Abstract: Disclosed is a method for spectrally unmixing spectral data originating from a set of spectral sources and including a series of one or more optical spectra. The method can include modeling the spectral data using an endmember matrix and an abundance matrix, the endmember matrix including a set of endmember spectra respectively corresponding to the set of spectral sources, and the abundance matrix indicates an abundance of each endmember spectrum in each spectrum. The method can also include providing external prior spectral information comprising prior endmember information and prior abundance information conveying at least partial prior knowledge about the endmember matrix and the abundance matrix, respectively, and performing a spectral unmixing operation on the spectral data to determine a solution for the endmember and abundance matrices, using the external prior spectral information as input.