Samos 4

{{Infobox spaceflight

| name = Samos 4

| image =

| image_caption =

| mission_type = Reconnaissance

| operator = US Air Force

| website =

| mission_duration = 15-30 days (planned)
Failed to orbit

| spacecraft_bus = Agena-B

| spacecraft_type = Samos-E5

| manufacturer =

| dry_mass =

| launch_mass =

| power =

| launch_date = {{start-date|22 November 1961, 20:45:47|timezone=yes}} UTC

| launch_rocket = Atlas LV-3A Agena-B 108D

| launch_site = Point Arguello LC-1-1

| launch_contractor =

| orbit_epoch = Planned

| orbit_reference = Geocentric

| orbit_regime = Sun-synchronous low Earth

| orbit_periapsis =

| orbit_apoapsis =

| orbit_inclination =

| orbit_period =

| apsis = gee

}}

File:Atlas_Agena_B_with_Samos_4_(Nov._22_1961)_1.jpg

Samos 4 was an American reconnaissance satellite which was lost in a launch failure in 1961.{{cite web|url=http://www.astronautix.com/craft/samos.htm|title=Samos|first=Mark|last=Wade|publisher=Encyclopedia Astronautica|accessdate=17 June 2010|url-status=dead|archiveurl=https://web.archive.org/web/20100116203857/http://astronautix.com/craft/samos.htm|archivedate=16 January 2010}} It was a film-return reconnaissance spacecraft, meaning that it returned images in a film capsule at the end of its mission. It was operated as part of the Samos programme. Samos 4 was the first of three Samos-E5 spacecraft to be launched; Samos-E5 satellites were based on an Agena-B, and carried a camera with a focal length of {{convert|1.67|m}}, and a resolution of {{convert|1.5|m}}.{{cite web|url=http://space.skyrocket.de/doc_sdat/samos-e5.htm|title=Samos E-5|first=Gunter|last=Krebs|publisher=Gunter's Space Page|accessdate=17 June 2010}}

The launch of Samos 4 occurred at 20:45:47 UTC on 22 November 1961. An Atlas LV-3A Agena-B rocket was used, flying from Launch Complex 1-1 at the Point Arguello Naval Air Station.{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|first=Jonathan|last=McDowell|author-link=Jonathan McDowell|publisher=Jonathan's Space Page|accessdate=17 June 2010}} Four minutes and four seconds into the flight, the rocket's first stage attitude control system malfunctioned, and control over the rocket's pitch was lost. The rest of the flight proceeded nominally, but, by the time the second stage ignited, it had pitched up by 160 degrees and was hence facing in the wrong direction. Its three-minute-41-second burn reduced the vehicle's velocity instead of increasing it, and as a result the satellite failed to achieve orbit.{{cite web|url=http://www.planet4589.org/space/book/programs/nro/usafnro/SAMOSPROGRAM101/1961-F13.html|title=SAMOS 4|work=The History of Spaceflight|first=Jonathan|last=McDowell|publisher=Jonathan's Space Page|accessdate=17 June 2010}} Samos 4 was to have operated in a Sun-synchronous low Earth orbit. It was designed to operate for between 15 and 30 days.