Figuring out the lander's precise location and orientation will help scientists determine if and when Philae's solar panels might receive enough sunlight, as the comet moves closer to the sun, to recharge its battery and bring the hardy craft back to life for extended science observations. Lodged on its side in a jumble of icy slabs, rocky debris and nearby cliffs, Philae lost power and went into electronic hibernation three days after landing.

While mission managers cannot predict a successful awakening, lead lander scientist Jean-Pierre Bibring is optimistic.

"I think within the team there is no doubt that we will wake up," he told reporters at the American Geophysical Union's Fall meeting in San Francisco. "And the question is OK, in what shape? My suspicion is we'll be in good shape."

The lander faces two major hurdles. Without power, and with most of the spacecraft in shadow, extreme cold could damage internal systems. And without a minimum amount of solar power, Philae's battery cannot charge and its computer system cannot restart. To resume science operations, an additional half-dozen watts will be needed.

"For the electricity, we need to have solar panels with a few watts, typically 5 watts, which is sufficient to reboot the system," Bibring said. "If we want to do (science) we need to have another 5 or 7 watts. So the question is how to get there?"

In April or May, 67P/Churyumov-Gerasimenko will be close enough to the sun to provide the intensity needed, engineers believe, but Philae could wake up earlier if gaps in the local terrain allows additional sunlight to reach its panels.