Planar angle metrology: G-LAS, the INRIM - INFN ring laser goniometer

Precision mechanical industry, geodetic measurements, astronomy and experimental physics require accurate measurement of angles down to the nanoradian level. A collaboration between INRIM and INFN is developing a new transportable goniometer (G-LAS, GyroLaser Angular Standard) that makes use of a ring laser gyroscope mounted on a precision turntable with a target accuracy of 10 nrad, being the accuracy of the most precise existing angular encoders at the level of some 100 nrad. The apparatus will consist in a square optical cavity of about 0.5 m in side, equipped with the last generation dielectric super-mirrors that are employed in the large gyroscopes for application in seismology and geodesy.