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T. L. Farnham, M. F. A'Hearn (U. Maryland), M. J. S. Belton (BSEI), C. J. Crockett (U. Maryland), A. Delamere (Ball Aerospace, Ret.), O. Groussin, J.-Y. Li (U. Maryland), C. M. Lisse (JHU APL), L. A. McFadden (U. Maryland), K. J. Meech (U. Hawaii), D. D. Wellnitz (U. Maryland), Deep Impact Team
On July 4, 2005, the Deep Impact spacecraft encountered Comet 9P/Tempel 1. During the approach and encounter phases, DI obtained medium and high resolution images of the coma and nucleus. In the coma, narrowband filters were used to isolate the emissions from different gas species as well as sampling the reflected light from the dust at several different wavelengths. Images were obtained at frequent intervals, with both short and long exposures. The short exposures capture the surface details on the nucleus, while the long exposures show the morphology of the coma. Combining these images allows an investigation of the relationship between the two.
During the approach phase, jets were observed in the coma, turning on and off and producing arcs (archimedean spirals) that expanded outward from the rotating nucleus. These images provide temporal information about the jets and their reactions to diurnal changes in the solar irradiation, and can be used, with the known rotation state and shape of the nucleus, to derive locations of the active regions on the surface. Additional data, obtained during the close approach, show linear jets (likely the inner segments of the archimedean spirals). Because of the 41-hour rotation period and the rapid flyby, changes in these jets is predominantly due to perspective differences in the spacecraft's viewpoint. Thus, pairs of images contain stereo information that can be used to trace the jets back to their origins on the nucleus. Finally, data from different filters can be used to compare the relative compositions of different jets, or the colors of the dust, to search for variations that may reveal inhomogeneities in different portions of the nucleus. We will present results from an analysis of these data.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.