shown in the right panel. The camera pointed 30
off the nightside limb with the
spacecraft 142 km from the nucleus. The spacecraft moves during the exposure
producing smear. The vertical dot-dashed line here shows the angle one would
expect if a particle were stationary and the track were solely from this motion of
the spacecraft. (This angle actually shows slight dependence upon the distance of the
spacecraft to the particle. Stars would also appear close to this angle.) One can plot
the brightness of the streaks against their length (bottom left) and this shows a strong
concentration at low speed and a particular I/F. But of course, the faster a particle is,
Fig. 4.53 A jet emitted from the nucleus showing very little slow large particle emission. The jet
structure is fairly smooth. Interestingly, at the position of the arrow, some dark tracks can be seen.
One possible explanation is that these are large particles between the camera and the smooth jet. The
particles are either weaker scatters than the jet material or are in shadow. (Image number:
N20151207T062446727ID10F22)
362
4 Dust Emission from the Surface