dered our progress on the many programs
scheduled for this semester.
The good news is that, as reported in the
April 2016 issue of GeminiFocus, we have
begun adjusting the queue filling to account for the typical pattern of bad weather
at Gemini South. So, fortunately, the queue
was not overloaded in May as it had been in
the past.
Figure 2 (left).
The new camera cold
head (green mechanism,
at bottom). Above it is
the gate valve baffle,
which is employed during
MOS mask swaps due
to previous thermal
background issues. Photo
Credit: Gabriel Perez/
Gemini/AURA
Figure 3 (right).
The MOS wheel (larger
segmented black wheel,
in front, showing slots for
MOS masks) and Dekker
wheel (smaller black
wheel, behind). Photo
Credit: Gabriel Perez/
Gemini/AURA
12
FLAMINGOS-2
Stand-down Completed
In May, we removed FLAMINGOS-2 from
the Gemini South telescope for a preventative maintenance stand-down. Moving to
dedicated instrument stand-downs ensures
that key resources and the laboratory environment are available without competing
against other important tasks. This has been
an issue during other single annual telescope shutdowns.
A large team of engineers, technicians, and
science staff completed a variety of tasks.
First they replaced the instrument’s three
coldheads (one is shown in Figure 2), which
were approaching the end of their lifetime;
indeed, the coldheads should keep the detector at a selectable temperature, but we
have seen the temperatures gradually in-
GeminiFocus
creasing. Replacing coldheads might sound
easy, but accessing and replacing them requires dismantling the instrument.
Another outstanding issue was addressed
by fixing the On-Instrument WaveFront Sensor used to measure distortions at the instrument imaging plane. Careful testing and
analysis revealed an electronics problem,
which we resolved. We also thoroughly tested all mechanisms, which raised some additional suspicions during the movement of
the Multi-Object Spectroscopy (MOS) wheel
(Figure 3). Further inspection indicated significant wear in some of the ball bearings,
so all were replaced. The team then reassembled and successfully tested the entire
mechanism.
Finally, the instrument was cooled down,
first with liquid nitrogen in the lab, before we
connected it to the helium compressors on
the telescope. We returned FLAMINGOS-2
to the telescope, tested it during the night,
and cleared it for scientific operation. With
this success, a large period of intensive work
came to an end. The instrument should benefit from reliable operations for the coming
semesters, and we can now begin working
on the commissioning of the MOS observing
mode. Weather permitting, we expect to be
commissioning MOS mode in July and August of this year.
July 2016