The Ring System of Uranus: Flat as a Pancake, Sprinkled with Dust Page: 8 of 33
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provide the most relevant AO parameters. Photometric calibrations were performed on
star HD201941 (Elias et al. 1982). From these observations we derived a conversion factor
of 3.1 x 10-4 with which to multiply the observed number of counts/sec/pixel to arrive at
the I/F per pixel. I is the observed intensity and rF is the solar flux density as reflected
from Uranus at K'.
Relevant ring parameters for the days that we observed are summarized in Table 2. On
each half night we observed Uranus typically three times, where each observation usually
consists of three sets of images, each integrated over 2 minutes. To obtain high signal-to-
noise images of Uranus' rings, we carefully aligned all images and then combined all data.
The total integration time on source is approximately 1.5 hrs. This process, of course,
smears out any atmospheric features, such as those seen in Fig. 1, as well as satellites.
Results of our final image are shown in Fig. 2. In panel a we show the image in its entirety,
and panels b and c show enlarged views of the two ring ansae. These images clearly reveal
the individual a, 0 and 6, 'y, rings, interior to the bright e ring. Rings 4,5,6 cannot be
resolved individually, but show up as an extended feature. Finally, interior to the 4,5,6
rings is a sheet of material which we believe is the ring 1986U2R, discovered by Voyager
2 in 1986 (Smith et al. 1986). Little is known about this ring; only one image of it was
taken with Voyager, at a phase angle of 90. The ring apparently has never even received
a proper name; in this paper we refer to this ring as the ( ring.
3. Image Analysis
3.1 Ring Models
In order to derive the I/F for the individual ringlets we need to either deconvolve the
data, or build a model that, after convolution with the PSF, does match the observations.
As in de Pater et al. (2002), we constructed models to fit the data by using both a 1D and
2D technique. In the 2D model, each of the 9 known rings (e, 6, y, il, 0, a, 4, 5 and 6)ci
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de Pater, I; Gibbard, S G & Hammel, H B. The Ring System of Uranus: Flat as a Pancake, Sprinkled with Dust, article, February 2, 2005; Livermore, California. (https://digital.library.unt.edu/ark:/67531/metadc876067/m1/8/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.