Philae Idled, Batteries Drained; Needs Luck, Sunshine to Awake

Contact with the Philae lander was lost at 6:36 p.m. (CST) this evening, November 14th, before the normal loss of signal when Rosetta orbits below the lander’s horizon. Without sunlight to juice up its solar panels and recharge the its batteries, the craft will remain in “idle mode” – maybe for a long time. All its instruments and most systems on board have been shut down. 

“Prior to falling silent, the lander was able to transmit all science data gathered during the First Science Sequence,” says DLR’s Stephan Ulamec, Lander manager. All of the science instruments were deployed, including the instruments that required mechanical movement, such as APXS, MUPUS, and the drill, which is designed to deliver samples to the PTOLEMY and COSAC instruments inside the lander.

No contact will be possible unless maneuvers by controllers on the ground nudge Philae back into a sunnier spot. On its third and final landing, it unfortunately came to rest in the shadow of one of the comet’s many cliffs. Contrary to earlier reports (or speculations), Valentina Lommatsch from the German Aerospace Center explained that all three of Philae’s legs are on the ground. But the lander appears to be tipped up at an angle because one of the scenes from the panorama (below) shows mostly sky.

This evening, mission controllers sent commands to rotate the lander’s main body to which the solar panels are fixed. This may have exposed more panel area to sunlight, but we won’t know until Saturday morning (Nov. 15) at 4 a.m. (CST) when the Rosetta orbiter has another opportunity to listen for Philae’s signal.

The batteries were designed to power the probe for about 55 hours. Had Philae landed upright in the targeted region, its solar panels would have been out in the open and soaking up the sunlight needed for multiple recharges. There’s also the possibility that months from now, as seasons progress and illumination changes on the comet, that the Sun will rise again over the probe.

We may hear from the lander again or not. But if not, all the science instruments were deployed in the first two days of landing and data has been received.

* Update 7 a.m. (CST) November 15: A bit of good news! Rosetta has regained contact with Philae during the overnight communication pass, confirming that the lander still has power. The bad news is that the batteries will be completely drained sometime today.