SPAR@MEP aims to derive a consistent SPOT-VEGETATION and PROBA-V Aerosol and Surface Reflectance long-term data record in the PROBA-V Mission Exploitation Platform (MEP). The projects deliverables will consist on a Long Term Data Record (1998-2018) of Aerosol Optical Thickness (AOT) and Bidirectional Reflectance Factor (BRF) at 1Km of resolution over selected key macro regions around AERONET stations and on a global processing of about 5 years at a spatial resolution suitable for climate studies (e.g., 5km). The target processing facility will be the Proba-V MEP. The radiometric accuracy and multi-temporal stability of the considered long-term data record, which was acquired with three different radiometers (SPOT-4, SPOT-5 and Proba-V), should be carefully assessed as a first verification step for the project. Furthermore, the processing performances should be significantly improved in order to sustain the mission reprocessing. To this end, the current plan is to exploit multi-cores CPU, or, alternatively, the GPU technology. Both parallel processing with CPU multi-cores and GPU servers are available on the MEP to support this project.
The comprehensive PV-LAC feasibility study demonstrated the possibility to apply the CISAR algorithm on PROBA-V data for the joint retrieval of surface reflectance and aerosol optical properties. On top of that, under the conxtext of the CIRCAS study the CISAR algorithm has been modified to also retrieve cloud optical thickness and can therefore can be run without the need of an external cloud mask.
Information about the satellites products
PROBA-V was developed as both a follow-up to the 15-year SPOT-VEGETATION mission, as well as a preparation for the recently launched ESA Sentinel-3 land and ocean observation satellite mission. The SPOT-VEGETATION mission provided essential information on e.g. crop yields, droughts, and deforestation to a broad user community.
To optimally serve the vegetation and land surface community, PROBA-V’s spectral channels are similar to those of the SPOT-VGT instrument, thereby preserving a maximum of observational consistency with the SPOT-VGT era. Benefiting from the technological developments since the SPOT-VEGETATION launch in 1998, PROBA-V has a lean instrumental payload on a platform smaller than a cubic meter. Using a constellation of 3 cameras, PROBA-V covers the entire Earth every two days and provides useful reflectance measurements for climate impact assessment, surface water resource management, agricultural monitoring, and food security purposes.
PROBA-V has been developed by a full Belgian consortium, see the Partners section for more details.
The CISAR algorithm
The CISAR algorithm relies on the FASTRE radiative transfer model that describes surface reflectance and atmospheric absorption/scattering processes. The lowest level represents the surface. The lower layer hosts the aerosols. Molecular scattering and absorption are also taking place in that layer which is radiatively coupled with the surface for both the single and the multiple scattering. The upper layer is only subject to molecular absorption.
The inversion of the FASTRE model within the CISAR algorithm against satellite observations provides accurate estimates of the surface reflectance field, aerosol or cloud optical thickness and single scattering properties in each processed spectral band. An estimate of the retrieval uncertainty is also provided.
As the proposed method retrieved both cloud and aerosol properties with the same retrieval algorithm, no cloud mask is needed to perform the retrieval. Additionally, the same algorithm can be applied over any type of surfaces, including dark or bright surfaces or water bodies.
SPAR@MEP is funded by the European Space Agency (ESA) with the following Contract No. 4000128001/19/I-NS