Imaging Quality Analysis of Navigation and Terrain Cameras for China's First Mars Exploration Tianwen-1 Mission

The Navigation and Terrain Camera of Tianwen-1 Mars Rover is mainly used for the guidance, navigation and control of the Mars rover, and it will also be used for scientific research works.Due to the complexity of the working environment of the Mars rover, its optical imaging system is easily affected by stray light, which forms stray light radiation on the image plane, thus reducing the imaging quality and affecting the accuracy of navigation. In this paper, the variation of irradiance of image plane with incident angle in camera field of view is studied, and the irradiance distribution of each lens surface is compared and analyzed. Combined with the principle of bidirectional reflectance distribution function (BRDF), the reason of irradiance variation law is analyzed. Referring to the results of the irradiance distribution analysis, it can avoid the influence of the stray light in the specific direction on the normal imaging of the camera in the actual detection process. The imaging quality and aberration of the optical system are analyzed and evaluated by combining the spot diagram, MTF curve and Seidel coefficient, and the results meet the needs of practical application. Then the imaging quality change of the optical system in the range of -110 degrees C similar to 60 degrees C are analyzed. Finally, the tolerance of the whole system is analyzed.