In-Orbit Calibration of FengYun-3C Microwave Radiation Imager: Characterization of Backlobe Intrusion for the Hot-Load Reflector
In-Orbit Calibration of FengYun-3C Microwave Radiation Imager: Characterization of Backlobe Intrusion for the Hot-Load Reflector
复制标题
风云三号C微波辐射成像仪在轨定标：热负载反射器后瓣侵入表征
DOI：
10.1109/jstars.2021.3075969
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发表时间：
2021
影响因子：
5.5
通讯作者：
Xue Li
中科院分区：
文献类型：
--
作者：
Xinxin Xie;Wanting Meng;Kesong Dong;Songyan Gu;Xue Li
针对风云三号C气象卫星微波辐射成像仪（MWRI）热负荷反射面后瓣干扰问题，提出了一种修正算法。在MWRI的辐射增益的不连续性，由于不准确的后瓣溢出的热负荷反射器，已被诊断。建立了一种将两个不同后瓣场景的辐射增益差与热负荷反射面溢出相联系的物理校正方法，用于估计MWRI热负荷反射面的在轨溢出因子。同时，发现1° × 1°网格的亮温（TB）不能很好地反映后瓣模式，导致辐射增益在海岸线附近发生突变。为了更好地表示后瓣溢出，有效后瓣TB现在是从先进的微波扫描辐射计观测TB的4° × 4°区域上平均的，现在分辨率为0.25° × 0.25°。随着热负荷反射器的调整溢出，辐射增益的异常行为得到有效缓解，在海岸线的改善是显着的，诱导TB变化高达2 K的幅度在10.65 GHz的通道。虽然在这项研究中提出的算法仅限于信道频率高达23.8 GHz，由于其精度的限制，它可以解决类似的问题，这些微波辐射计不能在轨后瓣机动和接收辐射不可避免地从外边缘的热负荷或冷天空反射器。
This study presents a correction algorithm to remove the backlobe intrusion from the hot-load reflector of microwave radiation imager (MWRI) on-board China FengYun-3C (FY-3C) meteorological satellite. Discontinuities in the radiometric gain of MWRI, due to inaccurate backlobe spillover of the hot-load reflector, have been diagnosed. A physical correction method, relating the radiometric gain difference between two distinct backlobe scenes to the spillover of the hot-load reflector, is thus established to estimate the in-orbit spillover factor of the MWRI hot-load reflector. Meanwhile, it is found that brightness temperature (TB) at each 1° × 1° grid could not address the backlobe pattern appropriately, leading to abrupt changes in the radiometric gain occurring near the coastlines. To better represent the backlobe spillover, the effective backlobe TB is now averaged over a 4° × 4° area from advanced microwave scanning radiometer-observed TBs, which is now in a finer resolution of 0.25° × 0.25°. With the adjusted spillover for the hot-load reflector, anomalous behaviors of the radiometric gain are mitigated effectively and the improvement at the coastlines is pronounced, inducing TB variation up to 2 K in magnitude at the 10.65 GHz channel. Although the algorithm presented in this study is only restricted to channel frequencies up to 23.8 GHz due to its accuracy limitation, it could tackle similar issues for those microwave radiometers not capable of in-orbit backlobe maneuvers and receiving the radiances inevitably from the outer edge of the hot-load or cold-sky reflectors.