1. A multi-mode imaging spectrometer comprising: a first entrance slit having a first orientation; a second entrance slit having a second orientation, the second orientation being substantially orthogonal to the first orientation; at least one dispersive element configured to spectrally disperse electromagnetic radiation and provide spectrally dispersed electromagnetic radiation; collimating and imaging optics configured to receive the electromagnetic radiation from the first entrance slit during a first mode of operation of the imaging spectrometer and from the second entrance slit during a second mode of operation of the imaging spectrometer, and to direct the electromagnetic radiation to the at least one dispersive element; at least one imaging detector configured to receive the spectrally dispersed electromagnetic radiation and produce image data therefrom, the collimating and imaging optics being further configured to direct and focus the spectrally dispersed electromagnetic radiation onto the at least one imaging detector; and a processor coupled to the at least one imaging detector and configured to receive and process image data from the at least one imaging detector and to select one of the first and second modes of operation of the multi-mode imaging spectrometer responsive to processing the image data.