Discoverer 25

{{short description|Reconnaissance satellite}}

{{Infobox spaceflight

| name = Discoverer 25

| image = KH-2_CORONA.jpg

| image_caption =

| mission_type = Optical reconnaissance

| operator = US Air Force/NRO

| Harvard_designation = 1961 Xi 1

| SATCAT =

| mission_duration = 2 days

| spacecraft =

| spacecraft_type = Corona KH-2

| spacecraft_bus = Agena-B

| manufacturer = Lockheed

| launch_mass = {{convert|1150|kg}}

| launch_date = {{start-date|16 June 1961, 23:02:52|timezone=yes}} UTC

| launch_rocket = Thor DM-21 Agena-B 303

| launch_site = Vandenberg LC-75-1-1

| decay_date = {{end-date|12 July 1961}}

| landing_date =

| landing_site =

| orbit_epoch =

| orbit_reference = Geocentric

| orbit_regime = Low Earth

| orbit_periapsis = {{convert|223|km|mi|sp=us}}

| orbit_apoapsis = {{convert|361|km|mi|sp=us}}

| 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.{{cite web|url=https://space.skyrocket.de/doc_sdat/kh-2.htm|title=KH-2 Corona|first=Gunter|last=Krebs|publisher=Gunter's Space Page|accessdate=23 October 2020}}

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.{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|first=Jonathan|last=McDowell|publisher=Jonathan's Space Page|accessdate=26 June 2010}} 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 {{convert|223|km}}, an apogee of {{convert|361|km}}, 82.1 degrees of inclination, and a period of 90.4 minutes.{{cite web|url=http://planet4589.org/space/log/satcat.txt|title=Satellite Catalog|first=Jonathan|last=McDowell|author-link=Jonathan McDowell|publisher=Jonathan's Space Page|accessdate=26 June 2010}} The satellite had a mass of {{convert|1150|kg}},{{cite web|url=http://www.astronautix.com/craft/kh2.htm|title=KH-2|first=Mark|last=Wade|publisher=Encyclopedia Astronautica|accessdate=26 June 2010|url-status=dead|archiveurl=https://web.archive.org/web/20121023094149/http://www.astronautix.com/craft/kh2.htm|archivedate=23 October 2012}} and was equipped with a panoramic camera with a focal length of {{convert|61|cm}}, which had a maximum resolution of {{convert|7.6|m}}.{{cite web|url=http://msl.jpl.nasa.gov/programs/corona.html|title=Corona|publisher=NASA|work=Mission and Spacecraft Library|accessdate=26 June 2010|url-status=dead|archiveurl=https://web.archive.org/web/20071003082210/http://msl.jpl.nasa.gov/Programs/corona.html|archivedate=3 October 2007}} Images were recorded onto {{convert|70|mm|adj=on|sp=us}} 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.

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.