Cassegrain Rotator
The Cassegrain Rotator allows the apparent sky image to stay fixed (non-rotating) on the optical sensors as the Altitude and the Azimuth Axes move to keep the science object in the centre of the telescope field of view.
This is achieved using a combination of a rotational drive system, a slewing ring bearing, multiple read-head encoders and brakes. The bearing which is the heart of the rotator is configured as a precision four point contact bearing.
The instrument is mounted onto the rotator using a set of tapped holes on the rotating part. The precise alignment of the instrument to the rotator is achieved using a set of dedicated alignment features which provide for both adjustment and also high repeatability for removal and replacement of the instrument.
Both the drives and encoder positioning equipment are mounted on the rotator body corresponding parts on the outer and inner sections. The rotator is then attached to the M1 cell structure and aligned.
The cable wrap is a rolling loop type cable wrap, capable of providing mechanical services to the instrument through a rotational range of 540 degrees. The cable wrap is independently driven and its angular position slaved to the rotator.