Explorer 11 1205478 194007129 2008-02-25T20:42:07Z Van der Hoorn 292035 Added links '''Explorer 11''' (also known as S15) was the [[orbital spaceflight|orbital]] spacecraft that carried the first [[gamma ray]] [[telescope]]. This was the earliest beginnings of [[gamma-ray astronomy]]. Launched on [[April 27]], [[1961]] by a [[PGM-19 Jupiter|Juno II rocket]] the satellite returned data until early September, when power supply problems eventually ended the mission. During the spacecraft's four month lifespan it detected twenty-two events from gamma-rays and approximately 22,000 events from [[cosmic radiation]]. The telescope used a combination of a sandwich [[scintillator]] detector along with a [[Cherenkov]] counter to measure direction of events. Since the telescope could not be aimed the spacecraft was set in an end over end tumble to give a rough scan of the [[celestial sphere]], with emphasis on the [[galactic coordinate system|galactic plane]], the [[Galactic Center]], the [[Sun]], and other known [[radio]] noise sources. The gamma-ray events observed by Explorer 11 seemed to suggest a random distribution 'background' of gamma-rays. Later telescopes observed [[point source]]s in addition to the background noise of gamma-rays. == External links == * [http://library01.gsfc.nasa.gov/cgi-bin/gdprojs/searchAlpha.pl?letter=E Goddard Project Historical Missions] * [http://legacy.gsfc.nasa.gov/docs/heasarc/missions/explorer11.html Explorer 11] * [http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1961-013A S15] * [http://www.friends-partners.org/partners/mwade/lvs/junoii.htm Juno II] * [http://legacy.gsfc.nasa.gov/Images/explorer/explorer-11_small.gif GIF image] {{Explorer program}} [[Category:Explorer program]] [[Category:Observational astronomy]] [[Category:Spacecraft]] [[it:Explorer 11]]