Simulation alignment of optical system for space gravitational wave telescope

Abstract

The performance of telescopes, important components of space interferometry systems, directly affects the accuracy of gravitational wave signals. Space gravitational wave telescopes typically employ an off-axis four-mirror system. When aligned, this system not only has multiple misalignments, but also exhibits interrelated aberrations from various misalignments. These characteristics may lead to difficult alignment of the telescope system as well as significant deviation between the position of the telescope after alignment and the ideal position. To address these issues, first, a sensitivity matrix equation was established between the misalignment of optical components and the Fringe Zernike coefficients. Based on the sensitivity matrix equation, a damping least-squares evaluation function was constructed to reduce the significant deviation between the aligned and ideal positions. Second, a typical optical system of a space gravitational wave telescope was designed, and the sensitivity matrix was calculated. The relationship between the wavefront distortions caused by misalignments in each optical component was examined. To simplify telescope installation, a strategy using secondary mirrors as compensatory elements was proposed. Finally, to verify the effectiveness of the scheme, 200 sets of tolerance files were randomly generated. Based on the evaluation function of the damping least-squares method, a reasonable damping factor was set to limit the solution range of the misalignment, which enabled calculating the secondary mirror compensation amount. Experimental results indicate that after aligning the 200 random telescope files, the root-mean-square wavefront error was reduced to less than 0.0030λ, and the maximum error between the magnification after alignment and the ideal position magnification was only 0.57%, which confirms the feasibility of this alignment scheme.