Robot probe Philae has uploaded a slew of last-minute data to Earth from a comet in deep space, before going to sleep at the conclusion of a historic exploration, ground controllers said.
Data streamed in as soon as Europe's pioneering robot lab reestablished late-night contact with its orbiting mothership, Rosetta, but its limited battery soon started wavering.
"My #lifeonacomet has just begun," said an official tweet in the name of the washing machine-sized lander perched on comet 67P/Churyumov-Gerasimenko since Wednesday -- concluding with a restful "zzzzz".
"S'ok Philae, I've got it from here for now. Rest well...," said a response tweeted on behalf of Rosetta. The European Space Agency (ESA) said its robot lab had entered "idle mode", with all instruments and most systems shut down after three days of non-stop work -- taking pictures and probing the comet's density, temperature, composition and atmosphere.
"Prior to falling silent, the lander was able to transmit all science data gathered," said a statement. The lander and its mothership, which relayed Philae's data to Earth, had only two communications windows per day -- the last opened around 0300 IST on Friday and closed at 0606 IST the next morning as Rosetta disappeared in orbit behind the comet.
Mission controllers had feared the robot may not even have enough power to make contact during this window -- but they were pleasantly surprised. "Science from an alien world" ESA Operations tweeted when contact was made. "Info now flowing from @ Philae2014."
The channel should open again around 0630 IST today, but lander manager Stephan Ulamec told AFP from mission control in Darmstadt, Germany, he did "not really expect" contact with Philae then.
"The chances that we could reestablish the link again tomorrow are really very, very low," he said. "The battery is not completely empty, but it is below the level the central computer needs to boot" up. In one of many jaw-dropping achievements, the robot lab appears to have lifted itself slightly on Friday and rotate the larger of its solar panels to absorb as much energy as possible to be stored for a possible wakeup later.
Philae had landed in a dark ditch after a bouncy touchdown Wednesday, and did not get enough sunlight to recharge its batteries sufficiently to extend its mission.
Mission engineers dream, however, of making contact with the lander "at some point" in the coming months as the comet, with Philae hopefully still clinging to its surface, moves closer to the Sun.
Philae's historic on-site survey of a comet travelling at 18 kilometres per second, currently at a distance of 510 million kilometres from Earth, is the highlight in a more than decade-long mission.
Philae landed Wednesday after a nail-biting seven-hour, 20-km descent from Rosetta, which had travelled more than a decade and 6.5 billion kilometres to meet up with the comet in August this year.