The alignment and phasing system for the Thirty Meter Telescope

The Thirty Meter Telescope (TMT) is a collaborative project between the California Institute of Technology (CIT), the University of California (UC), the Association of Universities for Research in Astronomy (AURA), and the Association of Canadian Universities for Research in Astronomy (ACURA). The Alignment and Phasing System (APS) for the Thirty Meter Telescope will be a Shack-Hartmann type camera that will provide a variety of measurements for telescope alignment, including segment tip/tilt and piston, segment figure, secondary and tertiary figure, and overall primary/secondary/tertiary alignment. The APS will be modeled after the Phasing Camera System (PCS), which performed most, but not all, of these tasks for the Keck Telescopes. We describe the functions of the APS, including a novel supplemental approach to measuring and adjusting the segment figures, which treats the segment aberrations as global variables.