ROSINA, the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis,
is a combination of two mass spectrometers and a pressure sensor.

    The mass spectrometers will determine the composition of the comet's atmosphere and 
    ionosphere, measure the temperature and bulk velocity of the gas and ions, and 
    investigate reactions in which they take part. 
    
    The ROSINA pressure sensor is capable of 
    measuring both total and ram pressure, and will be used to determine the gas density and 
    rate of radial gas flow.