Laser Operations at the 8-10m class telescopes Gemini, Keck and the VLT: lessons learned, old and new challenges

Laser Guide Star (LGS) assisted Adaptive Optics routine operations have commenced at three of the major astronomical observatories, in 2004 (Keck) and 2006 (VLT and Gemini) respectively. Subaru is also on the verge of putting its LGS facility into operations. In this paper we concentrate on the operational aspect of the laser facilities: we discuss common problems such as weather constraints, beam collisions, aircraft avoidance and optimal telescope scheduling. We highlight important differences between the observatories, especially in view of the valuable lessons learnt. While it is true that the three observatories have made quick progress and achieved important scientific results during the first years of operations, there is much room left for improvement in terms of the efficiency that can be obtained on sky. We compare and contrast the more recently implemented LGS systems of VLT and Gemini operated in service and queue modes to the more mature LGS operation at Keck that employs classical PI scheduled observing.