Telescope Structure
Drives and Controls

General

The telescope structure is a 45 ton steel structure and will be constructed to accuracies of 3mm at critical points. It controls the azimuth position of the telescope and reports this position to the telescope control system (TCS) to an accuracy of 5 arc-seconds. It will be a very stiff structure, with a lowest natural frequency of 7 Hz.

The main purpose of the structure is to:

• Keep a fixed orientation between the tracker and primary mirror at all times, including windy periods in which the open dome shutter points into the wind.
• Accurately rotate the primary mirror and tracker in azimuth and maintain the final azimuth and elevation angles relative to the horizontal.
• Provide an interface for the kinematic mounts of the primary mirror truss.
• Position the primary mirror in azimuth accurately with respect to the alignment (CCAS) tower in order to facilitate the alignment of the primary mirror segments.
• Provide an interface for the tracker rails on which the tracker bridge runs.

The telescope structure is divided into two separate sub-systems, the structure itself and the drives and controls for moving the structure.