M1 Cell
The purpose of the M1 Cell and support system is to support the 4.0m diameter primary mirror and to maintain it’s alignment with the other telescope optics.
M2 Cell
The primary mirror cell assembly consists of the following:
Mirror Cell
The mirror cell which is a steel structure roughly five metres in diameter and 0.6 metres deep. It has a central recess to accommodate the instrument rotator. Apertures allow access to the primary mirror axial supports and ventilation of the primary mirror.
Axial and Lateral Supports and Definers
The mirror is supported on a bed of 81 axial supports and 24 lateral supports which gradually support the weight of the mirror as the telescope moves towards horizon pointing.
The support system also corrects the shape of the mirror as it distorts due to gravity and other external forces by modifying the support forces applied to the mirror by the axial supports.
Axial location of the mirror on the cell is provided by 3 ‘rigid’ defining axial supports while lateral position is provided by 3 tangential struts.
The axial supports consist of frictionless pneumatic cylinders with rolling element seals mounted into the mirror cell through precision machined holes. The lateral supports consist of struts attached to the M1 Mirror using a glued interface pad of Invar, low friction ball bearings and a sealed pneumatic cylinder. The following figure shows one of the two types of lateral support
Passive Earthquake Restraint & Maintenance Restraint
A set of passive restraints are provided to ensure that during an earthquake event the primary mirror cannot be propelled beyond the safety of the mirror support system. In addition a set of maintenance restraints are also provided so that when the pneumatic support system is turned off, the primary mirror is held securely in place within the cell.