Design of the calibration unit for the MOAO demonstrator Raven
Jean-François Lavigne, Frédéric Lamontagne, Min Wang, Marc-André Boucher
Institut national d’optique
The UVic AO Lab in collaboration with HIA and the Subaru telescope is currently designing Raven, a multi-object adaptive optics (MOAO) demonstrator that will be coupled to the Subaru Infrared Camera and Spectrograph (IRCS). Its main goal will be to demonstrate MOAO feasibility on the sky while allowing astronomers to beneficiate from the increased observing efficiency associated with such systems.
Raven will use three natural guide stars (NGS) or two natural guide stars and Subaru laser guide star (LGS) to do the tomographic reconstruction of the atmosphere turbulence. The appropriate correction will then be applied to two science fields that will feed IRCS. The wavelengths between 0.6 and 0.9 µm will be used for the wavefront sensing while the science wavelengths between 0.9 and 2.5 µm will be directed towards IRCS.
INO is currently designing the Raven calibration unit. This sub-system consists in a telescope simulator that will allow aligning Raven components during its integration, testing its AO performances in the laboratory or at the telescope and calibrating the AO system by building the interaction matrix and measuring the non-common path aberrations (NCPA).
The calibration unit will provide a 9x9 grid of broadband (0.6 to 2.5 µm) NGS sources diffraction limited above 1.0 µm and located in a 2.7’ circular FoV. It will allow to vary the NGS sources intensity to emulate stars ranging from R=8 to R=16. An on-axis LGS that can be conjugated to altitudes varying from 85 km to 180 km and intensity ranging from R=5 to R=11 will also be simulated. An on-axis bright white source conjugated to infinity will be installed for the user to see the beam during alignment. The calibration unit will include two deployable phase screens conjugated at altitudes of 5 km and 11 km and a deformable mirror conjugated to the ground.