The field stops are extremely difficult to
reach, as they are enclosed in a mechanical set positioned between two lenses, a
consequence of the compact design of the
Canopus optical bench. Rather than adjust
the field stops, the other option we identified was to realign the CCD behind each
LGSWFS and the calibration source. Doing
this, we realized, would restore alignment
to the calibration source, the field stops,
and the CCDs.
of the sky around the Galactic poles would
be available with at least one guide star.
A More Reliable Laser
The laser currently used in Gemini South
is a 50 Watt (W) sodium laser created by
non-linearly combining two infrared beams
inside a crystal. Since its infancy, the laser
Figure 3.
Post shutdown
GeMS/GSAOI image.
Figure 4.
Performance results
achieved using GeMS/
GSAOI. ~75 mas in the
whole field-of-view.
We proceeded with this option because
(1) it was the least invasive, and (2) the
LGSWFS CCDs were the easiest elements
to move. We then remounted Canopus
on the telescope and waited for the telescope shutdown to end.
During the first post shutdown GeMS observing run (September 2014), we confirmed that the realignment of the CCDs
had indeed removed the elongation issue
(Figure 3). Since then, several successful
science runs with the system have produced excellent results. Figure 4 illustrates
the level of performance that the system
can now provide.
Future Plans for GeMS
A New Natural Guide Star
WFS System
The AO team at Gemini, with collaborators from the Australian National
University, is currently working on
upgrading the Natural Guide Star
Wave Front Sensor (NGSWFS) system.
This upgrade will allow the system
to u ͔