SHARK-NIR: challenges and solutions of a high contrast imager alignment

SHARK-NIR is a high contrast camera for the LBT, working in Y, J and H bands. It has been conceived and designed to fully exploit the high Strehl adaptive optics correction delivered by the FLAO module, which is being upgraded to SOUL, and will implement different coronagraphic techniques, with contrast as high as 10-6 up to 65 mas from the star. To maximize the achievable contrast, SHARK-NIR has a couple of peculiar features, namely a fast internal TT loop to minimize the residual jitter and a local NCPA correction, performed through a DM inside the instrument itself. Other than high-contrast imaging, SHARK-NIR also has spectroscopic capabilities, with low and medium resolution, and its relatively wide Field of View (18 x 18 arcsec) makes it accessible to other scientific targets, such as galactic jets and disks, as well as extra-galactic cases. Sharing the focal station with another instrument at LBT (LBTI), the design has been kept very compact. This has been achieved through the use of 4 Off-Axis Parabolic mirrors (OAPs) and three flat folding mirrors able to provide two pupil planes and two focal planes required by the coronagraphic techniques implemented. A mixed optical-mechanical alignment procedure has been identified and extensively simulated using ray-tracing software, demonstrating that the proposed technique converges to the required performance. We report here about the SHARK-NIR lesson learned and status in the frame of the Assembly, Integration and Verification phase (AIV), delayed due to the covid 19 emergency, which is going to finish in first half of 2021 and bringing in this way the first photons to the instrument by the end of 2021.