As of Period 78 NAOS can be fed by an artificial sodium laser guidestar (LGS) which is positioned on sky on top of the science target allowing for high-order AO corrections.
A natural guide star (NGS) is still required to correct for thetip-tilt motions, which are not sensed by the LGS. The NGS has to be inthe V magnitude range 12-17 and can be as far away as 40" from the science target, however, with decreasing performance with increasing distance. At 40" distance about half the Strehl ratio is achieved ascompared to having the NGS on-axis with the LGS.
At the time of writing the Call for Proposal, the LGS mode of NAOS has just started its commissioning and little is known about the actual performance. The use of the LGS mode is for the time being recommended only for science programs, which can take advantage of moderate Strehl ratios ("seeing enhancements") to achieve their scientific goals.
The users are encouraged to frequently check the instrument web page for updates on the LGS performances. In Period 78 the LGS mode of NAOS is only available in Service Mode.
Chopping with counter chopping is offered under restricted conditions.
Please check this page for more information.Chopping with counter-chopping is NOT offered together with the LGS-mode.
The constraints on the spectroscopic acquisition has been released.
It is now possible to acquire also with the S/L54 cameras (but forcing a neutral density in the path).
The 'new' "AstroCoro" template is now offered in service mode as well.