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

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Abstract
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.