The Ulysses spacecraft is orbiting the Sun on a highly inclined ellipse ( i = 79 ^ { \circ } ) .
After its Jupiter flyby in 1992 at a heliocentric distance of 5.4 AU , the spacecraft reapproached the inner solar system , flew over the Sun ’ s south polar region in September 1994 , crossed the ecliptic plane at a distance of 1.3 AU in March 1995 , and flew over the Sun ’ s north polar region in July 1995 .
We report on dust impact data obtained with the dust detector onboard Ulysses between January 1993 and December 1995 .
We publish and analyse the complete data set of 509 recorded impacts of dust particles with masses between 10 ^ { -16 } g to 10 ^ { -7 } g. Together with 968 dust impacts from launch until the end of 1992 published earlier ( Grün et al. , 1995 , Planet .
Space Sci , Vol .
43 , p. 971-999 ) , information about 1477 particles detected with the Ulysses sensor between October 1990 and December 1995 is now available .
The impact rate measured between 1993 and 1995 stayed relatively constant at about 0.4 impacts per day and varied by less than a factor of ten .
Most of the impacts recorded outside about 3.5 AU are compatible with particles of interstellar origin .
Two populations of interplanetary particles have been recognised : big micrometer-sized particles close to the ecliptic plane and small sub-micrometer-sized particles at high ecliptic latitudes .
The observed impact rate is compared with a model for the flux of interstellar dust particles which gives relatively good agreement with the observed impact rate .
No change in the instrument ’ s noise characteristics or degradation of the channeltron could be revealed during the three-year period .