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K. Clancy, J. L. Elliot, M. J. Person, K. M. Carbonari, A. J. Klesman, E. L. McEvoy, J. Meechai, S. Qu (MIT), E. W. Dunham (Lowell), A.S. Bosh (Boston Univ.& Lowell), M. W. Buie, L. H. Wasserman, A. Morrison (Lowell), R. C. Stone, S. E. Levine (USNO)
Methods of accurately predicting Pluto's shadow's path across Earth during an occultation--well in advance of the event--have long been sought after as means of aiding logistic preparation for observations. Positions of Pluto and the occulted star P126A were derived from a number of telescopes: the Lowell Astrograph, FASTT, USNO 61-inch reflector, and the Lowell 0.6-m telescope at CTIO. Strip scan CCD data were taken at the Lowell Astrograph, which avoided systematic errors associated with local inaccuracies in the astrometric catalog. However, the strip scans introduced systematic errors of their own, which were addressed. As P126 proved to be a binary star, the separation of its components and the light ratio between the two were determined from resolved USNO data and used in fitting the unresolved strip-scan images. The B component of P126 was found to be much redder than the occulted component, so the light ratio P126B/P126A for different filters used for the astrometric observations had to be calibrated. In these astrometric data, the residuals of Pluto from its ephemeris showed a periodic variation at the Pluto-Charon period, which suggests either an error in the Charon/Pluto light ratio used, the mass ratio used, or both. Modeling these residuals allowed us to correct the measurements derived from the data taken a few days before the event. The final prediction (http://occult.mit.edu/research/occultations/Candidates/Predictions/P126.html) was less than 100 km from the actual path of Pluto's shadow across the Earth (see Buie et al., this conference). This work was supported, in part, by NASA Grants NAG5-9008 and NAG5-10444.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.