This award will support the construction of a prototype instrument for real-time adaptive compensation of atmospherically induced wavefront distortion. Optimized for low-order corrections on a 4-m class telescope, the instrument is expected to produce images with an angular resolution close to the diffraction limit in the near infrared under average seeing conditions, and occasionally in the visible under good seeing conditions. It will require a reference star brighter than mag 17 within a typically one arc-minute field of view to sense the wavefront errors allowing compensation to be achieved over most of the sky. The instrument is based on the novel concept of curvature sensing and compensation and will use an array of 13 photon counting avalanche photodiodes to sense the wavefront. The goal of this instrument is to demonstrate that such a performance can be achieved and to serve as a basis for the development of adaptive optics on existing and future ground- based telescopes. It will provide an angular resolution comparable to that of the Hubble Space Telescope with a larger collecting power, and therefore will have a considerable impact on almost every field in astronomy especially for narrow-band imaging and spectroscopic observations.
