Following the past TropiScat and AfriScat tower-based scatterometer experiments conducted as part of the European Space Agency (ESA) BIOMASS mission preparation activities, a follow-up experiment referred to as TropiScat-2 has been undertaken since March 2018 in French Guiana. The main objectives of this new campaign consist in extending the previous time series at P and L bands, and also in investigating the possible synergies between P, L and C-band measurements thanks to the quasi-simultaneous multi-frequency acquisitions provided by the new instrument. In this paper, the differences between temporal decorrelation at P, L and C-bands are specifically analyzed based on a 67-day time series dating back to early August 2018. This study confirms previous results conducted at P and L-bands, with a specific focus here on the importance of the diurnal cycles and on the updated acquisition scenarios for the upcoming BIOMASS mission. Interestingly, this study also reveals the diurnal cycles at C-band, although the coherence values are much lower than those at P and L-bands. In addition to enhancing scientific insights regarding our understanding of microwave interactions, this study provides key figures for the design of new satellite missions.