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D. Lofton, N.J. Chanover, R.F. Beebe, M. Vincent (New Mexico State University), G.S. Orton, B. Fisher, P. Yanamandra-Fisher (JPL)
A monitoring program of Jupiter in support of NASA's Galileo mission began at NASA's Infrared Telescope Facility (IRTF) in 1995 and continues to the present time. Through this observing program, images of Jupiter are obtained at several near-infrared wavelengths with NSFCAM, the facility near-infrared imager, each time it is used on the telescope. The filters utilized include a 1.58-micron continuum band, a 2.3-micron filter centered on a strong methane absorption, an L' filter, a Circular Variable Filter setting of 3.55 microns used for monitoring H3+ emission, and a 4.78-micron filter sensitive to thermal radiation escaping through low-opacity regions of Jupiter's atmosphere. The entire data set, which is comprised of more than 72,000 files, has been deposited at the Planetary Data System (PDS) Atmospheres Discipline Node and is currently undergoing final validation and peer review.
A subset of the 1.58 micron continuum images of Jupiter has been analyzed with the objective of characterizing the temporal variation of the physical properties of the ammonia cloud deck. An understanding of the long-term behavior of Jupiter's uppermost cloud will aid in the interpretation of the Galileo data set. The IRTF images with the highest spatial resolution were selected for reduction, and these data were geometrically navigated to determine Jupiter's north orientation. The Jupiter images were photometrically calibrated using standard star data, and measurements of Jupiter's center-to-limb reflectivity were obtained across several different latitudes. These scans were modeled using an adding-doubling radiative transfer code, which iteratively fits for the ammonia cloud deck single scattering albedo. Preliminary results of this modeling effort will be discussed.
Support for this work comes from the PDS (JPL Contract Number 1224513) and NASA's Planetary Astronomy Program.