Dust impacts at Comet P/Borrelly

Abstract

The NASA DS1 spacecraft flew past comet P/Borrelly on September 22, 2001, on the sunward side of the comet. Dust impacts were detected by sharp increases (or decreases) in electric fields measured by the plasma wave dipole antennae. Electric pulses from as small as 0.014 Vm−1 to saturation (∼±0.8 Vm−1) were detected. Pulse overshoots were noted in the largest electric pulses. No simultaneous dc magnetic signatures >1 nT were detected in the magnetometer data. Assuming that cometary dust grains propagating in the sunward direction were decelerated by solar radiation pressure, arguments are made that the size of the earliest dust particles detected were probably ∼0.4 μm in radius. Elaboration of the characteristics of these electric pulses and pulse overshoots and their interpretations will be reserved for a subsequent work.