风云三号D星(FY-3D)于2017年11月15日成功发射, 是我国第二代极轨气象卫星, 其上搭载了红外高光谱大气探测仪(HIRAS), 实现了地气系统的高光谱分辨率红外高精度观测, 由于光谱频率的精确性会直接影响辐射精度, 红外干涉仪器必须进行逐通道的光谱定标。首先对干涉图数据进行傅里叶变换获得粗定标结果, 再基于仪器参数计算仪器线型函数, 进行光谱精校正, 开发了风云三号D星HIRAS的光谱定标技术, 并用发射前和在轨数据进行了精度验证。光谱定标方法能有效订正由于仪器离轴探元设计引起的光谱位置偏差, 基于地面单色激光测量数据验证, 长波4个探元20×10-6左右的偏差可订正到0.5×10-6(1和2探元)和7×10-6(3和4探元)以内; 中波1四个探元50×10-6左右的偏差可分别订正到6×10-6(1和3探元)、8×10-6(2探元)和13×10-6(4探元)以内; 基于在轨数据验证三个波段光谱订正后光谱精度偏差和标准差均可达到5×10-6以内。三个波段光谱定标结果均满足卫星使用技术指标10×10-6的要求, 有效保证了辐射精度评估和后端遥感产品开发应用的要求。

The Fengyun 3D satellite is a second-generation polar orbit meteorological satellite that was launched by China on November 15th, 2017, with a novel High-Spectral Resolution Infrared Atmospheric Sounder (HIRAS), aiming to provide hyperspectral infrared observations. The infrared high-spectral sounder needs to perform spectral calibration for each channel owing to the direct influence of spectral frequency accuracy on radiometric calibration results. First, a rough spectral calibration result was obtained by performing a fast Fourier transform, following which spectral fine correction was applied based on parameters and the Instrument Line Shape (ILS). The spectral calibration technique for FY-3D HIRAS was developed and validated using pre-launch ground test data as well as on-orbit data. The spectral calibration method can correct the frequency offset due to the off-axis detector design, and the spectral calibration bias can reach 0.5×10-6 (detector 1 and 2) and 7×10-6 (detectors 3 and 4) in the long-wave band from a bias of 20×10-6 without ILS correction. For the middle-wave band, it can reach 6×10-6 (detectors 1 and 3), 8×10-6 (detector 2), and 13×10-6 (detector 4) from a bias of 50×10-6 without ILS correction, based on the laser monochromatic measurements of pre-launch test data. The mean and standard deviation of the spectral calibration bias are in the range of 5×10-6 for all the three bands and four detectors based on on-orbit data. The spectral calibration accuracy of all three bands can satisfy the application requirements of 10×10-6; this study provides further insights into the evaluation of radiometric calibration accuracy and product development.