Research On Segmented Mirrors Detection Technology Of Earth Observation Synthetic Aperture System

With the demand for the field of earth observation,the development of highresolution space telescope has become an inevitable trend.However,the high resolution of the telescope system will inevitably lead to the further increase of the aperture of the optical system.Mainly focus on the demand of the future very high resolution infrared on-orbit observation large-caliber segmented telescope system,a scheme of segmented primary mirror formed by fan-shaped sub-module is carried out,which would be folded up for launch and spreaded in the orbit.For the detection of the segmented primary mirror system,it proposes to use star-light as the detection light source to help to detect the segmented primary mirror on-orbit,and a self collimation scheme is carried out to a real time monitoring of the segmented primary mirror.An experimental verification system has been established and preliminary experimental verification has been carried out.The work of the thesis has important reference value for the application of synthetic aperture technology in future high-resolution on-orbit earth observation systems.The main contents of this paper are as follows.Firstly,according to the spatial resolution requirements of the future very high resolution Earth observation system,analysis of optical aperture has been carried out,for the Earth observation system with a tracking height of several hundred kilometers,the resolution of the optical systems with a diameter of several meters in size are sufficient enough to meet the requirements of visible and infrared Earth observation systems.For the Earth observation system with moderate aperture,the article analyzes and compares the different forms of sub-mirrors structures,and proposes a fan-shaped segmented primary mirror,which is segmented by several sub-mirrors and folded around a central fixed mirror,and is more suitable for space applications.A scheme of the on-orbit operation and debugging process is carried out with the star light source inspection technology and self-collimation detection technology as the core technology.The article establishes the relationship between the wavefront aberrations of the system and the off set errors of the fan-shaped mirrors,and analyzes the sensitivity of different off set error terms to the wavefront aberration of segmented system.According to the independent off set errors,the aberration control and adjustment optical model are established,which provides a theoretical basis for the detection and control of each segmented fan sub-mirror.Secondly,according to the segmented primary mirror,a co-foucus error detection system based on the traditional Shack-Hartmann wavefront sensing technology and a co-phase error detection system based on the circular aperture Fraunhofer diffraction theory are established.Because of the vibration of the experimental platform,environmental disturbances,and the micro drift of the satellite platform attitudes in future application,the centroid of mass of the Shack-Hartmann spots array makes irregular jitter,which leads to the co-focus error detection system cannot meet the high-accuracy requirement.In order to solve this problem,a method of continuous frame rate image sampling and processing is proposed to overcome the influence of environment.It effectively improves the signal-to-noise ratio of spot centroid extraction and the detection accuracy of the confocus error detection system.According to the characteristics of the sub-mirrors,a circular aperture mask and a microprism array are designed for the co-phase error detection system.In the mean time,a phase difference plate has been used in experiment to take a simulation test,the testing results verified that the detection accuracy of the co-phase error detection system is well maintained in the range of 1/20 wavelengths.At last,aming at the earth observation synthetic aperture system,a method for realtime monitoring of segmented primary mirror by optical self-collimation is proposed.A compound cube-corner prism is designed,and a self-collimated co-focus detection system is constructed to monitor the quality of the segmented primary mirror.By the simulation and experiment,the feasibility of the scheme is verified?...