Waking up after almost three years of 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.
The European Space Agency received the all-clear message from its Rosetta spacecraft at 1:18 p.m. EST — a message that had to travel some 500 million miles.
In keeping with the agency’s effort to turn the tense wait for a signal into a social-media event, the probe triggered a series of “Hello World!” tweets in several languages.
Dormant systems on the unmanned spacecraft were switched back on in preparation for the final stage of its decade-long mission to rendezvous with the comet named 67P/Churyumov-Gerasimenko. Systems had been powered down in 2011 to conserve energy, leaving scientists in the dark about the probe’s fate until now.
The wake-up call is one of the final milestones for Rosetta before it makes its rendezvous with comet 67P in the summer. The probe will then fly a series of complicated maneuvers to observe the comet — a lump of rock and ice about 2.5 miles in diameter — before dropping a lander called Philae onto its icy surface in November.
The lander will dig up samples and analyze them with its instruments.
Although the spacecraft was launched almost a decade ago, the instruments aboard Rosetta and the Philae lander are still considered cutting edge, said Joel Parker of the Southwest Research Institute in Boulder, Colorado. The institute developed a specialized camera called ALICE that can detect various chemicals in the comet.