Since the invention of the Shuttle Imaging Radar (SIR), CERS has been using such images for archaeological exploration.  The initial images came from a shuttle flight in 1981 (SIR-A), while others were taken by two flights in 1994 (SIR-C). Numerous shuttle passes over western China resulted in images covering large tracts of southern Xinjiang. NASA has made these images available to CERS for analysis and future application in identifying lost settlements along the ancient Silk Road.