As Brian Carcich noted, you will need to learn and use SPICE. There is a bit of a learning curve, but it is well worth it. You can find the latest kernel [here][1]. The latest `CATT_*.BC` file in that directory has the detailed orientation and rotation information for the comet. It looks like a new one is uploaded every three or four days. Look at the [readme][2] there for some information on how to use it.


  [1]: http://naif.jpl.nasa.gov/pub/naif/ROSETTA/kernels/ck/
  [2]: http://naif.jpl.nasa.gov/pub/naif/ROSETTA/kernels/ck/aareadme.txt