A prototype of a compact, low mass, multispectral imaging spectrometer suitable for space-based applications
has been built utilizing a dual-band infrared focal plane array. The spectrometer design uses a grating blaze
chosen to be efficient at both 3.75-6.05 and 7.5-12.1 μm. The spectrometer had previously been spectrally
calibrated with flooded blackbody illumination and the mercury cadmium telluride focal plane array was found
to have cutoff wavelengths near 5.2 and 10.5 μm. The spectrometer was tested in the MWIR band by imaging a
blackbody at a distance of 100 m. Spectral images of the Sun were obtained in both MWIR and LWIR, allowing
comparison of the solar diameter at various IR wavelengths with tabulated visual widths. The performance of
the spectrometer is characterized at a deeper level as a result of these observations.