Radiative transfer models provide an explicit physical connec-tion between the observed remote sensing signal and the targetvariable (e.g., vegetation trait). The development and applica-tion of physically sound integrated models to reliably quantifyand discriminate between the atmospheric, soil, canopy and leafcontribution to reflected electromagnetic radiation is central foradvancing the field. However the inversion of models to retrievevegetation characteristics from canopy reflectance observations isaffected by the ill-posed inverse problem