| Discoverer 25 | |
| Mission Type: | Optical reconnaissance |
| Operator: | US Air Force/NRO |
| Harvard Designation: | 1961 Xi 1 |
| Mission Duration: | 2 days |
| Spacecraft Type: | Corona KH-2 |
| Spacecraft Bus: | Agena-B |
| Manufacturer: | Lockheed |
| Launch Date: | UTC |
| Launch Rocket: | Thor DM-21 Agena-B 303 |
| Launch Site: | Vandenberg LC-75-1-1 |
| Orbit Reference: | Geocentric |
| Orbit Regime: | Low Earth |
| Orbit Periapsis: | 223km (139miles) |
| Orbit Apoapsis: | 361km (224miles) |
| Orbit Inclination: | 82.1 degrees |
| Orbit Period: | 90.4 minutes |
| Apsis: | gee |
| Programme: | Discoverer |
| Previous Mission: | Discoverer 22 |
| Next Mission: | Discoverer 26 |
| Programme2: | Corona KH-2 |
| Previous Mission2: | Corona 9015 |
| Next Mission2: | Corona 9019 |
Discoverer 25, also known as Corona 9017, was an American optical reconnaissance satellite which was launched in 1961. It was the fifth of ten Corona KH-2 satellites, based on the Agena-B.[1]
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.[2] Upon successfully reaching orbit, it was assigned the Harvard designation 1961 Xi 1.
Discoverer 25 was operated in a low Earth orbit, with a perigee of, an apogee of, 82.1 degrees of inclination, and a period of 90.4 minutes.[3] The satellite had a mass of,[4] and was equipped with a panoramic camera with a focal length of, which had a maximum resolution of .[5] Images were recorded onto 70mm film, and returned in a Satellite Recovery Vehicle two days after launch. The Satellite Recovery Vehicle used by Discoverer 25 was SRV-510. Once its images had been returned, Discoverer 25's mission was complete, and it remained in orbit until it decayed on 12 July 1961.[3]
The Satellite Recovery Vehicle was designed to be recovered in mid-air by a Fairchild C-119J Flying Boxcar aircraft. As SRV-510 descended, the C-119J was unable to capture it, and the capsule had to be recovered at sea after it landed. The film it returned was affected by streaks across images.[4]