There have been several difficulties involved in spatially resolved
mid-infrared observing of Uranus. The technology for the requisite
pixel size in the detectors has not been available. This factor along
with the small angular diameter, 3.7
at opposition, has made it
difficult to observe Uranus as anything other than a disk-averaged
profile. Because of this all previous ground-based work has been
disk spectroscopy. Using
a new mid-infrared camera, I propose to accomplish the first
ground-based spatial imaging of Uranus.
The Mid-InfraRed Array Camera (MIRAC)
was designed for ground-based work in the 2, 3.8, 5,
8-14, and 17-24 
atmospheric windows (Hoffmann et al. 1993,
1994). In the past year the capabilities of this camera have been
expanded significantly by the installation of a new array with 
pixels, each 75 
across. The Rockwell HF16 Si:As
impurity-band conduction array gives a pixel scale of 0.37
. At
20 
this gives 3 resolution elements across the diameter with
a total of 7 on the disk.
The upgraded MIRAC was first used during the month set aside for observations of the Comet Shoemaker-Levy 9 impact with Jupiter at NASA's InfraRed Telescope Facility (IRTF). The proposer was part of the analysis team for this experiment, and as such has gained insights into the data reduction. Figure 1 shows a sample image reduced by the proposer. Up-to-date camera performance statistics have been provided by the camera designer, William Hoffmann, who is an enthusiastic collaborator on the project.
The IRTF was designed and optimized for infrared observing. This fact
combined with the large mirror size makes it the ideal facility.
Because of Uranus's low temperature and greater distance when compared
to Jupiter, observations at longer wavelengths are needed. Since the
facility instruments at IRTF are for near infrared, MIRAC is required
to access the 17-24 
band.
Noise sensitivity has been established from the comet impact project, allowing
calculations that show for
a signal-to-noise ratio of 20 per pixel, approximately
3 hours on target will be needed for one observation. This will
require 3 partial nights because the sky is an overwhelming emitter at
these wavelength, requiring telescope chopping and
nodding.
Support observations if necessary will be easily attainable at the 3.5 and 1 meter telescopes of nearby Apache Point Observatory, which is run by the Astrophysical Research Consortium, of which New Mexico State University is a member.