Gemini North Shutdown Plans

One of the two-ton drive boxes suspended during a prior shutdown.

Gemini North is now in a major shutdown to resolve the shutter issues that have affected the telescope since 2014. Gemini’s lower and upper shutters, which weigh 9 and 20 tons respectively, crawl along stationary chains located at either side of the shutter, using powered “drive boxes” (one of which is pictured here). In the aftermath of the failures in late 2014 and early 2015, the drive boxes were significantly redesigned and have been tested at Gemini South; but it was also clear that differential stretching of the chains had played a role in the failures, requiring the chains to also be replaced. This work requires a long series of coordinated activities. Extraction of the chains requires hiring the largest crane available on the island of Hawai‘i and, since the drive boxes themselves weigh 2 tons, extracting them from the shutter and bringing them to ground level (and back up) can best be described as non-trivial. Currently the schedule calls for the work to run from 10-July to 25-August.