[X] My Assistant

[angel1801]

Apart from Titan, will Cassini get close to any icy moons when it gets into the inner part of Saturn on or around April 30? I've checked using the Solar System Simulator and I have not seen anything good to date.

[edstrick]

The article on Voyager 2's Saturn encounter that had that information almost certainly said what caused the 1 degree (I think that's about what it was) roll error, but I do not recall what it was. I suspect it may have been gyro drift during the fields and particles roll maneuver, or as likely or more so a simple command or spacecraft-behavior prediction error.

Voyager's attitude control was distinctly sloppy compared with the narrow angle field of view, though nowhere near as wobbly as Mariner 10's. Mission planning shows neat grids of narrow angle mosaics across Mercury, but the actual image sequences show curves and and wanderings more than one field of view in a few cases.

Voyager's attitude control became considerably tighter due to very very hard work testing the limits of the hardware and tweeking the attitude control software after Saturn flyby in preparation for the low light level work at Uranus and even lower light levels at Neptune. The performance improvement they got was astonishing. Some image sequences at Saturn were image motion blurred, while much of the Triton imaging at Neptune was essentially rock steady.

[ugordan]

Janus UV3-GRN-IR1 composite, distance ~220 000 km:

The image on the right is enhanced to bring out color differences across the disk.

[ugordan]

Rhea from ~481 000 km, R+B composite with a synthetic green:

The image on the right was taken two months ago, also showing "the splat", but using UV3-GRN-IR1 filters. The distance at that time was around 350 000 km. Note the right-hand image has Rhea's north directly up, while the left-hand one was taken with the sunlight coming directly from left and is thus slightly rotated clockwise.