Light is a major factor influencing physical, biological and chemical key processes in the upper water column. Satellite remote sensing is capable to assess spatial reflectance patterns, representing water color. Limiting factors are the spatial resolution of the single pixel, temporal resolution and the correction for atmospheric effects. Technical progress of the oceanographic (core) Argo floats towards biogeochemical platforms (BGC- or Bio-Argo) partly also provided information on light availability over depth. Limiting factors are however the spatial resolution, the low spectral information and the long-term stability of sensors lacking the possibility for post calibration. Therefore this proposal aims to 1) establish high resolution spectral measurements on Bio-Argo floats, 2) generate global information on the hyperspectral underwater light field, its temporal and spatial variability, contributing to recent satellite Cal/Val activities, 3) position ICBM in cooperation with BSH and GEOMAR and international partners within the international community addressing development and operation of bio-optical sensors on biogeochemical Argo floats, 4) foster innovative German sensor technologies within the international Argo program.