The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose, liquid scintillator-based neutrino experiment under construction in China. It is expected to be completed by the end of 2023 and the data taking is expected to continue for at least a decade. The primary goal is the determination of the neutrino mass ordering via measurement of reactor antineutrinos with 53 km badseline. Thanks to its unique 20 kton target mass and excellent energy resolution, JUNO has a vast potential in several areas of the neutrino and astroparticle physics. The physics reach of JUNO strongly depends on the quality and radio-purity of the liquid scintillator. Online Scintillator Internal Radioactivity Investigation System (OSIRIS) will monitor these properties during the months-long filling of the JUNO central detector and our group is responsible for its calibration.