Why not use commercial satellites to collect the data?
Optical satellites have problems collecting two clear images of many sites because of cloud cover and darkness. Currently operating radar satellites were not designed to collect this type of data. Critical information such as their exact location is not available. Ground control points can be used to get around some problems, but the SRTM required no ground control, which was an advantage in inaccessible regions. The use of the new technology of single-pass radar interferometry was experimental and involved some risk because it tested technologies never used before to measure the mast and shuttle attitude. But part of NASA’s charter is to experiment and test flight technologies in space for future use on commercial satellites or transfer to the commercial sector.
