Space Probe Cassini Is on Its Final Mission
NASA’s 20-year-old Cassini mission is about to make a final orbit correction that will cause it to crash into Saturn and burn up in September.
Before it meets its fiery demise, however, the long-lived spacecraft, which left Earth in 1997 and first entered Saturn orbit in 2004, will make a series of 22 close flybys, diving within 2,000 km of the giant planet’s cloud tops. Its final passes, in fact, would be so close that it would be able to sample the outer fringes of the planet’s atmosphere, Cassini project manager Earl Maize said at a press conference on April 4 in Pasadena, California.
This Grand Finale, as NASA is dubbing it, begins on April 22 when the spacecraft makes a flyby of Titan, using that moon’s gravity to turn toward Saturn. There it will dive through the gap between the innermost of Saturn’s rings and the giant planet’s atmosphere.
At each of these close approaches, the spacecraft will be traveling 122,000 km/h – fast enough that hitting anything more substantial than a speck of dust could damage it irreparably. “We would never take a flagship mission on that kind of course at any other time in the mission except when it’s about to end,” Maize said.
Cassini’s mission is about to end one way or another, because the spacecraft is on the verge of running out of maneouvring fuel. Project leaders decided years ago that they did not want to leave the spacecraft drifting without maneouvring power, for fear it might eventually crash into one of Saturn’s moons, potentially contaminating it with microbes that had hitchhiked all the way from Earth.
The Grand Finale does more than simply dump the spacecraft safely into Saturn’s atmosphere, where conditions are unsuitable for Earth life. It would also produce some exciting science, said Linda Spilker, the mission’s project scientist: “I would not be surprised if some of the discoveries will be the best we’ve obtained.”