Opto-mechanical design and calibration of a hyperspectral irradiance monitor

A hyperspectral irradiance monitor (HIM) is designed to measure the direct solar spectral irradiance on the ground, which can be used for research on climate change and vicarious calibration. The spectrometer uses a Féry prism to disperse and converge light, and a linear image sensor (NMOS) measures the spectral irradiance ranging from 400 nm to 1100 nm. The instrument utilizes two flat mirrors to fold the optical path, and optical software is used to optimize the key parameters. The dispersion equation of the prism and two characteristic wavelengths of the laser are utilized for the spectral calibration, for which the uncertainty of the spectral calibration is less than 0.8 nm. A standard lamp is used for the spectral irradiance calibration, for which the uncertainty of the spectral irradiance calibration is less than 2.78% (k=2). The instrument runs stably in the field.