Post-wide-field-upgrade imaging performance evaluation of the Hobby-Eberly Telescope

The Hobby-Eberly Telescope (HET) is an innovative 10m-class telescope that operates with a fixed altitude segmented spherical primary mirror (M1) while a tracker, located at the top of the telescope, moves the prime-focus spherical aberration corrector (SAC) and instrument package in order to track the sidereal and non-sidereal motions of celestial objects. In 2016, we completed the wide-field upgrade of the telescope, which includes the Wide-Field Corrector (WFC), the tracker, the prime focus instrument package, and all electro-mechanical hardware and telescope control software. Post the upgrade, we have been monitoring the image performance of the telescope through the in-situ metrology. These metrology streams highlight weak spots of the telescope facility in imaging performance and provide quantitative guidance to specific facility repair and/or upgrades to further improve the HET’s overall performance. This paper summarizes our long-range (7yrs) datasets, specific analysis techniques used, and current outcomes of this effort in the context of specific facility improvement and upgrade plans.