Discoverer 33

{{short description|Reconnaissance satellite}}

{{Infobox spaceflight

| name = Discoverer 33

| image = KH-2_CORONA.jpg

| image_caption =

| mission_type = Optical reconnaissance

| operator = US Air Force/NRO

| mission_duration = Failed to orbit

| spacecraft =

| spacecraft_type = Corona KH-2

| spacecraft_bus = Agena-B

| manufacturer = Lockheed

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

| launch_date = {{start-date|23 October 1961, 19:23|timezone=yes}} UTC

| launch_rocket = Thor DM-21 Agena-B 329

| launch_site = Vandenberg LC-75-3-5

| orbit_epoch = Planned

| orbit_reference = Geocentric

| orbit_regime = Low Earth

| orbit_periapsis =

| orbit_apoapsis =

| orbit_inclination =

| orbit_period =

| apsis = gee

| programme = Discoverer

| previous_mission = Discoverer 32

| next_mission = Discoverer 34

| programme2 = Corona KH-2

| previous_mission2 = Corona 9021

| next_mission2 = Corona 9027

}}

Discoverer 33, also known as Corona 9026, was an American optical reconnaissance satellite which was lost in a launch failure in 1961. It was the eighth 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 33 occurred at 19:23 UTC on 23 October 1961. A Thor DM-21 Agena-B rocket was used, flying from Launch Complex 75-3-5 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=30 June 2010}} The launch was nominal through the Thor burn. Agena hydraulic system performance was erratic and resulted in numerous unplanned pitch and yaw maneuvers which drove the stage into an excessively lofted trajectory. At T+312 seconds hydraulic pressure was lost and the Agena began tumbling. The propulsion system shut down at T+322 seconds and the Agena fell into the Pacific. Following three occurrences of this failure mode in seven months, an extensive effort was made to redesign the Agena hydraulic system, improve weak points, and ensure that all systems were free of contamination.{{cite web|url=http://www.fas.org/spp/military/program/imint/kh-3.htm|title=KH-3 Corona|first=Christina|last=Lindborg|first2=John|last2=Pike|date=9 September 2000|accessdate=30 June 2010|publisher=Federation of American Scientists}}

Discoverer 33 was intended to have operated in a low Earth orbit. It had a mass of {{convert|1150|kg}},{{cite web|url=http://www.astronautix.com/craft/kh3.htm|title=KH-3|first=Mark|last=Wade|publisher=Encyclopedia Astronautica|accessdate=30 June 2010|url-status=dead|archiveurl=https://web.archive.org/web/20100918005311/http://astronautix.com/craft/kh3.htm|archivedate=18 September 2010}} 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=30 June 2010|url-status=dead|archiveurl=https://web.archive.org/web/20071003082210/http://msl.jpl.nasa.gov/Programs/corona.html|archivedate=3 October 2007}} It would have recorded images onto {{convert|70|mm|adj=on|sp=us}} film, and returned this in a Satellite Recovery Vehicle at the end of its mission. The Satellite Recovery Vehicle carried by Discoverer 33 was SRV-553.

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