We analyze two sets of observations Dione's co-orbital satellite Helene taken by Cassini's Composite Infrared Spectrometer (CIRS). The first observation was a CIRS FP3 (600 to 1100 cm−1, 9.1 16.7 μm) stare Helene's trailing hemisphere, where the ten pixels were filled. daytime surface temperatures derived from these 83.3 ± 0.9 K and 88.8 0.8 at local times 223° 288° 180° 238° respectively. When...