Research Of Misalignment Detection Technology Based On Heterodyne Interferometry

With the launch of satellite gravity field detection missions,inter-satellite laser interferometry has received widespread attention in the aerospace field.Compared with microwave detection technology,laser interferometry has a long range,high accuracy and strong anti-interference,and has obvious advantages in the establishment of ultralong-range interplanetary links,and has gradually become an important technical means in deep space exploration and long-range interplanetary communication in recent years.Due to the small diffraction angle of the laser,only when the master and slave spacecraft achieve precise alignment and maintain a stable tracking level,can they accomplish high-precision scientific exploration and communication tasks.Affected by the ultra-long interstellar distance and complex space environment,the detection error of the laser beam misalignment angle will increase,making it more difficult to establish a stable laser link.In this study,the off-target detection technology in interstellar laser outlier interference system is investigated,and the current domestic coherent laser off-target detection technology is analysed and compared,and finally the differential wavefront sensing principle is chosen to design the off-target detection implementation system,which uses the phase information of the photocurrent signal as the off-target detection information,and theoretically has a higher detection resolution than the traditional spot position detection method.The main research elements are.(1)Based on the analysis of the principles of coherent detection and differential wavefront sensing,the experimental system for coherent laser off-target quantity detection is designed,and the system evaluation index and specific scheme design are introduced.(2)A digital phase-locked loop phasemeter based on an adaptive Kalman filter is proposed to address the contradiction in response speed and noise immunity performance of conventional low-pass filters in the design of orthogonal phasemeters.The noise immunity of the phasemeter is effectively improved while ensuring the response speed of the system.When the signal-to-noise ratio is 5d B,the maximum error and root-mean-square error of the phase measurement scheme proposed in this paper are reduced by 80.9% and 64.3% respectively.(3)Based on the comparison of several commonly used goniometric algorithms,a goniometric algorithm based on the improved differential evolution algorithm is proposed,and the mathematical model of off-target detection is directly solved using the differential evolution algorithm,achieving a solution accuracy better than 1nrad.To address the problem that the convergence speed of the standard differential evolutionary algorithm decreases in the late stage of optimization,an improved solution is proposed for the variation factor and crossover factor,which improves the solution speed by 30%.(4)A two-degree-of-freedom laser interference experimental platform is built,and the angular error is less than 5 μrad in the range of 500 μrad,which verifies the rationality of the proposed off-target amount detection scheme.The off-target detection system based on the differential wavefront can basically achieve the off-target detection of coherent light in the laboratory environment,which provides an important reference value for the future research of coherent light precision pointing control technology.