Cassini’s Grand Finale findings puzzles several scientists. The narrow gap region between Saturn and its rings, appears to be dust-free.
The relatively dust-free gap has broken down the basic assumption. The assumption of a dustier environment in the gap lead to the spacecraft’s saucer-shaped main antenna. Cassini team created it to act as a shield during most future dives through the ring plane. So far no space craft had ever passed through this region. The shield was created as a precautionary step to avoid the affects of dust on the spacecraft.
Cassini’s Radio and Plasma Wave Science (RPWS) instrument is one of two science instruments with sensors that poke out from the protective shield of the antenna. RPWS detected the hits of hundreds of ring particles per second when it crossed the ring plane just outside of Saturn’s main rings. But it detected only a few pings on April 26, while passing through the narrow gap. When RPWS data are converted to an audio format, dust particles hitting the instrument’s antennas sound like pops and cracks. They cover up the usual whistles and squeaks of waves in the charged particle environment. The RPWS team expected to hear a lot of pops and cracks on crossing the ring plane inside the gap, but instead, the whistles and squeaks came through surprisingly clearly on April 26.
Based on images from Cassini, models of the ring particle environment in the approximately 2,000-kilometer-wide region between Saturn and its rings suggests that the area would not have large particles that would pose a danger to the spacecraft. The team’s analysis suggests Cassini only encountered a few particles as it crossed the gap. Added to this, no particle was larger than those in smoke (about 1 micron across).
With this information in hand, the Cassini team will now move forward with its preferred plan of science observations.
