Design, construction, and calibration of a portable short wave infrared spectroradiometer

This dissertation describes the design, construction, and calibration of a portable short wave infrared (SWIR) spectroradiometer. The main use for the instrument is the collection of ground reflectance and radiance data for the radiometric calibration of operational and proposed high spectral resolution remote-sensing systems, such as the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS), the Moderate Resolution Imaging Spectroradiometer (MODIS), the High Resolution Imaging Spectrometer (HIRIS), and the Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER). The instrument will also be used for cross calibrating Earth Observing System (EOS) calibration facilities and for a variety of high spectral resolution studies in earth science. The instrument is designed to be carried as a backpack unit, on a vehicle, or in a helicopter or airplane. The spectroradiometer covers the range from 1.05 to 2.45 {dollar}mu{dollar}m. The spectral sampling interval is 1.37 nm and the spectral resolution is variable from about 5 nm to more than 100 nm. A single spectrum can be acquired in as little as 1 s. The signal-to-noise ratio (SNR) for a single 1-s scan is about 90 at a wavelength of 2.2 {dollar}mu{dollar}m for a lambertian surface of 100% reflectance illuminated by the sun at normal incidence with 14-nm spectral resolution, a 25{dollar}spcirc{dollar} background temperature, and no atmospheric attenuation. The SNR can be improved by averaging multiple scans. Field-of-view defining optics are coupled by a flexible fiber optics bundle to the spectroradiometer, which consists of a non-scanning concave holographic diffraction grating with flat focal field imaged onto a 1024-element liquid-nitrogen-cooled PtSi linear-array detector. The combination of concave grating and linear-array detector was chosen in preference to Fourier transform, Hadamard transform, and scanned grating monochromator systems on the basis of simplicity, high SNR, and greatest radiometric accuracy.