Calibration of Satellite Low Radiance by AERONET-OC Products and 6SV Model

Cristiana Bassani,Sindy Sterckx

doi:10.3390/rs13040781

Abstract

For water quality monitoring using satellite data, it is often required to optimize the low radiance signal through the application of radiometric gains. This work describes a procedure for the retrieval of radiometric gains to be applied to OLI/L8 and MSI/S2A data over coastal waters. The gains are defined by the ratio of the top of atmosphere (TOA) reflectance simulated using the Second Simulation of a Satellite Signal in the Solar Spectrum—vector (6SV) radiative transfer model, REF, and the TOA reflectance acquired by the sensor, MEAS, over AERONET-OC stations. The REF is simulated considering quasi-synchronous atmospheric and aquatic AERONET-OC products and the image acquisition geometry. Both for OLI/L8 and MSI/S2A the measured TOA reflectance was higher than the modeled signal in almost all bands resulting in radiometric gains less than 1. The use of retrieved gains showed an improvement of reflectance remote sensing, Rrs, when with ACOLITE atmospheric correction software. When the gains are applied an accuracy improvement of the Rrs in the 400–700 nm domain was observed except for the first blue band of both sensors. Furthermore, the developed procedure is quick, user-friendly, and easily transferable to other optical sensors.

Highlights

The management and monitoring of the coastal environment benefit from satellite products providing systematic measurements suitable for mapping whole ecosystems at different scales [1]
The radiative transfer in the atmosphere–water system is modeled by reliable codes such as Second Simulation of a Satellite Signal in the Solar Spectrum (6SV) [10,11,12,13,14] and the MODerate resolution atmospheric TRANsmission (MODTRAN) [15], with inputs to describe the system and the imaging geometry of acquisition
The results show diffusely the validity of the the Belharmony low-radiance gains derivedasinreported this study component reflected towards sensor, not considered in the model ininterms of the Rrs obtained by the atmospheric correction of Operational Land Imager (OLI)/L8 andduring

Summary

Introduction

The management and monitoring of the coastal environment benefit from satellite products providing systematic measurements suitable for mapping whole ecosystems at different scales [1]. The approaches for calibration and validation purposes are mostly based on the unsupervised in situ measurements acquired by ground-based automated radiometers [3,4] and on modeling the atmospheric–water radiative transfer [5,6]. Concerning the in situ measurements of the current satellite missions, the accurate satellite products supplying drove the European Space Agency (ESA) to fund Fiducial Reference Measurements (FRM) projects to provide independent unsupervised measurements for vicarious calibration system (VCS) in addition to the validation component such as the latest FRM4SOC project [16]. New European infrastructures will be built to enlarge the unsupervised measurements [17,18] available for calibration and validation purposes [19] as required by the European system for monitoring the Earth (Copernicus) [20]

Methods

Results

Discussion

Conclusion