Rocket-borne liquid helium cooled telescope.

We describe a rocket-borne telescope in which all components in or near the detector's field of view are cooled to liquid helium temperature. The system uses ir detectors to make photometric observations of the night sky in the 5-mu to ~1.6 mm spectral range. A description of the detectors and their calibration is given. On 29 February 1968, the telescope was successfully flown to an altitude of 170 km on an Aerobee 150 sounding rocket.