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 .
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 13 ), 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 increasing . 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
January 2017 | 2016 Year in Review
all mechanisms , which raised some additional suspicions during the movement of the Multi-Object Spectroscopy ( MOS ) wheel ( Figure 14 ). 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 FLAMIN- GOS-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 .
Repairing the Gemini North Wind Blind
Both Gemini domes are equipped with a three-segment wind blind , which is deployed by moving the lower shutter to shield the telescope structure from wind coming from the direction of the open slit ( Figure 15 ). Gemini North ’ s wind blind has caused concern since early 2015 , when we found excess wear on the track and roller system during regular maintenance . Considered a serious problem , we disconnected it in the
GeminiFocus
Figure 13 ( 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 . Image credit : Gabriel Perez / Gemini / AURA
Figure 14 ( right ). The MOS wheel ( larger segmented black wheel , in front , showing slots for MOS masks ) and Dekker wheel ( smaller black wheel , behind ). Image credit : Gabriel Perez / Gemini / AURA
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