Products and Applications for inland and coastal WATER for PRISMA hyperspectral imagery: the PANDA-WATER project

The quality and ecological status of Inland and coastal waters (ICWs) is a key worldwide issue because of the multiple and conflicting pressures from anthropogenic perturbation and environmental change. Timely monitoring of ICWs is therefore necessary to enhance our understanding of their functions, the drivers impacting on them, and to deliver effective management. Earth Observation (EO) may be used for acquiring timely, frequent synoptic information from local to global scales of ICWs. EO data have been successfully applied for mapping waterbodies for decades, even though the current satellite radiometers are designed for observing the global ocean (e.g. Sentinel-3 OLCI), or land surface (e.g. Sentinel-2 MSI, Landsat 8 OLI, Landsat 9 OLI-2) and not specifically suited for observing processes and phenomena occurring in ICWs. These aquatic ecosystems can be a mixture of optically shallow and optically deep waters, with gradients of clear to turbid and oligotrophic to hypertrophic productive waters and varying bottom visibility with and without the presence of aquatic vegetation (floating or submerged). Deriving ICW quality products from the existing sensors thus remains challenging, due to their optical complexity, as well as the spatial and temporal resolution of the imagery. PRISMA (PRecursore IperSpettrale della Missione Applicativa), the new hyperspectral satellite sensor of Italian Space Agency (ASI) in orbit since March 2019, provides data with high spectral resolution and good radiometric sensitivity able to resolve small changes in the signal relative to the noise of the sensor and the atmosphere (i.e., high radiometric resolution and high signal to noise ratio). Moreover, the spatial and spectral resolutions of the PRISMA are well suited for the retrieval of multiple biophysical variables, such as optically active water constituents (chlorophyll, suspended and coloured dissolved organic matter) and phycocyanin. The PANDA-WATER project (PRISMA Products AND Applications for inland and coastal WATER), funded by ASI, aims to demonstrate the capabilities of PRISMA hyperspectral imagery to measuring ICWs and to evaluate its suitability and gaps to address inland and coastal ecosystem science and management challenges. The overall objective of PANDA-WATER is to provide a set of innovative and validated products, derived from imaging spectrometry, that enables the retrieval of additional variables of interest for inland and coastal ecosystems. The novelty of the PANDA-WATER products will stem from the application of the state-of-the-art-algorithms adapted to the ICWs to the PRISMA increased spatial, spectral and radiometric resolution, thus resulting in augmented observational capabilities and lower associated uncertainties compared to the current Copernicus missions. These products will range from more accurate estimates of optically active water constituents, to more sophisticated products such as particle size distributions or distinguishing sources of suspended and coloured dissolved matter, water depth, natural or artificial materials floating over the surface, attenuation coefficient and euphotic depth, the presence of cyanobacteria and harmful algal bloom. The product development carried out within PANDA-WATER from PRISMA data will also be suitable for the upcoming hyperspectral missions (i.e. DLR EnMap, Copernicus CHIME, NASA's PACE and SBG), thus contributing to the global advance in spaceborne imaging spectrometry.