The Philae lander space probe thought lost has woken up some seven months after officials thought it marooned in the shadows on a comet, the European Space Agency said.
The probe became the first spacecraft to land on a comet when it left the orbiting Rosetta mothership and touched down on the surface of 67P/Churyumov-Gerasimenko in November.
Mission controllers put the lander to sleep after power in its batteries dwindled to dangerous levels, but not before the craft transmitted a flood of science data to Earth.
Hello @ESA_Rosetta! I'm awake! How long have I been asleep? #Lifeonacomet
— Philae Lander (@Philae2014) June 14, 2015Upon contacting the comet’s unexpectedly hard surface, it bounced back up into space twice then came to rest at a still-unknown location about 1km from its original target.
Photos and other data relayed by Philae show it finally landed against a cliff or crater wall where there was little sunlight to recharge its batteries. Racing against the clock, scientists activated a series of automated experiments, the first to be conducted from the surface of a comet.
Before dying 60 hours after landing, Philae defied the odds and radioed its science results back to Earth for analysis.
Its last task was to reposition itself so that as the comet soared towards the sun, Philae‘s batteries could recharge enough for a follow-on mission.
Philae’s landing on a fast-moving comet 500 million kilometres away has been hailed as one of humankind’s greatest scientific achievements.
Scientists believe that the probe is receiving increasing amounts of sunlight as the comet speeds closer to the sun, enabling its solar panels to produce the power needed for it to send data. In the shadows, Philae’s solar panels, which were meant to power the probe after its batteries ran out several days after landing, received far less than the expected six to seven hours sunshine per day.
The ESA said the probe communicated with the ground team on Earth for 85 seconds yesterday.
Philae resumed communication at 10.28pm local time last night, sending about 300 packages of data to Earth via the Rosetta.
"Philae is doing very well," said project manager Stephan Ulamec in a statement on ESA's website. "The lander is ready for operations."
Mr Ulamec said the probe appears to have been awake for some time before it called home, because some of the packages received contain historical data.
Scientists hope that samples drilled from the comet by Philae will unlock details about how the planets - and possibly even life - evolved. The rock and ice that make up comets preserve ancient organic molecules like a time capsule.
Philae has more than 8,000 data packages still stored in its memory, which scientists hope to receive when the probe next communicates with Earth. The data contained therein may help them determine where Philae has landed.
The probe’s exact location has been a mystery, though scientists have narrowed down its likely location based on images and other measurements received from Philae and Rosetta.