Earth Observation (EO) data primarily appears in the form of maps. However, these map products require the development of electromagnetic measurements, spectrometric algorithms and space missions. Between 2018 and 2022, I established a research group at Eawag that has been involved, to varying degrees, in all of these activities. In this seminar talk, I look back at results from my tenure track period.

Advances in hydro-optical measurement technology enable improving spectral and directional resolutions, and the handling of sensors for measuring radiance, absorption and scattering is improving to the point of automation. Eawag and EPFL have measured a unique data set of these parameters using a profiler at the LéXPLORE platform in Lake Geneva. This has enabled us to derive the sun-induced fluorescence of phytoplankton in the diurnal and annual cycle, and to gain new insights into non-photochemical quenching.

ESA regularly launches new experimental EO missions, so-called Earth Explorers. Understanding bio-optical processes such as non-photochemical quenching helps to define requirements for such missions. In 2020, we proposed the Global Assessment of Limnological, Estuarine and Neritic Ecosystems (GALENE) mission. This mission envisaged a combination of a cloud scanner and a pointing spectrometer. The implementation was developed jointly with Thales Aerospace, but the technology was found not to be space-ready.

Within the requirements they fulfil, existing and historical EO missions allow surveys of the variability of water quality in lakes and rivers. Based on Envisat (2002-2012), we determined candidate regime shifts in 1000 lakes worldwide. At regional scale, we documented the extent of a mine tailings spill in the DRC (see also Eawag News, April 13). Various case studies on Lake Geneva complement our efforts to improve the interpretation of EO data by combining it with hydrodynamic models and in situ measurements.