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R. Schulz (ESA/SSD), J. Stüwe (Univ. Bochum, Germany)
We report the results of our analysis of broad-band filter images of Comet 81P/Wild 2, the target comet of the STARDUST mission. The images were obtained with the 2.2m telescope at the European Southern Observatory, La Silla, Chile, in September and December 1996. As such they give a glimpse into the preperihelion evolution of comet 81P/Wild 2 between r = 2.6 AU (\Delta= 2.8 AU) and r = 2.1 AU (\Delta = 1.3 AU). In September only R band images were obtained, while in December the comet was imaged in R and V. All images were flux calibrated and the R (and V) brightnesses were investigated as a function of distance from the nucleus, \rho, for both observing runs. For December the V-R color of the coma could be derived. The coma was slightly redder than the sun, V-R = 0.46 (solar: 0.37), which is expected if the broad-band filter images reflect mainly the cometary dust. Hence, it can be concluded that the V exposure obtained at r = 2.1 AU was not yet significantly contaminated by gaseous (mainly C2) emission. The morphological analysis of the images revealed that comet 81P/Wild 2 exhibited a jet-like structure almost perpendicular to the sun-tail direction. The structure is detectable in all images obtained in September and December 1996. It does not show up in the V-R images, which means that the color of the dust composing the structure is not different from that of the underlying coma.