Research And Analysis Of GF-4 Cross Radiation Calibration Technology

Gf-4 is China's first remote sensing satellite in geosynchronous orbit,which can observe China and its surrounding areas through pointing control.It is mainly used in forest fires,floods,oceans,agriculture and other fields.Since the launch of GF-4 in 2015,due to the constant changes in the space environment and the degradation of optical performance of the optical sensor,there are certain deviations in the radiation performance of the sensor.At present,the calibration of GF-4 is carried out only once a year,so the real-time monitoring of sensor performance changes and timely update of calibration coefficient cannot be achieved.Under this background,how to realize the dynamic monitoring of GF-4 through the existing technologies and data,improve the accuracy of GF-4 data,and apply the data in more fields and industries has become the main content of this study.The following is the main work completed by this article:1.Based on the analysis of the GF-4 near-infrared spectrum and visible light,the reference sensors selected were MODIS,GF-1 and Land Sat8,and the dunhuang national radiation calibration field was used as the experimental area for cross radiation calibration.By comparing the calibration results of the three reference sensors,it is shown that the calibration error of the reference images based on Land Sat8 image data is about 3%,and that of the reference images based on MODIS and GF-1 image is about 5%.It can be seen that the calibration coefficient of Land Sat8 is closer to the official calibration coefficient and more able to meet the quantitative needs of remote sensing.2.A differential weight fitting method is proposed for the infrared spectrum of GF-4 medium wave.In this thesis the atmospheric infrared sonde(AIRS)as the reference sensor,select eight calibration site for experimental area,with an average weight fitting three bands of fitting,differences in weight and fitting three spectral matching method to solve the calibration,calibration coefficient contrast standard calibration coefficient,calculated results show that the difference in weight fitting calibration coefficient is closer to the official calibration coefficient.In order to further prove the effectiveness of this method,the apparent radiation brightness and brightness temperature values were calculated by these three methods respectively,which were compared with the official apparent radiation brightness and brightness temperature values.The results show that the apparent luminance calculated by the differential weight fitting method is closer to the official calculation value,with an error of less than 10%,while the brightness temperature error is about 1K.The validity and feasibility of the differential weight fitting method are verified by the multi-site method.Therefore,this study provides an effective calibration method for GF-4 single band and multi-band calibration.