位于南北极的Dome C和Greenland冰雪目标是国际上应用比较广泛的定标跟踪目标。但由于极昼极夜现象的存在,单一极地冰雪目标难以对遥感仪器连续定标跟踪。针对这一不足,提出联合使用两个极地冰雪目标对风云-3A卫星(FY-3A)/中分辨率光谱成像仪(MERSI)太阳反射率波段辐射性能进行连续跟踪监测的方法。首先,利用FY-3A/MERSI寿命晚期相对稳定的观测数据,建立两个冰雪目标表观反射率的双向分布函数模型;然后利用该模型,对冰雪目标的表观反射率序列进行归一化,消除由冰雪目标非朗伯性引起的变化信息,获得反映遥感器辐射性能变化的参量,实现不同冰雪目标数据序列的融合;最后,采用二次多项式拟合模型,对融合后的数据进行变化趋势分析,并与其他相关研究成果进行比对验证。结果发现,跟踪监测模型的不确定性基本优于3%,特别是在波长小于550 nm的短波段,不确定性优于2%。衰减率结果显示,蓝光波段衰减显著,特别是波段8(413 nm),年均衰减率接近7%;红光和近红外波段(水汽通道除外)最为稳定,年均衰减率在±0.5%以内。验证结果显示,所提方法与其他方法具有很好的一致性,大部分波段的多年总衰减率偏差低于3%。

Snow targets of Dome C and Greenland in the south and north poles are the calibration tracking targets, which are internationally applied. However, due to the existence of polar night phenomenon, it is difficult to continuously calibrate and track remote sensing instruments in a single polar ice and snow target. In response to this problem, a method of continuous tracking and monitoring of the radiation performance of the FY-3A/medium resolution spectral imager (MERSI) solar reflectance band using a combination of two polar ice targets is proposed. Firstly, using the relatively stable observation data of FY-3A/MERSI in late life stage, two bidirectional distribution function models of apparent reflectivity of ice and snow target are established. Then, the model is used to normalize the apparent reflectivity sequence of ice and snow target, eliminate the change information caused by the target non-Lambertian, obtain the parameters that reflect the change of the radiation performance of the remote sensor, and achieve the fusion of different ice and snow target data series. Finally, using the quadratic polynomial fitting model, the trend of the data after the fusion is analyzed, and it is compared with other related research results. The results show that the uncertainty of the tracking model is better than 3%, especially for the short wavelength of less than 550 nm, in which the uncertainty is better than 2%. Attenuation rate results show that the blue band attenuation is significant, especially in the band 8 (413 nm), the annual average attenuation rate is close to 7%. The red and the near infrared band (excluding the water vapor channel) are the most stable wave bands, and the annual average attenuation rate is within ±0.5%. The verification results show that the proposed method is in good agreement with other methods, and the deviation of the total attenuation rate of many years in most bands is less than 3%.