Solar radiation over and under sea ice was measured by radiation station 2020R15, an autonomous platform, installed on drifting First-Year-Ice (FYI) in the Arctic Ocean during MOSAiC (Leg 4) 2019/20. The resulting time series describes radiation measurements as a function of place and time between 13 July 2020 and 19 July 2020 in sample intervals of 3 hours. The radiation measurements have been performed with spectral radiometers. All data are given in full spectral resolution interpolated to 1.0 nm, and integrated over the entire wavelength range (broadband, total: 320 to 950 nm). Two sensors, solar irradiance and upward reflected solar irradiance, were mounted on a on a platform about 1 m above the sea ice surface. The third sensor was mounted 0.5 m underneath the sea ice measuring the downward transmitted irradiance.This buoy had no own GPS source. It was located at the Central Observertory (CO2) of MOSAiC. The drift track of CO2 is published here: Nicolaus, Marcel; Riemann-Campe, Kathrin; Bliss, Angela; Hutchings, Jennifer K; Granskog, Mats A; Haas, Christian; Hoppmann, Mario; Kanzow, Torsten; Krishfield, Richard A; Lei, Ruibo; Rex, Markus; Li, Tao; Rabe, Benjamin (2021): Drift trajectory of the Central Observatory 2 (CO2) of the Distributed Network of MOSAiC 2019/2020. Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, PANGAEA, https://doi.org/10.1594/PANGAEA.937186