Philae lander, the first man-made spacecraft to make it on the surface of a comet, touched down on comet 67P/Churyumov-Gerasimenko in November last year. A bouncy landing, however, has left it stranded in an area where it could not receive enough sunlight. The probe was able to carry out some experiments but it eventually ran out of power.
Scientists, nevertheless, were optimistic that the Philae could wake up once again as the comet gets closer to the sun, and receive enough heat and sunlight. This opportunity could happen soon. The first possibility to receive a signal from the lander has come, so Rosetta orbiter's communication unit will be switched on to contact Philae.
Since March 12, scientists from the European Space Agency (ESA) started to listen for signals that would indicate that the probe has survived. Philae could begin sending data from the surface of Comet 67P once enough sunlight charges its solar panels and improves its battery power.
Comet 67P, along with Rosetta and Philae, are currently 320 million kilometers, or 198.8 million miles, from the sun. Lander Project Manager Stephan Ulamec said that at this proximity, the lander gets twice as much energy from the sun compared with what it was able to receive late last year.
Ulamec admitted that may still be too cold for Philae to wake up, but scientists believe that waking up Philae is worth trying. He added that the prospect improves with each passing day.
For Philae to start working again, it must meet several requirements. Its interior, for instance, should be at least -45ºC before it can wake up from its sleep.
The lander should also be able to produce at least 5.5 watts using its solar panels to wake up from its slumber. Once it meets these conditions, the Philae will turn on, heat up further and will try to charge its battery. Since it soft landed on the comet, the lander has been using all available solar energy in order to heat up.
Once Philae wakes up, it will switch on its receiver every half an hour and listen for a signal from the Rosetta orbiter, and this can be done even when it is in a very low power state.
"At this time, we do not yet know that the lander is awake," said Koen Geurts from the DLR Control Center. "To send us an answer, Philae must also turn its transmitter - and that requires additional power."
