17.16-P
Occultation of U138 by Uranus' Rings
A.A. Sickafoose, A.S. Bosh (Lowell Obs.)
The occultation by Uranus of U138 (SAO 163583;
Klemola and Mink, 1991, Astron. J. 102, 389) was
observed on 10 April 1996 using the Faint Object
Spectrograph on the Hubble Space Telescope. The 
ring was observed on ingress, while 6, 5, 4, 
, 
, 
, 
,
, and 
were clearly detected during egress. One of
the strengths of this occultation observation is the
fact that it is spectrally resolved, including data
over a wavelength range of 3546 - 7080 
with
resolution 25 . The unusually high signal-to-
noise ratio of these data allows detection of
optically thin features normally hidden in the noise
as well as calculation of equivalent depths for at
least 140 different wavelength bins over this range.
We use these exceptional data to explore several
characteristics of the rings: the azimuthal
asymmetry of the ring, the particle size
distributions in all rings (via dependence of
equivalent depth on wavelength), and the structure
of the - and -ring shelves.