FY-3A气象卫星上搭载的紫外臭氧总量探测仪(TOU)是我国首台自主研制的用于日常全球臭氧总量监测的仪器, 自2008年5月发射至2015年3月已成功在轨运行近7年。前期研究表明FY-3A/TOU 仪器辐射响应存在分段差异特征［辐射值大于和小于6.6 μW/(cm2·nm·sr)的仪器响应明显不同］, 存在双线性响应问题。提出了基于欧洲Metop-B卫星上全球臭氧监测实验2(GOME-2)的探测数据开展紫外波段在轨交叉定标研究方法, 进行FY-3A/TOU L1B数据的在轨交叉定标检验, 用于仪器探测值在轨实时比较和校正。2013年2月—2015年2月两年定标结果表明, 2013年8月以前的辐射值比对斜率均为1左右, 表明TOU的探测值在2013年8月以前比较准确, 随后TOU与GOME-2的比对斜率开始偏大, TOU探测值相对偏高, 表明FY-3A/TOU仪器的探测响应发生变化。虽然比对斜率有变化, 但两者的探测辐射值一直保持较好的线性相关性(R2＞0.96), 因此可以通过交叉定标对TOU后期的探测数据进行校正。

Ultraviolet total ozone unit (TOU) is one of the main payloads on FY-3A meteorological satellite and the first instrument for daily global coverage of total ozone monitoring is independently designed and manufactured by China. It has been in-orbit for almost seven years from May 2008 to March 2015. The preliminary study shows that the radiation response FY-3A/TOU instrument is different for different spectrum bands ［the response of the instrument with radiance larger than 6.6 μW/(cm2·nm·sr) is obviously different from the instrument with radiance less than 6.6 μW/(cm2·nm·sr)］. It has the problem of bilinear response. A method is introduced for ultraviolet band in-orbit cross-calibration based on the data detected by global ozone monitoring experiment 2 (GOME-2) on European Metop-B satellite. The data of FY-3A/TOU L1B are checked by in-orbit cross-calibration, and then the rea-time comparisons and corrections of instruments′ detection values are made. The calibration results chosen from February 2013 to February 2015 indicate that the comparison slopes of radiation are all very close to 1 before August 2013, which mean that the detected radiance of TOU is fairly accurate. However, the slopes become a little larger after August 2013, the detected radiance of TOU is relatively larger than GOME-2, which means that the detected response FY-3A/TOU is changed. Although the equation slopes are variant, the relation coefficient between TOU and GOME-2 keeps better linear dependence (R2＞0.96). It means that the later measurements of TOU can be corrected by use of cross-calibration equation.