Spectral variability is one of the most limiting factors in hyperspectral unmixing, so it is important to further study the characteristics of spectral variability to improve the accuracy of unmixing. After conducting simulations under varying irradiation conditions, a linear mixed model combining endmember and band is proposed by introducing a band scaling factor to the endmember scaled spectrum. The total variation constraint is used to smooth the spatial distribution of both endmember and band scaling factors and then alternating iterative optimization is applied to solve the optimization problem. Experiments conducted with both simulated and real hyperspectral data sets indicate that the proposed algorithm is effective in hyperspectral unmixing and is superior to other state-of-the-art algorithms based on spectral variability.
Linear mixing model is widely used in hyperspectral images unmixing for its simplicity while the real ground distribution does not satisfy the model. To achieve a high unmixing performance, the nonlinear spectral mixing model should be further discussed. This paper extends the spectral library by adding virtual endmembers based on the second scattering between endmembers to the original spectral library and transforms the nonlinear problem into a linear issue. By introducing the l1 - l2 sparse constraint and enhancing the virtual abundance weight, the optimization problem is solved by alternating direction method of multipliers. Experiments conducted with simulated data sets and real hyperspectral data show that the proposed algorithm is superior to other state-of-the-art methods.
The space-borne HgCdTe infrared detector is widely used in missile warning and interception because of its ability to detect the active tail flame of the missile. The performance of the infrared detector on satellite directly affects the missile's identification and threat assessment. In order to study the effect of temperature on the performance of satellite infrared detector, Noise-Equivalent Temperature Difference(NETD) of the HgCdTe detector is used as the performance reference, and the SBIRS near-earth orbit small satellite's cosmic environment is the analysis background. Radiant energy of the target is analyzed with distance changes. The performance of HgCdTe detector with temperature and distance changes was simulated by mathematics software MATLAB. Which is been used to simulate the change of Noise-Equivalent Temperature Difference due to the increased operating temperature and distance change of HgCdTe infrared detector. which provided calculations reference for the performance analysis of HgCdTe detectors on the satellite.
Based on the heat conduction theory, a theoretical model of HgCdTe detector irradiated by 10.6μm CW laser is constructed. The thermal effect of the detector is analyzed by finite element method when the laser spot velocity is 0m/s, 4mm/s and 10mm/s respectively with the peak power density of 50KW/cm2 . The results show that, the temperature of irradiation point rises rapidly when v=0 mm/s, but the rising speed will be slower and slower and finally reaches the equilibrium temperature under the combined effect of laser irradiation and heat conduction. In the case of relative motion, the position of the peak temperature gradually shifts along the velocity direction. The peak temperature gradually decreases with the increase of the moving speed, and the width of the temperature peak gradually widens with the increasing speed. Relative motion should be considered when studying laser radiation and laser protection.