Sensitivity analysis of a wide-field telescope

Abstract

We are developing three ground-based wide-field telescopes. A wide-field Cassegrain telescope consists of two hyperbolic mirrors, aberration correctors and a field flattener for a 2-degree field of view. The diameters of the primary mirror and the secondary mirror are 500 mm and 200 mm, respectively. Corrective optics combined with four lenses, a filter and a window are also considered. For the imaging detection device, we use a charge coupled device (CCD) which has a 4096 × 4096 array with a 9-µm² pixel size. One of the requirements is that the image motion limit of the opto-mechanical structure be less than 1 pixel size of the CCD on the image plane. To meet this requirement, we carried out an optical design evaluation and a misalignment analysis. Line-of-sight sensitivity equations are obtained from the rigid-body rotation in three directions and the rigid-body translation in three directions. These equations express the image motions at the image plane in terms of the independent motions of the optical components. We conducted a response simulation to evaluate the finite element method models under static load conditions, and the result is represented by the static response function. We show that the wide-field telescope system is stiff and stable enough to be supported and operated during its operating time.