CALIBRATION AND PERFORMANCE EVALUATION OF A PORTABLE SHORTWAVE INFRARED (1.05-MU-M TO 2.45-MU-M) SPECTROMETER

A portable shortwave infrared (SWIR) spectrometer has been developed t hat covers the range from 1.05 to 2.45 mu m. The spectral sampling int erval is 1.37 nm, and the spectral resolution can be varied from about 5 nm to more than 100 nm. A single spectrum can be acquired in as lit tle as 1 s. The signal-to-noise ratio (SNR) for a single 1-s scan is a bout 100 at a wavelength of 2.2 mu m for a lambertian surface of 100% reflectance illuminated by the sun at normal incidence with 14-nm spec tral resolution. The SNR at 1.25 mu m is about 900 for the same condit ions. The estimated la uncertainty in the absolute radiometric calibra tion of the instrument is 2% to 3%. Field-of-view defining optics are coupled by a flexible fiber optic bundle to the spectrometer, which co nsists of a nonscanning concave holographic diffraction grating with a flat focal field imaged onto a 1024-element liquid nitrogen cooled Pt Si linear array detector. The primary use for the instrument is the co llection of ground reflectance and radiance data for the radiometric c alibration of operational and proposed high spectral resolution remote sensing systems.