Gemini Mauna Kea laser guide star system

We discuss the design of the laser guide star system to be implemented with ALTAIR, the Gemini North adaptive optics system. We give an overview of the sodium physics in order to understand why some lasers are more efficient than others to produce bright artificial stars. We present some simulation results which set the laser output power requirement when launching a perfect beam to the sky. Preliminary designs for the beam transfer optics, the laser launch telescope and the safety systems are also presented.