Infrared observations of Comet 81P/Wild 2 in 1997

Comet 81P/Wild 2 was observed in the thermal infrared over 6 months during its 1997 perihelion passage. The comet was most active in late February, about 3 months preperihelion; dust production declined by a factor of 3 between February and August. For the GIOTTO Halley dust size distribution, maximum dust production rate was similar to2 X 106 g/s. The comet displayed a 10-mum silicate feature about 25% above the continuum, similar to several other Jupiter-family comets, but much lower than that seen in a number of Oort cloud comets. NASA's STARDUST sample return mission will encounter P/Wild 2 98 days postperihelion in January 2004. Based on our observations at a similar point in the orbit and the Halley size distribution, we predict that the mass fluence on the spacecraft for a 150 km miss distance will be about 8 x 10(-6) g/cm(2) for particles up to 1 cm in radius. The corresponding areal coverage will be about 10(-4). (C) 2003 Elsevier Science (USA). All rights reserved.