One great advantage of optical hyperspectral remote sensing from unmanned aerial systems (UAS) compared to satellite missions is the possibility to fly and collect data below clouds. The most typical scenario is flying below intermittent clouds and under turbulent conditions, which causes tilting of the platform. This study aims to advance hyperspectral imaging from UAS in most weather conditions by addressing two challenges: (i) the radiometric and spectral calibrations of miniaturized hyperspectral sensors; and (ii) tilting effects on measured downwelling irradiance. We developed a novel method to correct the downwelling irradiance data for tilting effects. It uses a hybrid approach of minimizing measured irradiance variations for constant irradiance periods and spectral unmixing, to calculate the spectral diffuse irradiance fraction for all irradiance measurements within a flight. It only requires the platform's attitude data and a standard incoming light sensor. We demonstrated the method at the Palo Verde National Park wetlands in Costa Rica, a highly biodiverse area. Our results showed that the downwelling irradiance correction method reduced systematic shifts caused by a change in flight direction of the UAS, by 87% and achieving a deviation of 2.78% relative to a on ground reference in terms of broadband irradiance. High frequency (< 3 s) irradiance variations caused by high-frequency tilting movements of the UAS were reduced by up to 71%. Our complete spectral and radiometric calibration and irradiance correction can significantly remove typical striped illumination artifacts in the surface reflectance-factor map product. The possibility of collecting precise hyperspectral reflectance-factor data from UAS under varying cloud cover makes it more operational for environmental monitoring or precision agriculture applications, being an important step in advancing hyperspectral imaging from UAS.

与卫星任务相比，来自无人机系统 (UAS) 的光学高光谱遥感的一大优势是可以在云层下飞行和收集数据。最典型的场景是在间歇性云层下方和湍流条件下飞行，这会导致平台倾斜。本研究旨在通过解决两个挑战来推进 UAS 在大多数天气条件下的高光谱成像：(i) 小型化高光谱传感器的辐射测量和光谱校准；(ii) 倾斜对测量下流辐照度的影响。我们开发了一种新方法来校正倾斜效应的下流辐照度数据。它使用一种混合方法，将恒定辐照度周期和光谱分离的测量辐照度变化降至最低，计算飞行中所有辐照度测量的光谱漫射辐照度分数。它只需要平台的姿态数据和一个标准的入射光传感器。我们在哥斯达黎加的帕洛佛得角国家公园湿地展示了该方法，这是一个高度生物多样性的地区。我们的结果表明，下流辐照度校正方法将 UAS 飞行方向变化引起的系统偏移减少了 87%，并在宽带辐照度方面相对于地面参考实现了 2.78% 的偏差。由 UAS 的高频倾斜运动引起的高频 (< 3 s) 辐照度变化减少了 71%。我们完整的光谱和辐射校准以及辐照度校正可以显着消除表面反射系数图产品中典型的条纹照明伪影。在不同云层下从 UAS 收集精确高光谱反射系数数据的可能性使其更适用于环境监测或精准农业应用，这是推进 UAS 高光谱成像的重要一步。