GeminiFocus July 2019 | Page 22

Gemini staff contributions
News for Users
A technical intervention with GMOS-South leads to
promising results. The Gemini Planet Imager is in the lab to
fix a problem with its Micro-Electrical Mechanical System
deformable mirror. Gemini's participation in the 2019 CASCA
meeting in Montréal, Canada, helped many users. Finally,
Gemini North's primary mirror is ready to receive a fresh
coating during a planned shutdown starting in late July.
Figure 1.
Gemini North engineer
John White working
on the CCD focal plane
array just prior to
replacing the electronics
board.
Credit: Luc Boucher
GMOS-South CCD Intervention
The Gemini Multi-Object Spectrograph (GMOS) at Gemini
South has, for some time, suffered from instabilities in the
charge-coupled device (CCD) readout. Since the installation
of the Hamamatsu CCDs, they have been performing sub-
optimally. In particular, we have seen instances where the
charge transfer efficiency became too large, causing smear-
ing on the images, which affects the popular Nod & Shuffle
mode of the instrument. We have been planning to tackle
this issue by changing the existing electronics board inside
the cryostat with one of a better design. This design has
been proven to work for the GMOS instrument at Gemini
North, which does not experience the same smearing ef-
fect. The critical and very sensitive intervention was carried
out in June. The technical intervention went very well, and
the lab tests quickly showed very promising results. GMOS-
S was put back in normal operation and the effect of charge
smearing has not been seen again. The CCD array performs
to specification.
July 2019
GeminiFocus
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