Shake, Rattle and Roll

The earthquake that rumbled across the Big Island on October 15 has impacted Gemini North, Canada's largest optical telescope. All of the telescopes on Mauna Kea were offline for a short time after the earthquake, but the larger, more sophisticated telescopes including Keck, Gemini and Subaru are still recovering.

Gemini escaped without any serious problems except for its Secondary Control System (SCS). This is a sophisticated piece of electro-optics that controls the motion of Gemini's high technology secondary mirror. The secondary mirror can perform high-speed tip-tilt motion to correct for windshake and a small amount of atmospheric turbulence. The SCS also performs chopping where the mirror moves quickly back and forth between two points close separated on the sky during mid-infrared observations.

Recent tests of the SCS have demonstrated that the problem detected a few days ago is very likely due to a bad position sensor and/or associated cabling. Unfortunately these components are deeply embedded within the tip/tilt system and Gemini must remove the secondary mirror from the telescope and perform the necessary repair work in the summit lab. Given the time needed to remove the secondary from the telescope, receive new parts, install them, then mount the secondary mirror assembly back on the telescope, Gemini North will be shutdown for at least 2 more weeks. When the secondary mirror is repaired and night-time tests are possible, we still must make a variety of telescope performance tests before going back into science operations.