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Abstract :
[en] Cassini’s Ultraviolet Imaging Spectrograph (UVIS) has completed five
years of study of Saturn’s atmosphere and auroras. Two long slit spectral channels are
used to obtain EUV data from 56.3-118.2 nm and FUV data from 111.5-191.3 nm. 64
spatial pixels along each slit are combined with slit motion to construct spectral images of
Saturn. Auroral emissions are seen from electron-excited molecular and atomic hydrogen.
In 2008-2009 UVIS obtained data with the spacecraft well out of Saturn’s ring plane,
permitting UVIS to obtain a number of short movies of the rotating auroral structures.
In some movies a cusp-like feature is present near noon inside the oval. One movie from
2008 day 201 shows parallel linear features on the day side almost at right angles to
the main auroral oval that appear, then lengthen, separate in the middle, and then fade
away. The same movie also shows one bright "polar flare" inside the oval. A few of
the most recent images were obtained at sufficiently close range that 2 spacecraft slews
were needed to completely cover the oval. These images provide almost 100 pixels of
information across the oval and clearly show multiple arcs of emission on the main oval
and scattered emissions inside the oval. We will discuss these features, their locations, and
possible interpretations. We also report on a search for an Enceladus auroral footprint
on Saturn.
