The optical performance test and analysis of primary and secondary mirrors of a Cassegrain telescope

The optical payload of developing space-borne remote sensing instrument is a Cassegrain telescope with 466 mm clear aperture. The optical surfaces of primary and secondary mirrors of this telescope are both aspherical surface. Whether using CGH or null lens for testing aspherical surface, the technique of alignment is challenging and complex. In this article, the new testing method and analysis algorithm called bench test is presented. The Zernike coefficients of residual manufactured form error and deformation caused by external force and gravity effect will be analyzed by wavefront measurement with rotating primary and secondary mirror individually. According to the analyzed Zernike coefficients from the form error of primary and secondary mirror, the best orientation of secondary mirror refer to primary mirror will be simulated by optical software. As the result, it is an effective way to compensate residual manufactured form error for primary and secondary mirror to gain the best optical performance for the system.