjacent tracks at the equator was approximately 5 km, and at 60 degrees latitude only 2 or 3 km.

Because of their military significance, GM altimeter data were initially classified, but in 1992 the U.S. Navy approved the release of all GM altimetry in the latitude band 30 S to 72 S. In June, 1995, the remainder of the GM data were declassified by the Navy. This CD-ROM set contains NOAA's version of these declassified global GM GDRs. For a description of the content and format, refer to the Complete Geosat Altimeter GDR Handbook, Cheney et al. (1991b).