Pre-flight preparation of the Kuiper Airborne Observatory (KAO). This is a converted Lockheed C-141A Starlifter aircraft, operated by NASA since 1974. Its main instrument is a 90-cm infrared telescope. The KAO can cruise at up to 12,500 meters, well above most of the atmospheric water vapor that absorbs far infrared radiation and prevents ground-based far-IR astronomy. Here, the liquid nitrogen tanks in the rear of the aircraft are being filled, venting gas producing the cloud. Liquid nitrogen is used in the cryogenics system used to maintain the temperature of the KAO's instruments to within one degree of absolute zero (-273 Celsius). NASA AMES Research Center at Moffett Field, Mt. View, California.