Pose Adjustment Capability of Secondary Mirror in Correcting Gravity Deformation of Large Aperture Remote Sensor

Abstract

For large aperture remote sensor, it is a difficult task to ensure the ultrahigh pose accuracy of mirrors. To solve the problem, this paper attempts to correct the pose misalignment induced by the gravity deformation through pose adjustment of the secondary mirror. Firstly, an ultra-lightweight remote sensor (diameter: 2.4m) was designed, and a finite element model (FEM) was constructed to analyze the influence of gravity deformation on the sensor. The analysis shows that the gravity deformation of the primary mirror and the secondary mirror exceeded the tolerance limits. Hence, a pose adjustment design was proposed for the secondary mirror to correct the misalignment of the optical system. To verify its correction effect, the pose adjustment plan was applied to correct the misalignments of the optical system caused by gravity deformation. The results show that the pose adjustment plan eliminated the effect of gravity on the ground, and corrected the misalignments after the sensor is in orbit. Overall, the proposed design greatly reduces the fabrication difficulty of the large aperture remote sensor, and effectively improves the sensor's imaging quality in orbit.

Low Spatio-Temporal Frequency Wavefront Aberration Correction Method Based on a Movable Secondary Mirror

“…THE DYNAMIC ABERRATION CORRECTION BASED ON HEXAPOD To achieve dynamic correction for low spatio-temporal frequency aberrations, secondary mirror demands for a dynamic platform that can adjust at higher frequencies in five degrees of freedom. Hexapod platform has been widely used as a secondary mirror adjustment platform for large photoelectric telescopes for advantages such as precision control, structural rigidity, high load capacity, system stability, and no position accumulation errors, etc [20]. The Hexapod of POST Solar telescope comes with a highest adjustment frequency of 0.5Hz, which is taken as the frequency of aberration correction.…”