Imaka: a Lagrange invariant of ELTs
Résumé
The IMAKA project is a ground layer corrected wide field visible imager proposed for CFHT. It consists of three processes or components: The dome and local turbulence will be controlled by ventilation; the remaining ground layer turbulence will be corrected by a GLAO system and the free atmosphere seeing will be locally reduced by using an Orthogonal Transfer CCD to correct for tip-tilt within the isokinetic angle of field stars. In designing the AO system, whether based on an adaptive secondary mirror or using pupil relay optics, it becomes apparent that the conjugation of the deformable mirror is a difficult constraint to achieve given the large field. It turns out this problem is not isolated to IMAKA, because the Lagrange Invariant for our project is in the same range as that of EAGLE on the E-ELT for example. The effects of tilting the deformable mirror with respect to the pupil or compensating for misconjugation of an adaptive secondary mirror using a tomographic reconstructor have been investigated using Monte-Carlo simulation codes, including our code developed specifically for GLAO simulations. We report on quantitative results from IMAKA simulations for a variety of realistic turbulence conditions for each topical scheme, and allude to how these results are applicable to ELTs' adaptive optics.