A Shack-Hartmann wavefront sensor projected onto the sky with reduced focal anisoplanatism

A method for producing a laser guide star wavefront sensor for adaptive optics with reduced focal anisoplanatism is presented. A theoretical analysis and numerical simulations have been carried out and the results are presented. The technique, named SPLASH (Sky-Projected Laser Array Shack-Hartmann), is shown to suffer considerably less from focal anisoplanatism than a conventional laser guide star system. The method is potentially suitable for large telescope apertures (∼ 8 m), and possibly for extremely large telescopes.