Characterisation of the C-II Ring Laser

Abstract

The precise measurement of Earth Rotation in Geodesy is not yet possible with inertial sensors since their resolution, and more importantly their stability, is still insufficient. Mechanical gyros and fibre optic gyros are widely used in aircraft navigation and robotic systems. However the requirements for stability and resolution are far below of those in the geosciences. The successful construction of the Canterbury Ring Laser (C-I) has demonstrated that it is possible to build and operate large ring laser gyroscopes. An instrument (G = Grossring) with an area of 16 m2 and with two counterrotating laser beams following its circumference has the potential to provide Earth rotation measurements with a stability of 10-9 or better [3,4] . Based on experience with a simple (C-I) ring laser a monolithic prototype (C-II) of such a large ring laser was designed and built in order to investigate the properties of a very large ring laser. The concept, and the results obtained so far, are discussed.