Temperatures of Titan and the Galilean Satellites at 20 Microns

Abstract

Broad-band 20-M observations made at Mauna Kea in 1971 give the following effective temperatures in degrees K Titan 93 + 1; J 1,127 + 3; J 11,119 I 3; J III, 134 I 4; J IV, 149 I 5. The temperatures of the Galilean satellites are in fair agreement with observations at shorter wavelengths and with theory. The 20- flux of Titan is nearly an order of magnitude lower than expected, suggesting either low surface emissivity or high atmospheric opacity between 18 and 25 H2 could produce the required opacity, but the abundance needed is large.