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Session 9 - Instruments, Techniques.
Display session, Monday, June 09
South Main Hall,

[9.01] Photometric Imaging of the Moon from Flagstaff: A Progress Report

J. M. Anderson (NAU/USGS)

The U.S. Geological Survey and the Northern Arizona University operate a highly automated observatory atop McMillan Mesa on the grounds of the U.S. Geological Survey's Flagstaff Field Center. The primary purpose of the observatory is to provide accurate radiance information of the Moon for calibration of Earth-orbiting instruments, particularly Earth Observing System instruments. Current instrumentation includes a 20 cm diameter Ritchey-Crétien telescope on a computer controlled mount designed for a 41 cm telescope. The imaging device is a 512x512 CCD with a resolution of 4.0 arcsec/pixel. Interference filters within 350--950 nm are used to correspond to standard stellar bandpasses, wavelengths of high lunar contrast, and approximate bandpasses of planned Earth-orbiting instruments. A full aperture radiance calibration source ties observations to an absolute radiance system. A second instrument operating from 0.95--2.4 \mu m is under construction and will be added to the same mount as the present instrument.

Since March 1996 observations have been made every clear night during the bright half of each month. Both stars and the Moon are observed by the same equipment; photometric standard stars are observed each night to provide long-term stability in the radiance calibration of lunar images and to determine atmospheric extinction. Real-time software determines object targeting, calculates optimal exposure times, commands telescope pointing, and controls data acquisition. Semi-automated routines backup data to remote disks and archive data onto CD-ROMs. Over 100\,000 images were generated by this system during 1996, necessitating the development of automated software to reduce lunar images to exoatmospheric radiance projected in a fixed selenographic grid system. These radiance images will be further reduced to photometric models for individual grid points, from which radiance models can be produced for the precise geometry of spacecraft observations.

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