The Zerodur rods provide thermally stable support for both coarse and fine position sensors for the secondary mirror. After the break, both sets of sensors were loose and able to move freely. The fine sensor (micro-e) is comprised of a scanner and glass grating. The scanner damaged this grating. A replacement scanner/grating pair was installed after the rod was repaired.
After four weeks of recovery efforts from the 6.7 magnitude earthquake that shook the island of Hawai’i on October 15th, the Gemini North telescope resumed regular science operations on November 11 with deep GMOS spectroscopy as part of a queue-scheduled program.
Gemini Director, Doug Simons said, “After four long weeks, the longest shutdown in Gemini’s young history and the first of its kind in the entire history of astronomy on Mauna Kea, science operations have resumed at Gemini North. Needless to say, I am immensely proud of our team.”
The primary earthquake related damage to the Gemini North telescope was a broken rod made of a low-expansion ceramic called Zerodur in the secondary mirror system mounted at the top end of the telescope. The rod (see Figure 1) is about 24 cm long and 25mm in diameter and broke cleanly so engineers were able to successfully adhere it back together with epoxy. The rod is one of three used in the secondary mirror assembly. In addition, a new precision position sensor was installed in the system to replace a sensor damaged by the earthquake.
For more details on the process of Gemini’s recovery from the earthquake see: http://gemini.edu/index.php?option=content&task=view&id=214
