Ted Molczan recently completed research into the identity of an unknown GEO objects, 2000-653A /90007 - discovered by Ed Cannon in 1998. Ted concluded that it is a highly classified U.S. satellite called Prowler. The abstract and URL of the report on his findings follow.
Ted wrote on the SESSAT-L newsgroup: "Space Shuttle mission STS 38 is officially acknowledged to have deployed only a single payload, which is known to be a geosynchronous communications satellite, operated by the National Reconnaissance Office. It has since leaked out that STS 38 deployed a second payload: an optically
stealthy, geosynchronous satellite inspector, named Prowler.
"In 1998, hobbyists discovered a bright unknown GEO object, with optical and orbital characteristics of a satellite, which they call 2000-653A / 90007. By early 2010, independent GEO satellite observation networks had accounted for every single GEO satellite acknowledged to have been launched, yet 2000-653A remained unidentified. Analysis of its optical and orbital characteristics, and other relevant facts, reveals great consistency with the emerging Prowler story, resulting in a strong circumstantial case that 2000-653A is Prowler."
You can read Ted's complete report at http://satobs.org/seesat_ref/STS_38/Unknown_GEO_Object_2000-653A_-_90007_Identified_as_Prowler.pdf