A piecewise deformable subreflector for compensation of Cassegrain main reflector errors

The subreflector presented is built of an aggregate of rigid panels, which are controlled by a small number of actuators. An algorithm is described to calculate the actuator motions for a set of given surface distortions. It is assumed that the surface distortions, at different elevation angles, are known a priori. Geometrical optics is used to describe the aperture field distribution and to predict the improvement in performance. Computer modeling of main and subreflectors was used to test the design. This design is suggested for the improvement of a hypothetical radio telescope. In this example, it is predicted that the effective surface errors, due to gravitational distortions, may be reduced to 33% of their uncorrected level with a 48-plate subreflector. Compensation with other subreflector configurations is also investigated