Phase retrieval analysis of the Hobby-Eberly Telescope primary mirror segment figure error and its implication for wavefront sensingfor the new Wide-Field Upgrade

摘要

Primary mirror segment figure error is potentially deleterious to the wavefront sensing in the new Hobby-Eberly Telescope (HET) Wide-Field Upgrade (WFU). Previous measurements indicated the presence of figure errors including prominent surface astigmatism on the segments, but need a systematic analysis to quantify the amounts. We developed a Phase Retrieval procedure that estimates the surface figure map by applying the iterative transform method to a set of focus-diversed images of a point source formed by the 91 segments of the llm HET primary mirror. In this paper, we discuss this analysis and the implication of the analysis results for wavefront sensing on the upgraded HET.