The Effects of Solar Irradiance Spectra on Calculation of Narrow Band Top-of-Atmosphere Reflectance

Abstract

Extraterrestrial solar irradiance spectra detail the solar energy distribution over wavelengths, and numerous solar irradiance models are available within the remote sensing community. However, reference spectra may differ widely owing to differences in solar activity, measurement instruments and calibration. Six widely referenced solar spectra were selected in this work to examine their differences and the impacts of these differences on calculations of narrow band top-of-atmosphere reflectance using MERIS and Hyperion hyperspectral sensor spectral configurations. Mean solar exoatmospheric irradiance (MSEI) was computed using the different solar irradiance models and spectral response functions of the MERIS and Hyperion hyperspectral sensors. Then, the effects of MSEI on top-of-atmosphere (TOA) reflectance and the normalized difference vegetation index (NDVI) and atmospherically resistant vegetation index (ARVI) were investigated. The results show that the six selected solar irradiance models have significant differences from 350 to 2500 nm, which in turn result in differences in the MSEI derived from MERIS and Hyperion observations. These differences have a less significant effect on the TOA reflectance in the visible and near-infrared bands and on NDVI. However, the differences result in large differences in TOA reflectance in the infrared bands and in ARVI.

The Impact of Choice of Solar Spectral Irradiance Model on Atmospheric Correction of Landsat 8 OLI Satellite Data

“…Despite the observed low variability (other than Sun-Earth distance) of the spectral solar constant in spectral regions used for recent Earth observation (roughly 400-2600 nm), it has been observed that there are considerable differences between the commonly available estimates. For example, Zhang et al [8] studied the effects of using selections of spectral solar constant from six older models and found significant differences in the calculation of indices. They suggested the Thuillier model [4] seemed to be most accurate but found it hard to evaluate what establishes a "best" model.…”

Quantifying the Impact of Solar Spectra on the Inter-Calibration of Satellite Instruments

“…As noted in the introduction, previous studies [17,[20][21][22] have reported noticeable differences between these solar spectra that can be larger than their reported uncertainties. The state-of-the-art TSIS-1 SIM observations (Section 2.1.7) have order-of-magnitude reductions in uncertainty (<0.3% over the majority of the spectrum) relative to predecessor instruments, justifying our use of the TSIS-1 SIM as the baseline for comparing the other solar spectra against.…”

“…The VIIRS instrument on board the Suomi-National Polar-orbiting Partnership (SNPP) spacecraft, however, utilizes the Kurucz spectra [17,18] from MODTRAN 4.0 [16,19]. Previous studies [16,[20][21][22] have reported noticeable differences between these solar spectra that can potentially lead to incompatible retrievals from these satellite datasets.…”

Effects of solar noise on the detection range performance of a laser spot tracker

“…The solar spectral irradiance measured at the ground increases from wavelengths of 350 to 500 nm to a maximum value of approximately 2250 Wm −2 μm −1 near 460 nm and then decreases above 500 nm to approximately 40 Wm −2 μm −1 at a 2400-nm wavelength. 9 The direct clear-sky irradiance regarding the altitude is expressed as follows: 10 E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 1 ; 1 1 6 ; 2 8 5…”