  LINC--NIRVANA (LN) is an MCAO module currently mounted on the Rear Bent
Gregorian focus of the Large Binocular Telescope (LBT). It mounts a camera
originally designed to realize the interferometric imaging focal station of the
telescopes. LN follows the LBT binocular strategy having two twin channels: a
double Layer Oriented Multi-Conjugate Adaptive Optics system assisting the two
arms, supplies high order wave-front correction. In order to counterbalance the
field rotation, a mechanical derotation is applied for the two ground
wave-front sensors, and an optical (K-mirror) one for the two high layers
sensors, fixing the positions of the focal planes with respect to the pyramids
aboard the wavefront sensors. The derotation introduces a pupil images rotation
on the wavefront sensors, changing the projection of the deformable mirrors on
the sensor consequently.
