Research On Mid - Short Wave Infrared Radial Scaling Method Based On Stellar Observation

Before the remote sensor is sent into space, it is necessary to accurately measure the radiometric calibration coefficient of the sensor in the laboratory, as laboratory radiometric calibration or pre launch radiometric calibration. In space, radiation calibration coefficient changes, due to the violent vibration during flight, surrounding environment of the sensor changes. After the sensor is in orbit, on-orbit radiometric calibration is required to correct the radiometric calibration coefficient. Absolute on-orbit radiometric calibration could evaluate the radiation response characteristics of the sensor in real time, discover and rectify the change of the radiation response, and improve the quality and utilization of the satellite data. In the visible and short infrared wave, sun is often used as the radiometric calibration source; In the long infrared and microwave wave, black body is often used as the radiomet ric calibration source. For the medium and short infrared wave, star-observation is more appropriate to be used as a radiometric calibration source. In this paper, use the stable star as the radiometric calibration source for the band between 2.5μm and 5μm.Star relative to the semi-field of a detection system is far less than the instantaneous field of view（IFOV）, star can be considered as a point target. Need to precisely estimate the position of the point targets relative to the detection’s IFOV; There are significant differences between the actual point source distribution and the image received by the sensor due to the influence of Point spread function（PSF）. To restore the real situation of the point source, sensor’s PSF is required ahead of time. Also need to estimate the star radiant energy between 2.5μm and 5μm band.In this paper, use the Gauss’ s function model to simulate the sensor ’s PSF in two-dimensional. Estimate the position of the point targets relative to the instantaneous field of view by using the minimum two multiplications method; estimate the weight distribution of the sensor’s PSF in sub pixel scale with the specific observation method,the accuracy is high to be 0.01% in this model, provides the linear contribution to the accuracy of absolute radiometric calibration; use the WISE star-observation in band between 3.4μm and 4.6μm, estimate the star radiant energy in 4.3μm band,the accuracy of the star energy estimated results is within 1%; results show that if the calibration accuracy is within 5%, the accuracy of estimating the position needs to be within 2%, when the center point energy of the Point spread patch is lower than 64%(MTF_0.5 <0.25) of the total diffuse patch, the accuracy meets the requirement. In summary, when the transform function(MTF_0.5) of the detection system is lower than 0.25, star-observation calibration accuracy meets the requirement of 5%.