Time to take my weekly census of the spacecraft exploring the solar system. I wrote the Cassini part of this update yesterday but didn't have time to finish, and I've been trying to be a good girl about not working after hours -- so I'm a day later than usual, which is unfortunate because my first item was: Happy birthday to Cassini! On this day [which is to say, yesterday], four years ago, Cassini went into orbit at Saturn. The four-year ....