Scientists at the
"We made it!" Rosetta Spacecraft Operations Manager
Its target is the Churyumov-Gerasimenko comet, which it's due to reach in August.
After receiving the alarm call, the craft began a six-hour wake-up procedure that included switching on some heaters to warm the units that control direction, ESA's head of mission operations,
Then the instruments had to halt the rotation of the craft, point an antenna to Earth and transmit a signal.
In May, they'll begin to slow the craft down to a pace of a few meters per second from 1km per second, he said.
"Then we will be starting the final approach, and in August we can basically say we are in orbit around the comet," Ferri said. "That's when we start our phase of detailed characterisation of the comet and we take pictures and we measure the gravity potential."
Astrium, now part of Airbus Defence and Space, was the main contractor for the spacecraft launched on
After reaching the Churyumov-Gerasimenko comet,
"The mission is staying around the comet, studying it and seeing its evolution as it gets closer to the sun," said Ferri.
When the lander is in place, it will shoot two harpoons into the comet to anchor it. The main craft will be "flying over the landing site, collecting signals, storing them on board and periodically pointing the antenna to Earth to send them back," he said.
While Philae would be the first probe to touch down on a comet and beam data back, ESA's first deep-space mission, Giotto, was sent to investigate Halley's Comet in 1986.
In early 2006, the agency's Stardust spacecraft returned samples to Earth that were collected during a seven-year round trip to the comet Wild 2. The mission had used a tray of silica gel to trap particles flying off the comet.
ESA's Giotto in 1986 passed near the nucleus of Halley's comet, capturing images of the nucleus and discovering the first evidence of organic material in a comet. In 1992, the same craft passed near a second comet, Grigg-Skjellerup.
Since then, only the computer and some heaters have been active. Because of
"For mission control, not having the signal of the spacecraft is the worst thing that you can have," Ferri said.
"When we have a signal, we know what is the status. Even if there are problems with the spacecraft we can intervene. Even though it was planned, two-and-a-half years without contact is very bad."
The Churyumov-Gerasimenko comet orbits the sun every 6.6 years at a distance that ranges from 186 million kilometres to 857 million kilometres.
Discovered in 1969, the comet has a nucleus estimated to be 4km in diameter.
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