4.9 billion miles later, orbiter set to end mission
It was conceived when Ronald Reagan was in the White House. It launched in 2004 a few weeks after Mark Zuckerberg created Facebook in his Harvard dorm. It spent a full decade looping around the solar system. And when it finally caught up with its target, it deployed the first probe to land on a speeding comet and survive.
Now the long, dramatic journey of the Rosetta space orbiter is about to end. After logging 4.9 billion miles, the craft is set to commit operational suicide in the wee hours of Friday morning, deliberately falling to the surface of 67P/ChuryumovGerasimenko, the mountainsize comet it has been following for two years.
But first it has just a bit more science to do.
During its final descent, Rosetta will gather close-range information about the comet and hastily beam data back to Earth before its main transmitter shuts off for good.
“It’s kind of bittersweet,” said Paul Weissman, a comet scientist at the Planetary Science Institute in Tucson, who worked on Rosetta for 20 years. “You’d like to keep going, but it is also very satisfying. It’s been a tremendously successful mission.”
The $1 billion mission has been full of suspense.
Its many plot twists began before the spacecraft left Earth, when a faulty rocket postponed the launch by two years and caused mission planners at the European Space Agency to abandon their original comet and select a different one instead.
The new comet, known as 67P, was four times larger than the initial target, and meeting up with it required a longer flight than originally planned. Between March 2004 and January of 2014, Rosetta made three Earth flybys and one close pass by Mars, using the planets’ gravity to give it a boost.
Along the way, it imaged two asteroids and endured a hibernation of two years, seven months and 12 days.
Engineers programmed four alarm clocks to wake the spacecraft from its epic slumber. Everything hinged on its ability to boot back up, said Rosetta Flight Director Andrea Accomazzo.
“Either we had a mission, or we had no mission at all,” he said.
Accomazzo got the wake-up signal Jan. 20, 2014 — 40 nailbiting minutes late.
Although the last few minutes of its life are difficult to predict, researchers expect it to hit 67P at a walking pace of slightly less than 3 feet per second. When it lands, it will tumble and bounce before settling into its final resting place. The impact will kick up a few clouds of dark, powdery dust. Then a preprogrammed computer command will turn off its transmitters forever.