Galileo and Ulysses dust measurements: Fz Venus to Jupiter

Abstract

The Galileo and Ulysses spaceprobes carry two similar dust detectors through interplanetary space from Venus to Jupiter. We report here on impacts which correspond to dust particles above a mass threshold of about 10−13g for which we have complete records. Between December 1989 and January 1992 Galileo repeatedly traversed interplanetary space between 0.7 and 2.26 AU and recorded 374 impacts. The observed impact rates ranged from 0.1 to about 3 impacts per day strongly dependent on whether the spacecraft moved towards or away from the Sun. From October 1990 to January 1992 the Ulysses spacecraft had reached a distance of 5.17 AU from the Sun and had recorded 72 impacts at rates between 0.1 and 0.5 per day. Inside about 2 AU the observed fluxes are compatible with a population of interplanetary dust particles moving on low to moderately eccentric (e = 0.1 to 0.5) and low inclination (i = 0 deg. to 30 deg.) orbits. Outside this distance a dust particle population on different orbits is required in order to explain the Ulysses data.