Characterization of STARDUST target comet 81P/wild 2 from 1996 to 1998

Abstract

We present the results of our monitoring of comet 81P/Wild 2, the target of the STARDUST mission. Broad-band filter images and medium resolution spectra of this comet obtained along its pre- and postperihelion orbit between 1996 and 1998 were analysed in terms of coma morphology and activity. The morphological coma investigation revealed the presence of longlasting fan structures, which remained essentially unchanged for at least three months. The (B - V) and (V - R) colour indices were determined at three different positions along the orbit. The two-dimensional analysis showed a uniform colour over the entire coma. Hence, the material composing the structures is not different from that of the underlying coma. The distribution of coma brightness as a function of projected distance from the nucleus shows no peculiarities. The evolution of the comet's activity during the pre- and postperihelion phase appears to be asymmetric in that activity increases faster preperihelion than it decreases postperihelion. The production rates (or their upper limits in the case on a non-detection) of CN, C2, C3, and NH2 were determined from the spectrophotometric observations and compared to other values published in the literature.