Voyager ultraviolet stellar occultation measurements of the composition and thermal profiles of the Saturnian upper atmosphere

Occultation of the star δ‐Scorpii by Saturn as recorded by the Voyager Ultraviolet Spectrometer yields the value of the exospheric temperature in the equatorial region to be 800 (+150, −120) K at an altitude of 1540 km above the 1‐bar atmospheric pressure level; the H2‐density at 1540 km is determined to be 5 (+3.6, −1.8) × 109 cm−3. Temperature gradient in the thermosphere is found to be 1.25 (+0.05, −0.07) K km−1. Methane volume mixing ratio at 965 km above the 1‐bar pressure level is determined to be 1.5 × 10−4.