A software tool for end-to-end simulation of data products of spaceborne and airborne visible, near-infrared and short-wave infrared imaging spectrometers, starting from either synthetic or airborne hyperspectral data, has been developed and tested. Such a simulator is conceived as a preliminary aid tool (during phase 0/A ) for the specification and early development of new Earth observation optical instruments, whose compliance to user's requirements is achieved through a process of cost/performance trade-off. The proposed simulator is based on three different core modules: the reflectance scenario simulator, the atmospheric simulator, and the instrument simulator.The main novelty of this paper is that the modeling adopted for the simulator is validated and assessed through the matching of synthetized spectra, both radiance and reflectance, to true spectra measured on an agricultural clay bare soil by means of a hand-held point spectrometer and an airborne instrument developed and manufactured by Selex Galileo S.p.A. Both pure and mixed spectra show a high degree of matching between true and synthetic data, thereby establishing the validity of the underlying linear spectral mixing model. Furthermore, a validation of an application test has been performed for clay soil mapping at ground and airborne level. Eventually,a satellite instrument simulation of the same clay map has demonstrated a more than acceptable agreement notwithstanding the low spatial resolution.