Behavior of Titan's atmosphere during a total eclipse

During its emergence from the Saturnian shadow on June 28, 1980, Titan was observed simultaneously in the visible and IR ranges (6000-9000 A, and 11.8 and 20 microns). The eclipse observation indicates that thin-atmosphere models with a modest greenhouse effect are likely to be incorrect. A thin atmosphere of pure methane in equilibrium with an ice surface of methane is in marginal agreement with the present data, but improved VLA temperature measurements would be a crucial test of this model. Both the eclipse observation and VLA measurements agree with a nitrogen-dominant atmospheric model, as indicated by preliminary Voyager results.