NASA’s Cassini to fly between Saturn, rings

CAPE CANAVERAL, Fla. — NASA’s Cassini spacecraft faces one last perilous adventure around Saturn.

Cassini swings past Saturn’s mega moon Titan early Saturday for a gravity-assisted, orbit-tweaking nudge.

“That last kiss goodbye,” as project manager Earl Maize calls it, will push Cassini onto a path no spacecraft has gone before — into the gap between Saturn and its rings. It’s treacherous territory. A particle from the rings — even as small as a speck of sand — could cripple Cassini, given its velocity.

Cassini will make its first pass through the relatively narrow gap Wednesday. Twenty-two crossings are planned, about one a week, until September, when Cassini goes in and never comes out, vaporizing in Saturn’s atmosphere.

Launched in 1997, Cassini reached Saturn in 2004 and has been exploring it from orbit ever since.

“What a spectacular end to a spectacular mission,” said Jim Green, NASA’s planetary science division director. “I feel a little sad in many ways that Cassini’s discoveries will end. But I’m also quite optimistic that we’re going to discover some new and really exciting science as we probe the region we’ve never probed before.”

The spacecraft will hurtle through the 1,200-milewide gap between Saturn’s atmosphere and its rings, at a breakneck 70,000-plus mph.

From a navigation standpoint, “this is an easy shot,” Maize said. The operation will be run from NASA’s Jet Propulsion Laboratory in Pasadena, Calif. The concern is whether computer models of Saturn’s rings are accurate. On a few of the crossings, Cassini is “kind of flirting with the edge of where we think it’s safe,” he noted.

This last leg of Cassini’s 20-year, $3.27 billion voyage should allow scientists to measure the mass of the multiple rings — shedding light on how old they are and how they formed — and also to determine the composition of the countless ring particles.

First spotted by Galileo in 1610, the rings are believed to be 99 percent ice; the remaining 1 percent is a mystery, said project scientist Linda Spilker. A cosmic dust analyzer on Cassini will scoop up ring particles and analyze them.