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D.K. Yeomans, S.R. Chesley, N. Mastrodemos (JPL/Caltech)
On July 4, 2005 the impactor portion of the dual Deep Impact spacecraft will collide with short period comet 9P/Tempel 1 while the flyby spacecraft will observe the comet crater formation process. The primary mission science goals are to infer the structure of the comet's nucleus, compare the nucleus surface to the interior, and better understand its interior composition. To successfully carry out the impact on a sunlit portion of the nucleus and on the same side as the flyby spacecraft's trajectory requires 1.) an accurate pre-encounter cometary ephemeris development, 2.) spacecraft navigation to the neighborhood of the comet, 3.) optical navigation images of the comet and subsequent updates to the comet’s ephemeris, and 4.) independent autonomous navigation of the impactor and flyby spacecraft prior to, and during, the encounter. The problems peculiar to each of these navigation phases will be outlined, the error sources noted and a description provided for the efforts carried out to ensure the 3-sigma impact targeting uncertainty is no larger than 700 m - about 5% of the comet's longest axis.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.