RSI

RSI (Radio Science Investigation). Frequency shifts in the spacecraft's radio signals will be used to measure the mass and gravity of the comet nucleus in order to deduce its density and internal structure, to define the comet's orbit, and to study its inner coma. RSI has already determined the mass and density of the asteroid Lutetia during the flyby in 2010, and studied the solar corona during the periods when the spacecraft, as seen from Earth, was passing behind the Sun (in 2006 and 2010).