High precision laboratory geometric calibration is the basis for the validity of on-orbit data of the Directional Polarimetric Camera. However, the difference in refractive index between the laboratory geometric calibration environment and the on-orbit vacuum environment can lead to changes in instrument geometric performance. The geometric performance difference of the instrument in the standard atmospheric environment and vacuum environment was analyzed by Zemax. The image point position deviation of the instrument in the two environments increases monotonically with the FOV. The image point position in the standard atmospheric environment is further away from the optical axis. When the FOV of the incident beam is 60o , the image points position deviation in all bands is greater than 1.42 pixels. Then, the laboratory carried out the environmental difference verification experiment based on the geometric performance verification light source. The experimental results are in good agreement with the Zemax analysis results, and the average deviation in the 670 nm band is less than 0.01 pixel. Finally, the laboratory geometric model parameters of the Directional Polarimetric Camera are corrected according to the Zemax analysis results. The corrected geometric model parameters will effectively improve the on-orbit geolocation and image registration accuracy of the Directional Polarimetric Camera.
To appraise the photoelectric performance of area CCD for the cloud and aerosol polarization camera (CAPC), a kind of general photoelectric parameter automatic measurement apparatus is proposed. The equipment is produced possessing optical electromechanical integrated structure, which is comprised of the illumination assembly, the CCD imaging assembly and the control assembly. The software of large area CCD parameter automatic test system is designed and achieved. It can realize automatic measuring for the key parameters of a great variety of linear or area CCD, including defective pixels, dark current, relative spectral responsivity, saturation grey value, linearity error, etc. The photoelectric parameters and the spectral response of CCD produced by E2V Company are measured and processed. The research results reveal that the dark current is double when the working temperature of CCD is increased by 6℃. The relative spectral response measurement covers the spectral range from visible to near infrared bands and the spectrum resolution is 1 nm. The automatic measurement program can effectively improve the work efficiency approximately one fold and the overall test time is reduced by about one third. The evaluation of the detector performance provides a guarantee for the performance test and calibration requirements of the whole instrument.
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