Discoverer 25, also known as Corona 9017, was an American optical reconnaissance satellite which was launched in 1961. It was a KH-2 Corona' satellite, based on an Agena-B. The launch of Discoverer 25 occurred at 23:02 UTC on 16 June 1961. A Thor DM-21 Agena-B rocket was used, flying from Launch Complex 75-1-1 at the Vandenberg Air Force Base. Upon successfully reaching orbit, it was assigned the Harvard designation 1961 Xi 1.