First Retrievals of Aerosol Optical Thickness and Surface Reflectance using EnMAP Radiance Data with the XBAER Algorithm

We present work and results of the XBAER4EnMAP project, which focuses on the adaptation and further development of the mature eXtensible Bremen Aerosol/cloud and surfacE parameters Retrieval (XBAER) algorithm for the HyperSpectral Imager (HSI) instrument on board the Environmental Mapping and Analysis Program (EnMAP) satellite mission.

The XBAER algorithm retrieves aerosol optical thickness (AOT), surface reflectance (SRF) and cloud parameters and was previously developed using radiance data from both the MEdium Resolution Imaging Spectrometer (MERIS) onboard Envisat and the Ocean and Land Colour Instrument (OLCI) onboard Sentinel 3, both of which provide radiance data at a spatial resolution of 300m to 1.2km.

We aim to update XBAER to utilize EnMAP's higher spatial resolution radiance data of 30m, and to produce equivalent spatial-resolution data products with it. We present a comparison of OLCI and EnMAP top of atmosphere reflectances (RTOA) for co-located pixels, demonstrating that EnMAP is well calibrated enough for use in the XBAER algorithm. We then present results of comparison of XBAER-derived surface reflectance (SRF) and AOT using the same co-located pixels, i.e. at OLCI spatial resolution. Furthermore, we present first results of high-spatial resolution XBAER AOT, including a preliminary comparison with AErosol RObotic NETwork (AERONET).

Finally we discuss remaining challenges, such as updating XBAER's cloud mask and surface treatment for high spatial resolution data, and how to best compare AOT retrieved for the the small EnMAP scene size to AOT retrieved from point sites.