Comet-chasing probe wakes up, signals Earth
Waking up after more than two years in hibernation, a comet-chasing spacecraft sent its first signal back to Earth on Monday, prompting cheers from scientists who hope to use it to land the first space lander onto a comet.
BERLIN — The comet-chasing Rosetta spacecraft sent its first signal back to Earth after a 31-month hibernation on its decadelong mission into deep space.
Scientists at the European Space Agency’s mission control in Darmstadt, Germany, jumped up and cheered when the signal registered Monday morning.
Made from dirty ice, dust and gas, they are considered building blocks that likely helped seed Earth with water and possibly even life. Rosetta’s target is the Churyumov-Gerasimenko comet, which it’s due to reach in August.
After receiving a wake-up call, the craft began a six-hour wake-up procedure that included switching on some heaters to warm the units that control the direction it points, said ESA’s head of mission operations, Paolo Ferri. Then the instruments had to halt the rotation of the craft, point an antenna to Earth and transmit a signal.
NASA’s monitoring station in Goldstone, Calif., was used to pick up the signal.
Rosetta’s scientists will now test all of its subsystems and activate each of the craft’s scientific instruments in turn between now and April, according to Ferri. In May, they’ll begin to slow the craft down from 1 kilometer per second to a pace of a few meters 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 characterization of the comet and we take pictures and we measure the gravity potential.”
Astrium, now part of Airbus Defense and Space, was the main contractor for the spacecraft launched on March 2, 2004.
After reaching the Churyumov-Gerasimenko comet, Rosetta is scheduled to orbit until the end of 2015 and to place its lander, called Philae, on the icy mass this November after identifying a suitable site.
Rosetta has 11 packages of scientific instruments and Philae 10.
“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,” Ferri 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. The U.S. National Aeronautics and Space Administration has also launched two missions to study comets in the past 20 years.
Rosetta is currently about 416 million miles from the sun and more than 500 million miles from earth, according to ESA. Its planned hibernation began in June 2011 because it was too far from the sun for its solar panels to generate sufficient energy. Since then, only the computer and some heaters have been active to ensure the craft didn’t freeze.
“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, 2½ years without contact is very bad.”