A field-portable thermal infrared grating spectrometer (THIRSPEC)

A thermal infrared grating spectrometer was developed for field studies in the Earth sciences. The design is based on a reflection grating and a 60-element HgCdTe detector array. The useful spectral range of the instrument covers 7.9-11.3 /spl mu/m with a Nyquist limited resolution of 0.16 /spl mu/m. The instrument averages over a 12/spl deg/ field of view and compares the exitance of the target to that of an internal black body at ambient temperature. The noise equivalent temperature is approximately 0.06/spl deg/K over the useful spectral range. Background radiance reflected from the surface of the target can seriously impede the determination of emissivity. This effect is removed from the spectra of geological samples by the use of reference samples.< >