Spacecraft’s receivers activated early on Friday in the hope that probe will make contact during increased exposure to sunlight over coming months.
The European Rosetta spacecraft began to listen out for its robotic lander this morning amid hopes that the comet-riding probe may soon have enough solar power to wake from hibernation.
The Philae lander has not been heard from since its batteries ran out three days after its dramatic and bouncy landing on comet 67P/Churyumov-Gerasimenko in November.
The lander touched down on the comet exactly where mission controllers had planned, but when anchoring harpoons failed to fire, Philae bounced off the surface twice and finally came to a rest against a cliff face that cast a shadow over its solar panels.
Unable to recharge its batteries, Philae went into hibernation. But as the comet speeds towards the sun, mission controllers hope that the probe might receive enough sunlight to awaken and call its orbiting mothership.
In the early hours of Friday morning, scientists at the European Space Agency switched on Rosetta’s receivers in case the probe stirs to life in the coming days. Until May 17, the lander will be in sunlight twice a day when the Rosetta spacecraft is overhead and able to pick up its signals.
“It’s almost certainly still too cold for Philae to recharge its batteries, but it may be able to make contact during the short time it is illuminated twice a day,” Stephan Ulamec, the Philae lander manager, told the Guardian. The rotation of the comet means that Philae has an hour and twenty minutes of sunlight twice a day during which it could call the orbiter.
Mission controllers tried without success to contact Philae in March and April, but the lander was getting so little sunlight that the odds of Philae rousing from its sleep were low.
“In May we now start to have a good chance of making contact, and in June it will be even better. As we get closer and closer to the sun we hope the lander will get more and more power,” Ulamec said. The chances of Philae recharging its batteries will rise until mid-August when the comet passes closest to the sun before speeding back out into the darkness of the distant solar system.
The electronics onboard Philae need to be warmer than -45 Celsius to operate properly, but they may still be too chilly to work, Ulamec said. After 17 May, Rosetta will fall out of position to communicate with Philae until the end of the month, or later in June.
Even the most basic housekeeping data sent back from Philae would be valuable for the Rosetta scientists. The information could help pinpoint the final resting place of the lander, and reveal how much its batteries could recharge as the comet hurtles towards the sun.
Only when mission controllers have an idea of how much power the lander has, can they decide what it should do next. Philae could take simple temperature measurements of the comet surface, snap more pictures of its surroundings or attempt more energy-hungry experiments, such as drilling into the comet surface, to analyse its composition.
“The most demanding instruments require battery charging and that means higher temperatures,” said Ulamec. “But we are preparing them because the worst thing would be for the lander to wake up and we are not ready.”
The £1bn Rosetta mission blasted off from Earth 11 years ago and travelled more than 6bn kilometres on its journey to catch up with the comet, which orbits the sun at 135,000 kilometres an hour. Measurements taken by Rosetta and Philae have given scientists an unprecedented insight into the nature of comets. The discovery last month that the comet has no magnetic field has overturned one of the leading theories of how comets and the precursors of planets formed in the early solar system.