With this subtitle to their 1962 "Gamman Ray Astronomy" article in Scientific American, William L. Kraushaar and George W. Clark announced to the world the start of gamma-ray astronomy from Earth-orbiting satellites. Explorer 11 was the first gamma-ray detection satellite flown, weighing in at 82 pounds. It was launched on 27 April 1961 and the instrument aboard was designed to detect gamma rays above 50 MeV. The satellite operated well until early September, when power supply problems became noticeable. Useful data ceased soon thereafter.
The satellite could not be actively pointed, and so, was put into a tumble in order to get a "rough" scan of the entire celestial sphere. By 19 May 1961, the satellite, located between 300 and 1100 miles above the Earth, began to send sky survey data to the ground. Over the next 4 months, it provided "nearly 20 miles of data on microfilm". Reconstruction of the data allowed gamma-ray times of arrival to be determined to 0.1 second, and where the detector was pointed to about 5 degrees.
Images of both the gamma-ray detector and schematics of its design are included in the Explorer-11 images page.
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