The acquisition, guiding, and wavefront sensing system for the Giant Magellan Telescope

The Acquisition Guiding and Wavefront Sensing System (AGWS) is responsible for making the measurements required to keep the optics of the seven-segment GMT coaligned, phased, pointing in the correct direction, and conforming to the correct mirror shape. The AGWS consists of four identical probes that patrol the outer parts of the GMT field of view. Each probe is comprised of two channels. The visible channel contains optics that can provide high-speed full aperture guiding, segment guiding, or Shack-Hartmann wavefront sensing feeding an EMCCD camera. In natural seeing operations, these probes feed the GMT active optics system. In ground layer AO mode, they are the primary wavefront sensors. The second channel, used for phasing the seven segments in diffraction limited operation, contains J-band dispersed fringe sensor optics feeding a SAPHIRA IR e-APD array. We present the system architecture, and an overview of requirements, optical, mechanical and electrical designs.