Gaetano Sivo, Vincent Garrel, Rodrigo Carrasco, Markus Hartung, Eduardo Marin,
Vanessa Montes, and Chad Trujillo
News in Adaptive Optics at
Gemini South
Adaptive optics (AO) activities conducted during last year at Gemini
South have not only improved image quality but also resulted in
some exciting recent science (see this issue’s feature article on young
star clusters starting on page 3, and the Science Highlight on page
8) obtained with the Gemini Multi-conjugate adaptive optics System
(GeMS) coupled with the Gemini South Adaptive Optics Imager.
Future AO activities are expected to expand dramatically at Gemini
South once the Natural Guide Star system for GeMS is upgraded and a
more reliable laser is installed.
Adaptive optics systems rely on laser guide star wavefront sensors (LGSWFS) for high-order
measurements of distortions to starlight caused by Earth’s atmosphere. Of course precise
alignment of the system is critical for optimal performance. During the winter (Southern
Hemisphere) telescope shutdown of 2013, the AO group decided to realign the CCD and
lenslets assembly of the LGSWFS; we had calculated that the system’s collimator and lenslets
were offset by 1.8 centimeters, which corresponds to a misconjugation of about 51 (km) on
the sky.
A Puzzling Image Quality Issue with Canopus
Post shutdown, the laser beacon showed a Rayleigh pattern on the LGSWFS that appeared
physically impossible. This first led the AO team to believe that a pixel was swapped inside
a quadcell subaperture used to center the laser beam to a certain spot. Even if this were
the case, the reconfiguration of the WFS introduced unwanted side effects, so the AO team
reverted very quickly to the original configuration, which required two additional days of
work on the telescope.
April 2015
GeminiFocus
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