Toward a long-term consistent data record of Aerosol and Surface Reflectance from SPOT-VGT and PROBA-V missions

Abstract

PROBA-V mission was conceived, and launched by ESA in 2013, to ensure continuity to the SPOT - VGT longterm data series of global daily land observations, started in 1998, bridging the gap to Sentinel-3. Nowadays, thanks to the successful and smooth operations of the PROBA- V satellite, a >20 years consistent data record of land surface reflectances, is available to the scientific community. This long-term dataset has clear relevance for trend analysis, anomaly detection and climate related applications. Despite this obvious interest, the exploitation of this dataset is still limited and mostly focused to near-real time applications, using the SPOT - VGT archive as a background average to detect anomalies, e.g., in NDVI time series. In order to fill this gap, and to exploit the full potential of this dataset, ESA has funded a new project called CISAR@MEP, whose primary goal is to set the stage for the generation of a global 20 years long-term data record of surface reflectance and aerosol properties from analysis of SPOT-VGT and PROBA-V observations. For this purpose, a recently developed algorithm, called CISAR and developed by Rayference, will be used, allowing the joint retrieval of aerosol and surface reflectance properties, together with the associated retrieval uncertainties. This new long-term data record will eventually fulfill current Global Climate Observing System (GCOS) requirements for the generation of Essential Climate Variables (ECVs), such as surface albedo and aerosol optical thickness, being 5% and 10%, respectively. Such data set can support the needs of both the atmospheric and land surface research communities and it can contribute to Copernicus operational service and ESA Climate Change Initiatives (CCI) activities. The CISAR@MEP project started during Q1 2019 with expected 2 years duration. The aim of this paper is to present this ESA funded project, to illustrate the objectives and the methodology and to provide some preliminary results. Furthermore, the technological implementation approach will be detailed, which makes full use of the PROBA-V Mission Exploitation Platform (MEP), a scalable processing environment, providing direct access to both SPOT-VGT and PROBA-V full mission archive together with the required resources and tools.