CANARY: the On-Sky NGS/LGS MOAO Demonstrator for EAGLE

摘要

EAGLE is a multi-object 3D spectroscopy instrument currently under design for the 42-metre European Extremely LargeTelescope (E-ELT). Precise requirements are still being developed, but it is clear that EAGLE will require (-100 x 100actuator) adaptive optics correction of —20 - 60 spectroscopic subfields distributed across a —5 arcminute diameter fieldof view. It is very likely that LGS will be required to provide wavefront sensing with the necessary sky coverage. Twoalternative adaptive optics implementations are being considered, one of which is Multi-Object Adaptive Optics(MOAO). In this scheme, wavefront tomography is performed using a set of LGS and NGS in either a completely open-loop manner, or in a configuration that is only closed-loop with respect to only one DM, probably the adaptive M4 of theE-ELT. The fine wavefront correction required for each subfield is then applied in a completely open-loop fashion byindependent DMs within each separate optical relay. The novelty of this scheme is such that on-sky demonstration isrequired prior to final construction of an E-ELT instrument. The CANARY project will implement a single channel of anMOAO system on the 4.2m William Herschel Telescope. This will be a comprehensive demonstration, which will bephased to include pure NGS, low-order NGS-LGS and high-order woofer-tweeter NGS-LGS configurations. The LGSsused for these demonstrations will be Rayleigh systems, where the variable range-gate height and extension can be usedto simulate many of the LGS effects on the E-ELT. We describe the requirements for the various phases of MOAOdemonstration, the corresponding CANARY configurations and capabilities and the current conceptual designs of thevarious subsystems.