Extreme Adaptive Optics using an off-axis subaperture on a ground-based telescope

摘要

The next generation of adaptive optics (AO) systems, often referred to as extreme adaptive optics (ExAO), will use higher numbers of actuators to achieve wavefront correction levels below 100 nm, and so enable a host of new observations such as high-contrast coronagraphy. However, the number of potential coronagraph types is increasing rapidly, and selection of the most advantageous coronagraph is subject to many factors. Here it is pointed out that experiments in the ExAO regime can already be carried out with existing hardware, by using a well-corrected subaperture on an existing telescope. For example, by magnifying a 1.5 m diameter off-axis subaperture onto the AO system's deformable mirror (DM) on the Palomar Hale telescope, we have recently achieved stellar Strehl ratios as high as 92% to 94%, corresponding to wavefront errors of 85 - 100 nm. Using this approach, a wide variety of ExaO experiments can thus be carried out well before "next generation" ExAO systems are deployed on large telescopes. The potential experiments include infrared ExAO imaging and performance optimization, a comparison of coronagraphic approaches in the ExAO regime, visible wavelength AO, and predictive AO.