PETER MENZEL / SCIENCE PHOTO LIBRARY PETER MENZEL / SCIENCE PHOTO LIBRARY
Airborne infrared astronomy. Technicians cooling the instruments of the Kuiper Airborne Observatory (KAO) infrared telescope, prior to flight. The KAO is a converted Lockheed C-141A Starlifter aircraft, equipped with a 90-cm infrared telescope. The instruments have to be cooled to within a fraction of a degree of absolute zero (minus 273 Celsius). This is achieved by using liquid helium inside a liquid nitrogen cryostat. Here the cold gas venting from the system is causing clouds of water vapour to condense from the air. The KAO cruises at up to 12,500 metres, well above most of the atmospheric water vapour which prevents ground-based far-IR astronomy.
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