to directly work with many users who had
Phase I, Phase II, and data reduction ques-
tions. Scot Kleinman also presented a talk
about the future role of Gemini in the Time-
Domain Astronomy era. We thank McGill
University for organizing a successful meet-
ing, and we look forward to meeting with ev-
eryone again at York University, in Toronto,
next year.
Gemini North Primary Coating
During Shutdown
The Gemini North primary mirror will get a
new coat in the course of an extended mid-
year shutdown, which is scheduled to start
on July 23rd. The same coating recipe will
be used as is currently on the mirror, which
comprises four distinct layers deposited
by sputtering different magnetron targets.
Closest to the glass substrate, a 65-Ångstrom
(Å)-thick layer of nickel chromium (NiCr) acts
as an adhesive layer between the glass and
the overlying reflective silver layer. The silver
is sputtered onto the NiCr, at a much greater
thickness of 1100 Å. Next a wafer-thin layer
of NiCr is sputtered on top of the silver; with
a thickness of only 6 Å. Finally, an overcoat
of silicon nitride is applied by sputtering a
boron doped silicon target with nitrogen
process gas. The thin NiCr appears to facili-
tate the growth of a dense and protective
silicon nitride layer, and slows any corrosion.
The current coating has lasted well, but at
six years since the last coating, it’s time to
replace it.
Other jobs in the shutdown include replac-
ing and upgrading the helium supply hoses
in the Cassegrain wrap, replacing the glycol
coolant hoses, and some instrumentation
work, including dealing with a bubble in
the oil interfaces in the Gemini Multi-Object
Spectrograph lens system.
January 2020 / 2019 Year in Review
APRIL 2019
GEMMA-TDA Advisory Group
Assembled
Guided by a Gemini Science and Technology
Advisory Committee action regarding time-
domain astronomy (TDA) and multi-mes-
senger follow-up, we have assembled a rep-
resentative team of astronomers from across
the Partnership to advise us on our devel-
oping plan for TDA. This advisory group,
chaired by Abhijit Saha of the National Opti-
cal Astronomy Observatory (NOAO), has had
two meetings as of early March.
The members are: Abhijit Saha (US; NOAO) -
Chair; Andres Jordan (CL); David Sand (US);
Basilio Santiago (BR); Meg Schwamb (Gemi-
ni); Federica Bianco (US); Myungshin Im (KR);
Maria Drout (CA); Craig Heinke (CA); Victoria
Alonso (AR); Alexander Vanderhorst (US);
and Andy Adamson, Bryan Miller, and John
Blakeslee (all Gemini, in attendance).
Not all of the members of this time-domain
advisory group work on time-domain sci-
ence; the mission of the group includes
protecting the completion of non-TDA pro-
grams in the coming Large Synoptic Survey
Telescope era when we expect to have an
increased number of Target of Opportunity
proposals. We are grateful to Abi and the
group for helpful commentary to date.
TOPTICA Laser:
Available Every Night!
With a fully commissioned TOPTICA laser,
we are back in operation for Laser Guide
Star (LGS) mode at Gemini North. The 19A
semester will be a “transition” period from
scheduled laser blocks to a fully-integrated
LGS queue operations model. This will al-
low for LGS programs to be observed on any
night when conditions allow, giving Gemini
Principal Investigators access to LGS adap-
GeminiFocus
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