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).本归档数据集包含美国国家海洋数据中心（NODC）出品的四片装光盘套件的完整副本，该套件囊括了1985年3月30日至1986年9月30日期间获取的Geosat卫星高度计数据的所有地球物理数据记录（Geophysical Data Records，GDRs），此时间段即为Geosat的大地测量任务（Geodetic Mission，GM）周期。本光盘套件替代了此前发布的大地测量任务GDRs数据集，该早期数据集仅覆盖南纬30度以南区域。本次提供的数据均采用二进制格式存储。 1985年3月至1990年1月期间，美国海军的Geosat卫星采集了一套全新的数据集，其空间与时间覆盖范围在全球海洋领域均属空前。该卫星由约翰·霍普金斯大学应用物理实验室设计制造，搭载了雷达高度计，可沿卫星地面轨迹获取海平面、浪高以及风速的剖面数据。此类记录可应用于大地测量学、地球物理学、海洋动力学及全球气候研究等领域。 Geosat这一缩写源自"大地测量卫星（geodetic satellite）"，因其核心任务是获取高精度的海洋大地水准面描述数据。这一目标在任务最初的18个月内得以实现，也就是1985年3月30日至1986年9月30日的大地测量任务（GM）周期。大地测量任务采用为期23天的近重复轨道，轨道允许缓慢漂移，最终形成了间距极密的地面轨迹分布模式。在18个月任务末期，赤道区域相邻轨道的间距约为5公里，而在纬度60度处仅为2至3公里。 鉴于其军事价值，大地测量任务的高度计数据最初处于保密状态，但1992年美国海军批准公开南纬30度至72度区间内的全部GM高度计数据。1995年6月，美国海军将剩余的GM数据全部解密。本光盘套件包含美国国家海洋和大气管理局（NOAA）整理发布的上述解密全球GM GDRs数据集。如需了解数据内容与格式的详细说明，请参阅《完整Geosat高度计GDR手册》（Cheney等，1991b）。