Spectroradiometer spectral calibration, ISRF shapes, and related uncertainties

Abstract

A key characteristic of a spectroradiometer is the instrumental spectral response function (ISRF) that is determined during spectral characterization and calibration. The response shape of the ISRF is commonly assumed to be Gaussian, though this is known to not always be the best description. We show that in the context of laboratory calibration, the largest source of uncertainty lies in the ISRF assumption. We perform the spectral calibration of laboratory measurements obtained with four analytical spectral device field spectroradiometers using several different ISRF “modes” to investigate their respective fitting performance, and examine the impact of choosing an ISRF that differs from a Gaussian when calibrating a MODTRAN6 spectrum. Finally, we conduct the uncertainty analysis of our calibration by propagating uncertainty via a Monte Carlo method.

Uncertainty Support in the Spectral Information System SPECCHIO

“…1) uses emission line lamps where the wavelengths of the emission peaks are given in the Atomic Spectra Database by the National Institute of Standards and Technology (NIST) [32]. The SRF parameters are extracted through a process, which we describe in detail in Trim et al [33]. The important point is that the uncertainty of the SRF is produced by uncertainty propagation through the spectral calibration algorithm and is thus traceable to NIST [32].…”

“…The important point is that the uncertainty of the SRF is produced by uncertainty propagation through the spectral calibration algorithm and is thus traceable to NIST [32]. The SRF is parameterised by centre wavelength (CW), shape (s) and width (w), defining a Symmetric Super Gaussian sensitivity function which has been shown to better approximate the true SRF shape for some spectrometers [33]. The SRF has a combined uncertainty u(SRF), computed by propagating u(CW), u(s) and u(w).…”

Uncertainty Budget for a Traceable Operational Radiometric Calibration of Field Spectroradiometers, Calibration of the Heliosphere

“…The spectral calibration establishes the centre wavelength per detector element as a minimum but should also provide the spectral sensitivity per element in the form of a spectral response function. Recent algorithms allow the retrieval of such response functions beyond their traditional Gaussian parameterisation [11]. The subsequent radiometric calibration 2 > REPLACE THIS LINE WITH YOUR MANUSCRIPT ID NUMBER (DOUBLE-CLICK HERE TO EDIT) < is used to establish the relationship between the at-sensor radiance (L) and the corresponding Digital Numbers (DN) recorded by the instrument.…”