Lake water level estimated by a purely radiometric measurement: An experiment with the SLSTR radiometer onboard Sentinel-3 satellites

This work describes a preliminary study on the possible usage of the imaging radiometer SLSTR (Sea and Land Surface Temperature Radiometer) onboard the Sentinel-3 satellites for estimating quantitative parameters (extent and/or level) of inland water bodies. Various works in the literature propose a combination of optical imagery and radar altimetry to estimate water storage variations in inland water targets. This work wants to exploit the simultaneous acquisition offered by SRAL (Synthetic aperture Radar ALtimeter) and SLSTR instruments hosted by the Sentinel-3A/B platform. We present a practical case study, demonstrating how a strongly reduced subset of radiometric measurements can be enough representative of the status of the natural system under observation. In our approach, a subset of the collected radiance maps is extracted, based on the selection of the most variable pixels. Thus, a time series of average spectral radiances is built upon the reduced set of SLSTR data, and compared with satellite radar altimetry measurements. Preliminary results show a promising relationship between the timeseries generated by the two independent instruments, in terms of both general trend and seasonal dependence. Finally, by using the approximation proposed in this paper, a very light computational process can infer an estimation of water storage, when the natural system is fully identified on the basis of ground-truth data.