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T. M. Ho, N. Thomas, C. Kollein (Max-Planck-Institut fuer Aeronomie), D. C. Boice (SWRI, San Antonio), T. Bonev (Institute of Astonomy, Sofia), K. Jockers (Max-Planck-Institut fuer Aeronomie), K. J. Meech (University of Hawaii), L. A. Soderblom (USGS, Flagstaff), R. Yelle (North Arizona University)
On September 22nd 2001 Deep Space 1 passed by comet Borrelly. We present our analysis of the data received by the MICAS experiment onboard the spacecraft. One can recognize strong collimated dust jets on all the images of the comet. In particular a major dust jet on the sunward side of the nucleus was observed. To analyse these features we integrated the observed intensity in concentric envelopes around the nucleus. The same procedure is used on the HMC (Halley Multicolour Camera) images of comet Halley acquired on March 14th 1986. We could see that the dust brightness dependence as a function of radial distance of Borrelly is remarkably different to that of Halley. While the main causes for Halley's intensity evolution could be high optical thickness or particle fragmentation effects, in Borrelly's case it is likely caused by the fact that the dust is not emitted from a point source. We have tried to constrain the possible causes by simulating dust emission cones on a nucleus surface and by comparing the obtained results with the real data. We also have used ground based observations of comet Borrelly to determine the outflow velocity of the dust.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.