Research On Infrared Cloud Imaging System For Satellite-earth Laser Communication

With the rapid growth of data volume of space communication between the Earth and the stars,the development of transmission rate of traditional microwave link can hardly meet the future development demand of the backbone network of the Earth and the stars adequately.In this case,space laser communication becomes one of the options to solve the bottleneck of satellite-terrestrial communication by virtue of its high transmission rate,large available bandwidth,strong anti-electromagnetic interference capability and good confidentiality.However,the atmospheric transmission reliability of satellite-terrestrial laser communication is poor,and clouds,fog and rain can affect the link,the most critical of which is the absorption of clouds.Therefore,long-term measurement and monitoring statistics of the cloud data over the available ground stations are needed.The research content and contributions of this paper are divided into the following three aspects.First,for the interference of clouds in satellite-ground laser communication,this paper designs and implements an infrared cloud imaging system for long-term measurement and analysis of cloud coverage over ground stations.Based on the cloud radiation characteristics,the cloud layer is detected and classified in combination with the atmospheric radiation transmission software MODTRAN4,and the optical depth of the cloud is obtained to indicate the attenuation degree of the cloud layer to the laser,and the height of the cloud bottom is inverted.Then to further improve the cloud image accuracy,this paper proposes an algorithm to compensate for the temperature drift of the focal plane array,and corrects the output response of the uncooled infrared camera with the external temperature change by modeling and analyzing the infrared camera.The algorithm can improve the output image accuracy of uncooled infrared cameras in the external environment.Finally,this paper addresses the problem of insufficient field of view of single camera imaging by stitching multiple cameras to achieve full-sky cloud images on the basis of ensuring high spatial and temporal resolution.In summary,this paper designs an infrared cloud imager system for real-time acquisition of cloud data over the ground station site day and night with high temporal and spatial resolution,and further radiometric calibration and data processing of cloud infrared images to obtain the optical depth,cloud height and other characteristics of clouds,so as to provide reliable services for the establishment of an effective satelliteground laser communication link.Through the above work,the infrared cloud imager system designed in this paper can provide reliable services for satellite-terrestrial laser communication.