Bhangmeter
A bhangmeter is a type of photometer used on reconnaissance satellites that is intended to detect atmospheric nuclear detonations.[1]
The first satellites which incorporated bhangmeters were the Advanced Vela satellites. An earlier generation of Vela satellites had been designed to detect nuclear explosions, but were not equipped with bhangmeters (they used X-ray sensors instead to detect an intense single pulse of X-rays).[2]
The silicon photodiode sensors are designed to detect the distinctive bright double pulse of light that is emitted from atmospheric nuclear weapons explosions. This signature is a short and intense flash lasting around 1 millisecond, followed by a second much more prolonged and less intense emission of light taking a fraction of a second to several seconds to build up. The effect occurs because the surface of the early fireball is quickly overtaken by the expanding atmospheric shock wave composed of ionised gas. Although it emits a considerable amount of light itself, it is opaque and prevents the far brighter fireball from shining through. As the shock wave expands, the amount of light it emits increases with its surface area. The effect is unambiguous below about 30 km altitude, but above this height a more ambiguous single pulse is produced.[3]
The name of the detector is a playful pun,[4] which was bestowed upon it by Fred Reines, one of the scientists working on the project. The name is derived from the Indian word "bhang", a locally grown variety of cannabis which is smoked or drunk to induce intoxicating effects, the joke being that one would have to be on drugs to believe the bhangmeter detectors would work properly. This is in contrast to a "bangmeter" one might associate with detection of nuclear explosions.[5]
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[edit] References
- ^ Bulletin of Science, Technology & Society. Pergamon Press. 1985. http://books.google.com/?id=GmUEAAAAIAAJ.
- ^ Gruntman, Mike (2004). Blazing the trail: the early history of spacecraft and rocketry. American Institute of Aeronautics and Astronautics, Inc.. ISBN 1-56347-705-X. http://books.google.com/?id=2XY9KXxF8OEC&printsec=frontcover#v=onepage&q
- ^ Angelo, Josepha A. Jr. (2004). Nuclear Technology. Greenwood Press. pp. 304–306. ISBN 1-57356-366-6. http://books.google.com/?id=ITfaP-xY3LsC&printsec=frontcover#v=onepage&q
- ^ Ogle, William E. (October 1985). "An account of the return to Nuclear Weapons testing by the United States after the test moratorium 1958-1961" (PDF). United States Department of Energy - NV 291. pp. footnote pg. 67. http://www.nv.doe.gov/library/publications/doenv291.aspx. Retrieved 18 December 2008.
- ^ "Declassified DOE documentation.". pp. See footnote, bottom of first page. http://www.nv.doe.gov/library/publications/historical/NV291/Prologue3Bhangmeter_Intervals_Output_Summary.pdf.
