主题：【文摘】为了我们将来不吃JDAM 严防外国间谍测绘我国地形 -- 李根

一般卫星没有航天飞机那么大的尺寸和能量源，很难完成全球三维地形图这样的任务。

航天飞机说穿了就是个军用仪器。老美总是把它打扮成和平鸽，做点小科学试验给大家看，也算是一种欺世盗名。

看看这个网页：

http://mac.usgs.gov/isb/pubs/factsheets/fs07103.html

Under an agreement with the National Aeronautics and Space Administration (NASA) and the Department of Defense's National Geospatial-Intelligence Agency (NGA), the U.S. Geological Survey (USGS) is now distributing elevation data from the Shuttle Radar Topography Mission (SRTM). The SRTM is a joint project between NASA and NGA to map the Earth's land surface in three dimensions at a level of detail unprecedented for such a large area. Flown aboard the NASA Space Shuttle Endeavour February 11-22, 2000, the SRTM successfully collected data over 80 percent of the Earth's land surface, for most of the area between 60N. and 56S. latitude. The SRTM hardware included the Spaceborne Imaging Radar-C (SIR-C) and X-band Synthetic Aperture Radar (X-SAR) systems that had flown twice previously on other space shuttle missions. The SRTM data were collected specifically with a technique known as interferometry that allows image data from dual radar antennas to be processed for the extraction of ground heights.

Data

NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., processed more than 12 terabytes of raw SRTM data into preliminary, research-quality digital elevation models, on a continent-by-continent basis. NGA will complete editing, verification, and reformatting of the preliminary data by the end of September 2004. The USGS EROS Data Center in Sioux Falls, S. Dak., is the long-term archive for SRTM data and provides these data to the general public and the science community. Data available to the geospatial data user community include 1-arc-second (approximately 30-meter) resolution data over the United States and its territories, and 3-arc-second (approximately 90-meter) data over non-U.S. territory.The SRTM data complement other elevation data available from the USGS EROS Data Center.