Telescope Shutdowns at Gemini North and South Both Completed
Both the Gemini North and South telescopes have ended their respective shutdowns. The Gemini South telescope was scheduled from August 16 – 25, which occurred as planned. The Gemini North telescope shutdown was moved from October to August 10 – 31, which is reflected in the updated schedule.
Gemini South Shutdown
The Gemini South staff did an outstanding job during the annual shutdown of the telescope, which included preventive maintenance of all mechanisms, including the Acquisition and Guidance unit (A&G), and the Gemini Multi-Object Spectrograph (GMOS) On Instrument Wave Front Sensor (OIWFS). Additional accelerometers were also fitted inside of the A&G to enhance vibration monitoring capabilities.
After thorough investigation of GMOS-South on the telescope, it was concluded that the grounding scheme in the cabling was the culprit for the noise pattern on the OIWS. The cabling was improved, the grounding schemes were documented for future reference, and final testing should be completed by the time this blog is published.
To improve the chiller operational performance and energy efficiency, additional valves were added to provide a best way to control the cooling circuits of the different systems. It was necessary to boost a complete power shutdown to replace a 200 Amp breaker that was failing intermittently. Information Technology Services (ITS), as well as Gemini and National Optical Astronomy Observatory (NOAO) electricians, made a good team and were able to complete this task quickly without any setbacks.
Finally, preventive maintenance on all mechanisms is complete, which included replacing a few gear boxes, and extensive repeatability tests to confirm correct functions of all mechanisms. The science fold was fine tuned and the staff fixed a problem with one of the encoder tapes on the linear slide from the science fold.
With Michiel Van Der Hoeven, Gemini South Head of Engineering Operations
Gemini North Shutdown
As mentioned above, the Gemini North telescope shutdown, originally planned for October, was moved to August. This was to address the issue of a drive shaft bearing failure on one of the Bottom Shutter gearboxes on the 2X/2Y side, which was noticed on July 28, 2016. The repair project was then planned, scheduled, and implemented from August 10 through August 30, 2016.
The biggest task of the shutdown was the Bottom Shutter 2X/2Y Gearbox Repair Project. Gemini North staff finished removing the old 2X/2Y drive box and assembling the new 2X/2Y drive box. The newly assembled 2X/2Y drive box was successfully installed into the Bottom Shutter with the chains adjusted, and the Enclosure Control System (ECS) was tested before handing over the telescope for night operations on the night of August 30, 2016. Due to a repair needed on the other Bottom Shutter Drive Box 1W/1Z, it was decided to leave the bottom shutter locked out in park position for continued night operations, which will be addressed at Gemini North at a later shutdown scheduled during 2017. The 2X/2Y repair project was determined a success by meeting the objectives of completing the repair by the planned schedule and providing Gemini with a fully functional drive box on the 2X/2Y side.
Other tasks during the shutdown include instrument maintenance on GMOS-North and a filter exchange in NIRI. The Acquisition and Guiding (A&G) unit was removed and work was done to the Peripheral Wave Front Sensor 2 (PWFS2). The optics were cleaned, and then the modules were assembled and placed into the Instrument Support Structure (ISS) and electronically connected. The GMOS-North filters and gratings were also cleaned.
The day crew at Gemini North has done an excellent job during the unexpected shutdown.
Joe D’Amato, Administrative Assistant – Maunakea and John White, Senior Instrumentation Engineer.