InSb Heterodyne Receivers For Submillimeter Astronomy

InSb hot electron bolometer mixer receivers have been used for submillimeter line studies of the interstellar medium up to frequencies of about 500 GHz (600u). Detections of new interstellar lines have been made, such as the ground state fine structure transition of atomic carbon at 492 GHz, and various transitions of molecules such as carbon monoxide and water. The bulk of this work has been performed with the NASA Kuiper Airborne Observatory telescope which is transported to an altitude of aboutl2,000 km by a C141 aircraft, so avoiding most of the effects of the Earth's atmosphere. Some observations have also been made at ground observatories with the 5 m Hale telescope at Mount Palomar and the NASA In-frared Telescope Facility at Mauna Kea, Hawaii. The heterodyne bolometer receivers have achieved noise temperatures of less than 400 K at all frequencies up to 500 GHz. Develop-ment work continues to extend the frequency range further into the submillimeter band.