Geodetic data records (GDRs) from the GEOSAT Exact Repeat Mission (ERM) from 31 October 1989 to 31 December 1989 (NODC Accession 9000022)

This accession contains one month of geodetic data records (GDRs) from the GEOSAT Exact Repeat Mission (ERM) for the time period of October 31, 1989 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 Oceanic Service.

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.

本数据集包含1989年10月31日至1989年12月31日期间，GEOSAT精确重复任务（Exact Repeat Mission, ERM）产出的一个月大地测量数据记录（Geodetic Data Records, GDRs）。其包含的参数涵盖时间、轨道、经纬度与海面高度。该数据集的数据校正项包括：海平面修正、风浪数据修正、潮汐修正、干对流层修正、湿对流层修正、电离层修正、高度偏差修正、高度计交叉轨迹差修正、高度计海面测量修正以及航天器姿态修正。此类数据由美国海军通过国家海洋服务局（National Oceanic Service）提交。

美国海军的GEOSAT（大地测量卫星，Geodetic Satellite）雷达高度计任务总持续时长近5年（1985年3月至1990年1月），在全球海洋范围内采集了约7.5亿条海平面、浪高及风速测量数据。在大地测量任务阶段（1985年3月至1986年9月），该卫星在任务全程内未重复其地面轨迹。1986年10月初，该卫星轨道完成调整，由此开启精确重复任务（ERM），该任务从1986年11月8日持续至1990年1月卫星失效为止。在精确重复任务阶段，该卫星每17天重复一次地面轨迹。数据最初由位于马里兰州劳雷尔市的约翰·霍普金斯大学应用物理实验室（Johns Hopkins University Applied Physics Laboratory）与NOAA/NOS卫星高度计小组协作处理。数据产品随后被移交至美国国家海洋和大气管理局国家海洋数据中心（NOAA National Oceanographic Data Center, NODC）进行分发，所有数据产品均存档于该中心。