Mass-loss rates, dust particle sizes, nuclear active areas and minimum nuclear radii of target comets for missions STARDUST and CONTOUR

Observed visual magnitudes of the short-period comets 2P/Encke, 81P/Wild 2, 6P/d'Arrest and 73P/Schwassmann-Wachmann 3 and the long-period comet C/198 4 V1 Levy-Rudenko are converted into water release rates. These H2O release rates are used to derive the nuclear surface areas, minimum nuclear radii and gas mass loss of these comets. Combined with estimated gas release rate s, we make an uniform and systematic analysis of the observed continuum flu xes in the comae of these comets with the objective to find dust release ra tes, effective dust particle sizes and total mass release rates. The nuclei of Comets 2P/Encke, 6P/d'Arrest and 73P/Schwassmann-Wachmann 3, which has split into as many as four fragments, are potential targets for the flyby o f the CONTOUR (COmet Nucleus TOUR) spacecraft, scheduled for launch in 2002 July, while Comet 81P/Wild 2 has been chosen as a target by the NASA space craft STARDUST, which was launched on 1999 February 7.