Images of outdoor scenes usually have low contrast and degraded visibility in snowy weather. Snowflakes, deemed as particles in the atmosphere, cause light scattering and absorption, blurring the images. Polarization-based scenarios are proven effective in restoring the images. However, current methods either inaccurately estimate atmospheric airlight at infinity or have low efficiency. To enhance the accuracy and efficiency for increasing visibility and correcting the color shift, we propose a simple method based on polarimetric images. This method uses the maximum value of the degree of polarization and angle of polarization by global analysis of the Stokes vector to accurately estimate atmospheric airlight at infinity and the transmission map. Experimental results confirm that this method can significantly improve the image quality without complex model implementation or any other processing and has high computational efficiency. Moreover, the comparison results demonstrate that this method can recover more details and depth information.

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Spaceborne CO2 imaging spectrometer is a high spatial resolution, high time resolution, non-contact and long-term monitoring, which is widely applied in the field of monitoring the change of global greenhouse gas. For achieving long-slit, high signal to noise ratio and high spectral image quality, the principle of initial structure of Offner convex grating imaging spectrometer was analyzed by utilizing the central wavelength of tangent of meridian and sagittal rays at slit, enhancing the utilization rate of incident light and avoid vignetting effectively. Based on this scheme, the optical system of Offner convex grating imaging spectrometer was designed. The imaging spectrometer with 35 mm slit, that the swath can achieve 233 km. For enhancing inversing CO2 gas concentration efficiency and accurately, the spectrometer designed working spectral range at 1590~1620 nm. In addition, in order to achieve 0.1 km spatial resolution at 500 km orbit, the front telescope optical system was designed. The FOV of the front telecentric telescope optical system is 13.14°, focal length is 75 mm. Finally, analyzing the overall optical system that includes telescope and convex grating imaging spectrometer. The design results show that the root mean square (RMS) radius of the sequence diagram is less than 5 μm, and the modulation transfer function of the system at 33 l p/mm is better than 0.7. The design scheme satisfies remote sensing detection requirements of large field of view, high spectral resolution and high signal-to-noise ratio for spaceborne CO2 imaging spectrometer.

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