  Recent studies of stellar occultations observed by the Visual and Infrared
Mapping Spectrometer (VIMS) onboard the Cassini spacecraft have demonstrated
that multiple spiral wave structures in Saturn's rings are probably generated
by normal-mode oscillations inside the planet. Wavelet-based analyses have been
able to unambiguously determine both the number of spiral arms and the rotation
rate of many of these patterns. However, there are many more planetary normal
modes that should have resonances in the rings, implying that many normal modes
do not have sufficiently large amplitudes to generate obvious ring waves.
Fortunately, recent advances in wavelet analysis allow weaker wave signals to
be uncovered by combining data from multiple occultations. These new analytical
tools reveal that a pattern previously identified as a single spiral wave
actually consists of two superimposed waves, one with 5 spiral arms rotating at
1593.6 degrees/day and one with 11 spiral arms rotating at 1450.5 degrees/day.
Furthermore, a broad search for new waves revealed four previously unknown wave
patterns with 6, 7, 8 and 9 spiral arms rotating around the planet at 1538.2
degrees/day, 1492.5 degrees/day, 1454.2 degrees/day and 1421.8 degrees/day,
respectively. These six patterns provide precise frequencies for another six
fundamental normal modes inside Saturn, yielding what is now a complete
sequence of fundamental sectoral normal modes with azimuthal wavenumbers from 2
to 10. These frequencies should place strong constraints on Saturn's interior
structure and rotation rate, while the relative amplitudes of these waves
should help clarify how the corresponding normal modes are excited inside the
planet.
