After seven months in hibernation on a comet, the space probe Philae has woken up

ESA's space probe Philae has awoken on comet 67P/Churyumov–Gerasimenko after seven months in hibernation. 

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On November 12, 2014, Rosetta ejected the dishwasher-sized, tendril-like limbed Philae into the quiet abyss of space. Its mission: to land on a comet with feeble gravity that moves 40 times the speed of a bullet:

Rosetta’s OSIRIS narrow-angle camera shows the Philae lander at 10:23 GMT (onboard spacecraft time) on 12 November, almost two hours after separation. Image: ESA

In a bid to become the new hero of new-age space technology, Philae, despite its harpoons malfunctioning, and despite its bumpy landings, found itself miraculously wedged in a rocky crevice on comet 67P Churyumov-Gerasimenko. Its rather fortunate position sent back (via Rosetta) some intriguing images of the comet’s shadowed surface:

A spot on the comet's surface before it landed is empty (left) and then after the landing a new blip appeared (middle and right). Image: ESA

A cosmic power was on Philae’s side that day. Had the trajectory of the bounce(s) been a few kilometres too high, and/or had Philae’s harpoons tried to pierce into comet 67P's harder-than-expected icy subsurface, Philae might have not made history.

On 15 November, the 500m km distance between Philae and the Sun became a little too long to handle. Soon after the champagne popped upon Philae's landing, its batteries began rapidly depleting because there was not enough sunlight needed to recharge them.

The engineers of European Space Agency (ESA) were, behind the smiles, all too aware of this, and before its termination, commanded Philae to rotate enough to get one of its solar panels into sunlight. It helped. Like a hedgehog with a belly swollen with food, it protected itself from the cold winter months ahead, by going into hibernation.

The hope was as the comet rotates towards the Sun, Philae would get enough solar energy through its panels to wake as the Sun rises. 

On Saturday at 20:28 UTC, at a distance from the Sun of about 200m km, Philae woke up! The signal from the lander (via Rosetta) was received by the European Space Operation Centre. Philae will make its closest encounter to the Sun on 13 August.  

"Philae is doing very well: It has an operating temperature of -35ºC and has 24 Watts available," explained DLR Philae Project Manager Dr Stephan Ulamec. "The lander is ready for operations."

According to ESA, Philae "spoke" with its team on ground for 85 seconds, via Rosetta, in the first contact since going into hibernation in November. When analysing the status data, it became clear to the ESA team that Philae also must have been awake earlier: "We have also received historical data – so far, however, the lander had not been able to contact us earlier," Ulamec added.

Due to the ESA astronomers' unwavering resilience, the Rosetta mission is the first ever to orbit a comet. Philae is the first lander to touch down on a cometary surface, and the first to wake from slumber on a speeding comet.

The scenes on comet 67P last November filled viewers with joy and fear – from Philae landing on the comet, to Philae bouncing off the comet due to the malfunctioned harpoons and consequently losing signal with Rosetta mission control. 

When Professor Mark McCaughrean, ESA’s Senior Science Adviser, heard Philae had woken up, it was half past ten at night and he and his colleagues couldn't sleep because of the excitement, he tells me. When the word finally got out to the media, the public went “nuts”, he adds.

The scientists are now waiting for the next contact with Philae. More than 8,000 data packets remain in Philae’s mass memory that will give the DLR team information on what happened to the lander in the past few days on the comet.

For now, Philae’s health will be examined. New data is expected to be sent which will hopefully include the exact location of Philae. That’ll give engineers the best methods to deal with the lander’s orientation, as well as to continue the Rosetta mission – a mission in which its prime objective is to understand the origin and evolution of the Solar System.

For more updates and current info, follow the ESA's Rosetta blog.

Tosin Thompson writes about science and was the New Statesman's 2015 Wellcome Trust Scholar.