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Session 85 - Instruments, Databases and Techniques.
Oral session, Thursday, June 13
Playcircle,
The National Solar Observatory is developing an adaptive optics system with the goal to correct atmospheric aberrations in real time and allow for diffraction limited observations of solar features. A key component of the AO system is the wavefront sensor (WFS). The Sun presents unusual problems for wavefront sensing. Unlike the nighttime sky, the Sun does not provide natural, high-contrast point sources, and creation of laser beacons bright enough to be visible against the solar disk poses major technical and operational problems. Wavefront sensing at arbitrary locations on the Sun requires a sensor capable of using the solar granulation as its target. We discuss two approaches to the solar wavefront sensing problem: (a) a modified Shack-Hartmann sensor, which is based on correlation tracking on images formed by an array of subapertures , and (b) an amplitude modulation or spatial filtering procedure, understandable in terms of the classic Foucault knife-edge test. We compare measurements of atmospheric wavefront distortions performed simultaneously with a Shack-Hartmann WFS and a knife-edge WFS. We discuss the performance, limitations and practical considerations of the two wavefront sensor concepts.
