Adaptive Optics for Extremely Large Telescopes 4 – Conference Proceedings

The implementation of a near-infrared tip-tilt sensor in the Keck I adaptive optics (AO) system is the first of its kind, and represents a substantial step forward in AO technology. Enhanced-TRICK (Tilt Removal with IR Compensation at Keck) is a project built off this implementation which will further improve performance and versatility. Currently the system is capable of using a single star for measuring image motion, but in the off-axis case this may cause elongation in the science image due to tilt anisoplanatism. The near-infrared tip-tilt sensor (NIRTTS) has been designed with the capability of using up to three stars from around the field to correct for elongation. In order for the science object correction to be optimized, the measurements from each star must be weighted based on magnitude and separation from the science object. When weighted optimally the tip-tilt error at the science object will be a minimum. The process for assigning weights is described, and results of performance modeling of the actual systems having multiple tip-tilt stars are presented.