FY-3A中分辨率光谱成像仪红外通道辐射定标的场地评估

Evaluation for radiometric calibration of infrared band of FY-3A medium resolution spectral imager(MERSI) using radiometric calibration sites

对比分析了基于场地观测数据模拟的和FY-3A中分辨率光谱成像仪(MERSI)红外通道星上定标观测卫星入瞳亮温值。主要的场地观测数据来自于2008、2009年青海湖以及2010年敦煌外场同步观测和2008、2009年青海湖浮标观测。利用光学仪器的同步观测数据共有7组有效结果,两年的青海湖有效浮标数据一共18组。通过对比分析发现,MERSI观测结果基本都在夜间低于浮标同步观测结果,而白天偏高。综合与场地同步和浮标的对比结果发现,MERSI星上定标观测亮温值系统性偏高于基于场地观测数据模拟的亮温值,平均偏高1.72±1.18 K。MERSI星上定标观测亮温值的系统性偏高可能主要由星上黑体发射率未经过修正引起。

This investigation compared the brightness temperatures observed by infrared band of FY-3A MERSI using on-board radiometric calibration coefficients with that simulated surface observation data. The primary surface data were collected from the simultaneous observation in Qinghai Lake site in 2008, 2009 and Dunhuang site in 2010, and buoy data in Qinghai Lake site in 2008 and 2009. Seven and eighteen groups of available data from the simultaneous observation data using optical instruments and buoy data in Qinghai Lake were used. It was found that the observed brightness temperatures by medium resolution spectral imager（MERSI） sensor were basically higher than the results derived from buoy data at nighttime, and the results were opposite at daytime. To sum up, the results from both simultaneous observation andbuoy data indicate that the brightness temperatures observed by MERSI sensor are 1.72±1.18 K, which are systematically higher than the simulated results using surface observation data, which is mainly attributed to the variations of emissivity of on-board blackbody without calibration.