The most recent imaging search by the overflying Rosetta “mothership” can find no trace of the probe.
Philae touched down on 67P/Churyumov-Gerasimenko on 12 November, returning a swathe of data before going silent when its battery ran flat.
European Space Agency scientists say they are now waiting on Philae itself to reveal its position when it garners enough power to call home.
Researchers have a pretty good idea of where the robot should be, but pinpointing its exact location is tricky.
On touchdown, Philae bounced twice before coming to rest in a dark ditch.
This much is clear from the pictures it took of its surroundings. And this location, the mission team believes, is just off the top of the “head” of the duck-shaped comet.
The orbiting Rosetta satellite photographed this general location on 12, 13 and 14 December, with each image then scanned by eye for any bright pixels that might be Philae. But no positive detection has yet been made.
As 67P moves closer to the Sun, lighting conditions for the robot should improve, allowing its solar cells to recharge the battery system.
The latest assessment suggests communications could be re-established in the May/June timeframe, with Philae distributing enough electricity to its instruments to resume operations around September.
This would be at perihelion – the time when the comet is closest to the Sun (185 million km away) and at its most active.
Scientists continue to pore over the data Philae managed to send back before going into hibernation.
Some of the results – together with ongoing Rosetta observations – were reported at the recent American Geophysical Union meeting in San Francisco.
Highlights include a clearer idea of the nature of the comet’s surface. Researchers say this appears to be covered in many places by a soft, dusty “soil” about 15-20cm in depth.
Underneath this is a very hard layer, which is thought to be mainly sintered ice.