Study On Imaging Quality Of Airborne Hyper-spectral Imager

Hyper-spectral remote sensing is a kind of detection technology, which developed on the basis of multi-spectral remote sensing technology. It has good characteristics like high spectral resolution, multi-spectral band number, informative, significantly improved the ability to detect the earth’s surface features and objects in nature. It has been widely used in mineral resources investigation and uncover of military camouflage or other aspects. Hyper-spectral imager application is based on quantitative data. Not only need to get a clear image, but also requires the remote sensing data have sufficiently spectral stability. So studying on hyper-spectral Imager imaging quality has important engineering significance for development and applications of hyper-spectral imager.In this paper, for the airborne hyper-spectral imager which applied in mineral exploration, the author developed a engineering prototype, analyzed how the airborne imaging environment(mainly temperature and posture) changes effects imager’s imaging quality, and studied the imaging properties and spectral stability. Based on the theoretical analysis, the author carried out hyper-spectral imager imaging test flight, using the engineering prototype. And the obtained remote sensing images were analyzed and evaluated, which verified the imaging properties and the spectral stability of instrument.Firstly, the author carried out the development of engineering prototype of the hyper-spectral imager. According to the technical requirements, the author proposed a scheme of modular design, used the L-shaped base plate integrating design solutions. The engineering finite element analysis was performed using MSC.Patran & MSC.Nastran software. The results showed that the instrument had good stiffness characteristics and surface accuracy. The baseband reached 297.8 Hz, and the RMS value of the primary mirror is only 4.6 nm. Finally, the author completed the works of machining, assembling, adjusting, detecting and calibration of airborne hyper-spectral imager’s engineering prototype.Then, on the basis of the above work, the author got on in-depth theoretical analysis for airborne imaging environment typical factors(ambient temperature, the carrier aircraft attitude changes) influencing on the hyper-spectral imager imaging quality, and carried out the study of the imager imaging characteristics and spectral Stability. Firstly, the author studied how the temperature affect on the hyper-spectral imager’s imaging quality. According to the thermal design and related test data of airborne hyperspectral imager, analyzed the characteristics of the actual temperature loads under airborne environment; Prepared the rigid displacement and surface error solver as the theoretical basis of least squares fitting and homogeneous coordinate transformation method; Conducted the optical ray tracing to deformation system, and studied its spectral drift characteristics and affects to the system transfer function. The results showed that, within ±10 temperature range, the spectral is stable, no further ℃need of spectral calibration and spectral correction. Then, the author analyzed the impact of the attitude to the hyper-spectral imager imaging quality. The author Established a precise image motion velocity vector computation model using the homogeneous coordinate transformation method; Proposed the requirements of attitude accuracy which will guarantee the imaging quality; Determined the compensation accuracy of stable platform; Analyzed the impact of compensation error of platform attitude to image motion rate; Studied the distribution of flight parameters indicators with a given imaging quality requirements, and analyzed image motion velocity errors. The results showed that the stable platform can effectively compensate posture to meet the requirements of imaging quality.Finally, a hyper-spectral imager indoor imaging tests and small areas of aviation flight imaging tests were carried out. The system transfer function was measured by the blade edge method using the obtained image data, and performed imaging quality evaluation; Extracting the spectral curve of feature from image data, verified its spectral stability by the offset of oxygen absorption. The results showed that airborne hyper-spectral imager has a good imaging quality and spectral stability.Subsequently, This airborne hyper-spectral imager can be further improved. Improving the accuracy of the instrument target identification and classification of surface features, it can take some geological remote sensing missions.