多光谱相机在轨绝对辐射定标是其遥感数据定量化应用的关键环节。高空间分辨率多光谱相机基于大面积灰阶靶标的在轨辐射定标, 以灰阶靶标BRDF、漫射/总辐射比和大气光学厚度等参数的地面测量为主, 通过目标反射辐射与大气程辐射、周围环境辐射的分离, 消除了对气溶胶散射的假设, 简化了定标流程, 突破了基于大面积均匀场定标受到的地理位置和天气状态等条件限制, 该方法有望实现高空间分辨率多光谱相机全动态范围内的高频次、高精度业务化在轨辐射定标。不确定度分析表明, 目前该辐射定标方法可实现4.7%的不确定度, 将来有望提高到3%—4%的水平。对天绘一号多光谱相机进行了基于大面积灰阶靶标的定标试验, 通过两次过顶时刻地面总辐照度变化的比较及靶标观测值的回归分析, 初步判断两次定标时间内多光谱相机波段3的性能发生了变化。
In-fl ight absolute radiometric calibration is one of the critical techniques for quantitative remote sensing. High spatial resolution remote sensor based on large area of gray-scale tarps vicarious calibration method relies on traps BRDF, diffuse global ratio and atmospheric optical thickness measurement, the calibration approach could isolated the DN signal created by the traps from the response produced by background radiance sources, which simplify the calibration process and eliminating the assumption of aerosol scattering. Uncertainty analysis showed that the calibration uncertainty is 4.7% at present, and could improve to 3%—4% in the near future. We describe the rationale, methods, and results of a large area gray-scale tarps based vicarious calibration campaign that was conducted between July and August, 2011. Through regression analysis of the observed values of the target and total irradiance of the two days, initially to determine the performance of band 3 might changed.