Figure 2:
Gemini South
time allocations
by instrument in
Semester 2013B.
A Busy Semester at Gemini South
Looking forward, Gemini South operations
(assuming all goes well) should see one of the
most event-filled semesters in recent memory. On the horizon is a maintenance shutdown at the start of the semester, the delivery
of the Gemini Planet Imager (GPI) and its early
commissioning, the delivery of the GMOS-S
Hamamatsu CCDs, GeMS’s continued transition into science operations, and the first full
semester of FLAMINGOS-2 operations. While
not all of these items are yet firm, as work
continues in the lab on both GPI and the CCD
package, the schedule is being set up to accommodate all of these activities.
Telescope and Dome Engineering
Figure 3:
Part of the Gemini South
top-end system, in the
lab during installation
of the new micro-E
sensors. The +Y sensor
is installed behind the
yellow plate on a black
metal piece, just inside
the upper ring next to
the “+Y” label.
24
be removed (Figure 3) and thus requiring a
shutdown of at least a week. What ensued is
what you might expect. We took a detailed
look at the likelihood of complete failure,
which would leave us unable to guide, and
of how detectable this would be in advance.
We also weighed this against the disruption
which would be caused by an unplanned
shutdown, possibly in the middle of a GeMS
or FLAMINGOS-2 commissioning or System
Verification run. We worked it out such that
the output could be monitored well enough
to continue into semester 13A, but a number
of possible shutdown points were identified
in case deterioration accelerated or other opportunities emerged. In the end, a FLAMINGOS-2 delay produced an open schedule
week in March, and it was decided that we
had to go for it.
Work started in late March, but almost immediately we were hit with a failure of the main
transformer which supplies electricity to the
whole of Cerro Pachón. The rest of the period
is not one which anyone would wish to ever
repeat, but the engineering team did a fantastic job and both completed the micro-E
replacement and kept nighttime operations
going on generators – albeit with a couple of
hiccups early on when the main Gemini diesel
generator suffered a mechanical failure and
required supplementing with a hired unit.
Replacing Top-end Position
Sensors at Gemini South
Late last year it was determined
that the light output from two
of our top-end mirror position
sensors (known as “micro-E”s)
was failing, indicating that the
sensors were nearing the end
of their lifetime almost a year
earlier than expected. The process of replacing these sensors is highly invasive, requiring the entire top-end unit to
GeminiFocus
July2013