Characterization of STARDUST target comet 81P/Wild 2 from 1996 to 1998^*

¹ Research and Scientific Support Department of ESA, ESTEC, Postbus 299, 2200AC Noordwijk, The Netherlands e-mail: Rita.Schulz@esa.int
² Sterrewacht Leiden, Postbus 9513, 2300RA Leiden, The Netherlands e-mail: stuwe@strw.leidenuniv.nl
³ European Southern Observatory Chile, Alonso de Cordova 3107, Santiago, Vitacura, Chile e-mail: hboehnh@eso.org
⁴ Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720, USA e-mail: Wolfgang.Gaessler@SubaruTelescope.org
⁵ Osservatorio Astrophisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: tozzi@arcetri.astro.it

Corresponding author: R. Schulz, Rita.Schulz@esa.int

Received: 11 March 2002
Accepted: 5 November 2002

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 long-lasting fan structures, which remained essentially unchanged for at least three months. The () and () 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.