Shuttle Radar Topography Mission (SRTM) Non-Void Filled

The Shuttle Radar Topography Mission (SRTM) was flown aboard the space shuttle Endeavour February 11-22, 2000. The National Aeronautics and Space Administration (NASA) and the National Geospatial-Intelligence Agency (NGA) participated in an international project to acquire radar data which were used to create the first near-global set of land elevations. The radars used during the SRTM mission were actually developed and flown on two Endeavour missions in 1994. The C-band Spaceborne Imaging Radar and the X-Band Synthetic Aperture Radar (X-SAR) hardware were used on board the space shuttle in April and October 1994 to gather data about Earth's environment. The technology was modified for the SRTM mission to collect interferometric radar, which compared two radar images or signals taken at slightly different angles. This mission used single-pass interferometry, which acquired two signals at the same time by using two different radar antennas. An antenna located on board the space shuttle collected one data set and the other data set was collected by an antenna located at the end of a 60-meter mast that extended from the shuttle. Differences between the two signals allowed for the calculation of surface elevation. Endeavour orbited Earth 16 times each day during the 11-day mission, completing 176 orbits. SRTM successfully collected radar data over 80% of the Earth's land surface between 60 degree north and 56 degree south latitude with data points posted every 1 arc-second (approximately 30 meters).

航天雷达地形测绘任务（Shuttle Radar Topography Mission，简称SRTM）于2000年2月11日至22日由奋进号航天飞机搭载执行。美国国家航空航天局（National Aeronautics and Space Administration，简称NASA）与美国国家地理空间情报局（National Geospatial-Intelligence Agency，简称NGA）共同参与了这项国际项目，旨在获取雷达数据以制作全球首套近全域陆地高程数据集。本次任务使用的雷达系统实际早在1994年的两次奋进号任务中就已完成开发并搭载升空。1994年4月与10月，C波段星载成像雷达与X波段合成孔径雷达（X-Band Synthetic Aperture Radar，简称X-SAR）硬件搭载于航天飞机，用于采集地球环境相关数据。该技术针对SRTM任务进行了适配改造，以获取干涉雷达数据——即对比在略微不同观测角度下采集的两幅雷达图像或信号。本次任务采用单程干涉测量技术，通过两套不同的雷达天线同时采集两路信号：一套由航天飞机机身搭载的天线完成数据采集，另一套则由从机身伸出的60米长桅杆末端的天线获取。通过分析两路信号的差异，即可计算得到地表高程。在为期11天的任务中，奋进号每日绕地球飞行16圈，总计完成176次轨道运行。SRTM成功采集了北纬60度至南纬56度之间全球80%陆地表面的雷达数据，数据点间距为1角秒（约30米）。