| Launch date | 1961-04-27 |
|---|---|
| Launch vehicle | Juno II rocket |
| Mission duration | ~7 months |
| Home page | http://heasarc.gsfc.nasa.gov/docs/heasarc/missions/explorer11.html |
| Mass | 37.2 kg or 82 lb[1] |
| Instruments | |
| Main instruments | Gamma ray telescope |
Explorer 11 (also known as S15) was the 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 Juno II rocket the satellite returned data until November 17, when power supply problems ended the science mission. During the spacecraft's seven month lifespan it detected twenty-two events from gamma-rays and approximately 22,000 events from cosmic radiation.
Instruments
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 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 sources in addition to the background noise of gamma-rays.
External links
References
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