Study On The Restoration Algorithm Of Distorted Spots In Laser Link Between Satellites

Satellite laser communication technology has outstanding advantages such as high data transmission rates,good confidentiality,small terminal sizes,low power consumption,and has a good application prospect.Therefore,it has become a key research project of scientific research institutions at home and abroad.In the satellite laser communication process,a key step in establishing and maintaining a stable communication link is fast acquiring and stable tracking.The key to success in these two steps lies in the precise positioning of the spot on the detector.In the inter-satellite laser communication links,since the communication distance is very distant,the beam received by the receiving end is approximately parallel light,and an important factor that affects the positioning algorithm is the distortion generated by the optical system.The Cassegrain optical system is affected by the non-uniform temperature change in the space environment,and the thermodynamic deformation occurs.The change of the mirror surface shape will cause the wave-front distortion of the transmission beam,and the energy distribution of the light field received by the detector will be a result of the change,the shape of the spot will change.At this time,the centroid of the spot calculated by the positioning algorithm will produce an error,which will have an adverse effect on the acquiring and tracking process.In this paper,for the inter-satellite laser communication link,since the wave-front distortion caused by the thermal deformation of the optical system generates a positioning error,a restoration algorithm is proposed to correct the centroid of the spot,and recover the distortion spot image in position.Firstly,by analyzing the imaging process,a wave-front distortion model is established based on the Zernike polynomial.Then an objective function is established between the model and the detected image.The conjugate gradient method is used to solve the Zernike polynomial's coefficient.Finally,based on the wave-front distortion model,through the gray-scale centroid localization algorithm,establishes a connection between the centroid positions before and after spot distortion,corrects the position of the centroid of the distorted spot.and finally achieves recovering a wave-front distortion spot.In this paper,MATLAB software is used to recover the distortion of a variety of primary aberration aberrations to restore the effect of the algorithm on the recovery of the spot;This paper uses Zemax software to simulate the thermodynamic deformation of the Cassegrain optical system through face type settings to verify the restoration effect of the recovery algorithm on the distortion spot;And to perform the thermal balance test of the laser communication terminal,using the collected spot tests the effectiveness and reliability of the algorithm.