The STS-38 mission of the Space Shuttle Atlantis was a classified mission conducted by NASA for the United States Department of Defense. STS-38's specific objectives and payload details remain classified. However, it's widely believed that the mission involved deploying or retrieving reconnaissance satellites, conducting experiments related to national security, or testing new technologies for military applications.

The second-generation Quasar satellites, also known as SDS-2, continue the legacy of the Satellite Data System (SDS) developed by the United States Air Force. Serving as communication relays, these satellites transmit real-time data from US reconnaissance satellites and support communication needs for USAF aircraft and ground stations. Operating in similar elliptical orbits for polar coverage, they maintain communication with KH-11 satellites using a 60 GHz frequency payload. Launched after the first-generation satellites, the SDS-2 series likely incorporates advancements in technology and may feature enhancements in capabilities such as improved data transmission rates or additional onboard systems.

Prowler is a secretive geostationary satellite allegedly deployed by Space Shuttle Atlantis (STS 38). It lacks an official designation but is identified by observers as 2000-653A / 90007. Based on the Hughes HS-376 bus, it likely served in satellite inspection or ELINT missions near Russian communication satellites' orbits. Prowler's stealth feature made it challenging to observe, and post-mission brightness changes suggest alterations to its orientation.