Crossover difference data records (XDR) from GEOSAT Geodetic Mission (GM) and Exact Repeat Mission (ERM) data from 01 April 1985 to 07 November 1987 (NODC Accession 9000213)

Crossover difference data records (XDRs) from the GEOSAT Geodetic Mission (GM) and Exact Repeat Mission (ERM) for the time period of April 1, 1985 to November 7, 1987. 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.

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 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.

本数据集收录了1985年4月1日至1987年11月7日期间，大地测量卫星（GEOSAT）大地测量任务（Geodetic Mission, GM）与精确重复轨道任务（Exact Repeat Mission, ERM）产生的交叉点差分数据记录（Crossover Difference Data Records, XDRs）。其包含的参数包括：时间、轨道、经纬度与海面高度。数据校正项涵盖：海平面数据、风浪资料、潮汐、干对流层与湿对流层校正、电离层校正、高度偏差、高度计交叉点差分、高度计海面测量值以及航天器姿态。本数据集由美国海军通过美国国家海洋服务局（National Ocean Service, NOS）提交。

美国海军GEOSAT（大地测量卫星）雷达高度计任务总时长近5年（1985年3月至1990年1月），在全球海洋范围内采集了约7.5亿次海平面、浪高及风速的测量数据。在大地测量任务阶段（1985年3月至1986年9月），卫星在轨期间未重复地面轨迹。1986年10月初，卫星轨道完成调整，正式启动精确重复轨道任务（ERM），该任务从1986年11月持续至1990年1月卫星失效。在ERM阶段，卫星每17天重复一次地面轨迹。数据最初由马里兰州劳雷尔市的约翰·霍普金斯大学应用物理实验室，与美国国家海洋和大气管理局/国家海洋服务局（NOAA/NOS）卫星高度计小组协作处理。数据产品被移交至美国国家海洋和大气管理局国家海洋数据中心（National Oceanographic Data Center, NODC）进行分发，且所有数据产品均存档于NODC。