Thermal investigation of a large lunar telescope

Recent interest in construction of a large telescope on the lunar surface (Nein and Davis, 1991; Bely, Burrows, and Illingworth, 1989) has prompted this feasibility study of a thermal control system for a 16 meter diameter telescope located near the lunar equator. In addition to detailed analyses for a telescope located in a flat area near the equator, the thermal effect of locating the telescope in a crater, on a hill, and at higher latitude sites is discussed. Because an unprotected telescope experiences a wide range of temperature swings, several thermal protection schemes have been examined, including domes, sunshades, and ground shields to limit the temperature excursions of the primary mirror. Results of these analyses indicate that mirror temperature excursions can be limited to less than 100 Kelvin (K) per lunar cycle with an appropriate passive thermal protection system (dome), and that the telescope primary mirror can be maintained at less than 100 K for at least 7 days of each lunar cycle. However, such a dome precludes observations during the lunar day. Mirror temperature excursions can be reduced by incorporating thermal enclosures or shades in the design or by placing the telescope at a higher latitude.