Crossover difference data records (XDR) from GEOSAT Geodetic Mission (GM) and Exact Repeat Mission (ERM) data from 01 April 1985 to 07 November 1987 (NCEI Accession 9100031)

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1985年4月1日至1987年11月7日期间，大地测量卫星GEOSAT的大地测量任务（Geodetic Mission, GM）与精确重复任务（Exact Repeat Mission, ERM）产生的交叉点差异数据记录（Crossover difference data records, XDRs）。数据集包含的参数有：时间、轨道、经纬度以及海面高度。数据校正项包括：海平面校正、风浪数据校正、潮汐校正、干/湿对流层校正、电离层校正、高度偏差校正、测高仪交叉点差异校正、测高仪海面测量校正以及航天器姿态校正。本数据集由美国海军通过国家海洋服务局（National Ocean Service）提交。

美国海军GEOSAT（大地测量卫星）雷达测高任务总持续时长近5年（1985年3月至1990年1月），在全球海洋范围内累计采集约7.5亿条海平面、浪高与风速测量数据。在大地测量任务阶段（1985年3月至1986年9月），卫星地面轨迹在整个任务周期内均无重复。1986年10月初，卫星轨道进行调整，以启动精确重复任务（ERM），该任务从1986年11月持续至1990年1月卫星停止运行。在ERM阶段，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，联合美国国家海洋和大气管理局/国家海洋服务局（NOAA/NOS）卫星测高小组完成处理。数据产品随后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，且该数据集目前存档于NODC。