3. Cassini Arrives I t's July 1, 2004, and Cassini's long trek to its destination is over. In just one hour and fifty-two minutes, the spacecraft will be closer to Saturn than at any other time during its mission. The engine burn that will curtail Cassini's interplanetary trajectory and deflect it into orbit around Saturn--Saturn Orbit Insertion, or SOI--is only minutes away. This burn will be the most critical event of the mission since launch. But first the spacecraft is crossing through the ring plane. To minimize the risk from a collision with a ring particle, it makes its passage through the rings in the large gap between the F and G rings. Shortly after Cassini has crossed above the rings, the main engine burn begins at 01:12 Coordi- nated Universal Time (UTC) and continues for ninety-six minutes. ............................................................................................................ RALPH'S LOG, JULY 1, 2004 I spent part of the morning filming with the BBC, driving up and down Pasadena's Colorado Boulevard pretending to "commute," and then pretending to check my e-mail on a laptop in a motel room (not my own). Just like the hundreds of contingency plans, backup sequences, or observation de- signs that don't get used on a space mission, the media take a lot more footage than they actually use, and thankfully this pedestrian stuff fell onto the cutting room floor. Saturn Orbit Insertion would be somewhat tense. A couple of Mars missions had been lost at just such arrivals, when fuel 67