An airborne hyperspectral scanning system with a reflective telecentric relay including a system housing fore-optics, mounted in the housing, an imaging spectrometer mounted in the housing, the imaging spectrometer comprising a spectrometer slit, the spectrometer slit having an exit side and an entrance side, a focal plane array, a fold mirror, and at least three spectrometer mirrors, ordered sequentially, and in optical alignment with each other, and a reflective telecentric relay, mounted in the housing between the fore-optics and the imaging spectrometer, the reflective telecentric relay comprising a collimator module, a scanning mirror module, and an objective module, the objective module being situated to receive intermediate image from the fore-optics and reflect a collimated beam to the scanning mirror image between the collimator module and the objective module, wherein the objective module is situated to form a telecentric image at the entrance of the spectrometer slit.