The traditional approach for achieving hyperspectral imaging over a broad range of infrared (IR) wavelengths involves multiple focal plane arrays (FPAs), dispersive elements, and optical beamsplitters. It has been shown that the current state-of-the-art in dual-band infrared focal plane array (IRFPA) technology allows spectral imagery to be obtained in two wavebands simultaneously with a single FPA, therefore reducing cryo-cooler and power requirements. The new approach described here advances the capabilities of the current state-of-the-art one step further and achieves a spectrometer concept based on a tri-band IRFPA. The tri-band spectrometer concept would lead to spectral imagery collected simultaneously in the SWIR, MWIR, and LWIR spectral regions with high efficiency. To achieve this a unique characteristic of a dispersive grating, that of overlapping spectral orders, would be exploited to allow simultaneous focusing of three spectral bands onto the multi-waveband FPA, thereby creating co-registered spectral images. The capabilities of a multi-waveband FPA then allow integration of spectra independently in the various orders. In addition, spectral images would be perfectly registered both spatially and spectrally, a difficult prospect for the traditional approach. By providing hyperspectral imagery in the SWIR, MWIR, and LWIR spectral regions, we capture the bulk of reflected and thermally emissive target and background phenomenology, within the constraints of atmospheric transmission. The characteristics of a suitable tri-band FPA are derived on the basis of our modeling efforts.