Research On Radiometric Calibration For Large-aperture Space Optical Remote Sensor

With the development of remote sensing application of in-depth, quantitative remote sensing, automation and real-time network is the trend, and the quantitative is a prerequisite for automation and real-time. Quantitative remote sensing involves the payload performance and image quality, the precision of calibration, error analysis, remote sensing data processing, information extraction, quantitative retrieval and many other links, the most fundamental and the most important step is the calibration. The premise of quantitative remote sensing is that the satellite payload can provide quantitative data and information, so the calibration is necessary and important part of satellite application.Optical payload develops towards the direction of high resolution, large field of view, large aperture and long focal distance. From the remote sensing camera development plan in the future,the remote sensors will step towards large aperture and long focal length in order to improve the ground pixel resolution. With the continuous increase of remote sensor aperture and field of view, we need the corresponding calibration light source to meet the demand of the calibration test.Integrating sphere light source is anideal uniform light device which has good surface emitting uniformity, Lambert characteristic, so far is still commonly used as the calibration source and the testing source at home and abroad. Large aperture integrating sphere light source can provide different levels of radiance and fill aperture and field of view of remote sensors, which can provide end to end absolute and relative radiometric calibration for the sensors.With the continuous increase of space optical payload aperture,the diameter and opening size of conventional integral sphere calibration source need to increase to meet full aperture, full field of view, end to end requirements between the integrating sphere source and optical payload, to achieve all-optical way, full aperture and full field calibration requirements. Therefore the research on the calibration of large aperture optical payload has far-reaching theoretical and practical significance.The quantity of total radiation in the entrance pupil of the on-orbit sensor is determined by space optical radiation transmission model, The establishment of space camera radiative transfer model will transfer the amount of radiation in the entrance pupil into the image DN value,and then deduces the mathematical model for radiometric calibration.Routine laboratory radiometric calibration method is analyzed.According to the structure and characteristics of large aperture space camera, pointing out defects and shortcomings that the radiometric calibration method can not meet the full aperture calibration,the improvement scheme and innovative solutions are proposed in the foundation, meanwhile the feasibility of the scheme is analyzed.Aiming at the improvement of laboratory calibration scheme, a new type of large aperture integral sphere calibration source is established.Five key components of the large aperture uniform radiation calibration source in the development of the system are discussed in detail: automatic matching of radiance level; the light source design; structure design of large diameter uniformity radiation calibration source; main control system design of the large aperture uniform radiation calibration; design of multi probe and line structure radiation performance test system. The uncertainty of the eventually established Integrating calibration source is less than 3.6%, uniformity and cosine characteristics are better than the design requirements.In order to meet laboratory radiometric calibration requirements for continually rising optical aperture of optical remote sensors, a calibration source of high luminance with integratingsphere was designed based on Jones method.The heat dissipation method of water cooling for the calibration light source heat dissipation is designed, the noise through radiation calibration is reduced,meanwhile the radiometric calibration accuracy influence of the air agitation from air cooling is avoided.Finally, radiometric calibrationerror sourcesare theoretical analyzed, combined with the spectrum of non matching, radiation characteristics of the calibration source,the mechanism of the radiation calibration accuracy of space optical remote sensors is described in detail, and also the relative radiometric calibration and absolute radiometric calibration accuracy are analyzed.