The ESA sent out the Rosetta spacecraft years ago with the mission of meeting up with the Comet 67P/Churyumov-Gerasimenko. The mission has gone perfectly so far, but has now hit a snag. The Philae lander was sent down to the surface of the comet and worked continuously for 54 hours sending data back to Earth. However, the battery went dead since then Rosetta has been unable to establish contact with the lander for the last eight days.
The scientists are still hoping that contact can be made and there are numerous reasons why Philae may not have made contact yet. Those reasons include possibilities such as the lander being too cold to wake up. Philae may also not have collected the power resources it needs to send a signal to the Rosetta orbiter.
The team controlling the spacecraft switched off the communication unit on the orbiter on March 20. Scientists are now working on devising when the next favorable alignment between the Rosetta spacecraft and the lander will be so they can switch the communications gear on again and attempt to establish contact.
The lander needs internal temperatures above -45 degrees Celsius and at least five watts of power to turn on automatically. The lander can’t send signals back to Earth via Rosetta until it has 19 watts of power stored. The next attempt to contact Philae will be made in April.