DART model is one of the most comprehensive and accurate radiative transfer (RT) models to simulate remotely sensed signals in the Earth-atmosphere system. Its standard RT modelling mode, called DART-FT, relies on the discrete ordinates method. Its recently developed Monte Carlo mode using an unbiased bidirectional path tracing method, called DART-Lux, increases hundredfold DART efficiency to simulate images. Since DART-Lux does not simulate yet atmospheric RT, a hybrid method has been designed to accurately and fast simulate remote sensing images at top of atmosphere (TOA). It couples the atmospheric RT modelling of DART-FT with the very efficient Earth surface RT modelling of DART-Lux. For that, a new sky light modelling, an innovative BRF camera modelling and an adapted radiative coupling framework have been designed. The efficiency and accuracy of this hybrid method have been validated using DART-FT as a reference. Here, we present this validation for a realistic forest stand. Simulation time is reduced by a factor of 750 with a relative difference of solar plane reflectance factor smaller than 1%. This hybrid method opens new perspectives for the use of 3D modelling in remote sensing applications. It is already part of the DART version freely available for scientists (https://dart.omp.eu).

DART模型是用于模拟地球大气系统中遥感信号的最全面，最准确的辐射传输（RT）模型之一。其标准RT建模模式称为DART-FT，它依赖于离散纵坐标方法。它最近开发的蒙特卡洛模式使用称为DART-Lux的无偏双向路径跟踪方法，将模拟图像的DART效率提高了数百倍。由于DART-Lux尚不能模拟大气RT，因此已设计了一种混合方法来准确快速地模拟大气（TOA）顶部的遥感图像。它将DART-FT的大气RT建模与DART-Lux的非常高效的地球表面RT建模结合在一起。为此，已经设计了新的天光建模，创新的BRF摄像机建模和经过调整的辐射耦合框架。使用DART-FT作为参考，已经验证了这种混合方法的效率和准确性。在这里，我们提出了对真实森林林的验证。模拟时间减少了750倍，而太阳平面反射系数的相对差小于1％。这种混合方法为3D建模在遥感应用中的使用开辟了新的前景。它已经成为可供科学家免费使用的DART版本的一部分（https://dart.omp.eu）。