Courtesy of Ted Molczan and the SEESAT-L newgroup:
The U.S. National Reconnaissance Office has declassified Project Quill. It resulted in the launch of an experimental synthetic aperture radar satellite in December 1964 (FTV 2355 / 1964-087A / 00964). The mission successfully proved the concept.
The declassified documents are available at http://www.nro.gov/foia/declass/QUILL.html