Discoverer 28

Discoverer 28, also known as Corona 9021, was an American optical reconnaissance satellite which was lost in a launch failure in 1961. It was the last KH-2 Corona' satellite, which was based on an Agena-B.

The launch of Discoverer 28 occurred at 00:01 UTC on 4 August 1961. A Thor DM-21 Agena-B rocket was used, flying from Launch Complex 75-1-1 at the Vandenberg Air Force Base. It failed to achieve orbit after the Agena's guidance and control system malfunctioned.

Discoverer 28 was to have operated in a low Earth orbit. The satellite had a mass of 1150 kg, and was equipped with a panoramic camera with a focal length of 61 cm, which had a maximum resolution of 7.6 m. Images were to have been recorded onto 70 mm film, and returned in a Satellite Recovery Vehicle. The Satellite Recovery Vehicle carried by Discoverer 28 was SRV-512.