TMT Laser Guide Star Facility preliminary design

The TMT Laser Guide Star Facility (LGSF) system is responsible for generating the artificial guide stars in the mesospheric sodium layer with the brightness, beam quality and asterism geometries required by both the first light AO system and future AO instruments. It includes the sodium lasers mounted on the elevation structure, the beam transfer optics to transport the beams up to the telescope top end, and the formatting and launching optics to project the required laser guide star asterism to the sky using a center launch telescope. In this paper, we will present the LGSF preliminary design including the design trade-offs, the optical, mechanical, electronics and software design, as well as the modeling activities.