With the batteries running down on the Philae lander, ESA decided to activate MUPUS (multi-purpose sensors) -- which hammered the penetrator into the ground. This was a risky manoeuvre, as the lander is not tethered to the comet -- but the lander did not shift position. They have also activated the drill to collect samples for COSAC (the chemistry instruments). APXS (alpha particle x-ray spectrometer) was also activated. MUPUS and APXS have already returned data.
And then... Rosetta went below the horizon of the comet and contact with the lander was lost. (This was an expected event). Radio contact should be reestablished around midnight CET.. if the batteries hold, which they might not. The commands to put Philae into a low energy mode were not successfully downloaded to the lander, so the batteries are a major worry now.
The precise position of the lander still has not been determined, but it is thought to be near site 'B', a conspicuous crater on the smaller "lobe" of the comet. There are high res images still to be downloaded from the Rosetta orbiter that may help with the search.
If the batteries still have energy and contact can be reestablished, tonight an attempt may be made to move the lander out of "the hole" it is in, or at least to shift it enough to get better illumination of the solar panels.
But the COSAC data -- the complex organic chemistry package -- which is a major goal of this mission, will depend on reestablishing contact tonight.
It's all down to the batteries now. Let us pray to the gods of batteries.