Craig,  from INSTRM-466 it says "We currently convert Gen2 keywords into FITS header sections inside the gen2Actor". I am not clear how to retrieve FITS information from gen2actor?

McsCmd.py:_constructHeader() does the work of building the MCS FITS header. I suspect we will leave that until after September, but the intent of INSTRM-466 is to get rid of everything above the call to self._getInstHeader(). INSTRM-466 would make an actorkeys dictionary like the one for meb.py.

Sorry that I didn't read the new MCS code but it's faster to ask questions here. I suppose that fps can get telescope rotation by calling gatherHeaderCards in actorcore.utility.fits from "gen2" actorkeys model. And for each observation, this could be done only for once since this angle should be fixed during the entire period of each observation.

For now, fps take the rotation angle from telescope. This issue is solved.