Date of Award
Doctor of Philosophy in Applied Physics - (Ph.D.)
Federated Physics Department
T. R. Rimmele
Philip R. Goode
Carsten J. Denker
Adaptive optics (AG) systems provide partial correction to wavefront distortions introduced by the Earth's atmosphere. They have become an essential tool to obtain diffraction-limited observations from ground-based telescopes. However, the AG correction is only partial and post-processing with a good estimate of the point spread function (PSF) is required.
PSF estimates are impossible to measure directly during solar observations due to the lack of point sources in the field-of-view. Moreover, the highly variable day-time seeing conditions require the estimated PSF to be simultaneous with the captured image. A method is presented to estimate the long-exposure PSF of AG-corrected solar observations using the AG control loop data. The wavefront sensor and the deformable mirror data produced by the AG system during normal operation provide enough information to estimate the long-exposure PSE. Using this method, each individual AG-corrected image can be deconvolved with its own estimated PSF.
An attempt was made to verify the accuracy of the method by observing the star Sirius. The AG system successfully produced AG-corrected star images, which provide direct PSF measurements that can be compared to the estimated PSF. However, the poor performance of the AG system under low light levels, for which it was not designed, led to large uncertainties in the estimated PSFs.
The PSF estimation method was tested on real solar observations, where an estimation of the AG-corrected PSF is normally difficult. The observations were deconvolved with the estimated PSFs, producing significantly improved quantitative measurements and scientific data. A measurement of the performance of the solar AG during different seeing conditions was obtained for the first time from these observations.
Marino, Jose, "Long exposure point spread function estimation from solar adaptive optics loop data" (2007). Dissertations. 817.