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; a first dispersive element and a second dispersive element each 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 wherein in the first mode of operation the collimating and imaging optics are further configured to direct the electromagnetic radiation from the first entrance slit to the first 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, in the first mode of operation, focus the spectrally dispersed electromagnetic radiation from the first dispersive element onto the at least one imaging detector; a movable fold mirror, wherein in the second mode of operation the movable fold mirror is positioned in an optical path between the collimating and imaging optics and the second dispersive element, the collimating and imaging optics being further configured to, in the second mode of operation, direct the electromagnetic radiation from the second entrance slit to the movable fold mirror, the fold mirror being further configured to reflect the electromagnetic radiation from the collimating and imaging optics to the second dispersive element, and to reflect the spectrally dispersed electromagnetic radiation from the second dispersive element to the collimating and imaging optics, and the collimating and imaging optics being further configured to focus the spectrally dispersed electromagnetic radiation from the fold mirror 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, responsive to processing the image data, select one of the first and second modes of operation of the multi-mode imaging spectrometer.