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);
Andy Adamson (Gemini, in attendance);
Bryan Miller (Gemini, in attendance); John
Blakeslee (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-
tive optics observing throughout the semes-
ter (Figure 1).
The Next Generation Natural
Guide Star Sensor for GeMS
Gemini-South’s Multi-conjugate adaptive
optics System provides for an adaptive op-
tics (AO) corrected field of about one arc-
minute. To achieve this important capabil-
ity, the system relies on a constellation of
five laser guide stars and up to three natural
guide stars in order to sense and correct for
atmospheric turbulence. The original design
of the natural guide star sensor has been in
operation now for several years. It is based
around three mechanical probes picking up
stars in the field. Each probe channels the
light onto optical fibers leading to avalanche
photodiodes for fast centroiding. Unfortu-
nately, the sensitivity of this system leaves
much to be desired, and the mechanical ar-
rangement is complex in operation.
Therefore, some years ago, Gemini entered
into a collaboration with the Australian Na-
tional University (ANU) to develop a better
system designed around the now available
high-speed Electron Multiplying (EM) CCD
cameras. Using an EM CCD imager will re-
sult in much improved sensitivity. The mov-
ing probes will no longer be necessary, as
the full patrol field will be imaged onto the
CCD, while regions of interest around the se-
lected stars will be read out at high speed
to provide centroiding information to the
Figure 1.
Gemini Science
Operations Specialist
Michael Hoenig (back)
and Gemini Senior
Laser Technician Jeff
Donahue discussing
LGS operations for the
TOPTICA laser in the
Gemini Base Facility
Control Room in Hilo.
Credit: Jeff Donahue
April 2019
GeminiFocus
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