Rosetta/ROSINA observations of the volatiles in the coma of comet 67P/Churyumov-Gerasimenko during the nominal mission

Abstract : The European Space Agency’s Rosetta spacecraft is in close proximity of comet 67P/Churyumov-Gerasimenko for well over a year now. During this time Rosetta followed the comet from almost 3.5 AU through perihelion at 1.25 AU and away from the Sun again. Part of the scientific payload scrutinizing the comet is the ROSINA experiment, the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis. The suite of instruments consists of the Double Focusing Mass Spectrometer DFMS, the Reflectron Time-Of-Flight mass spectrometer RTOF, and the COmet Pressure Sensor COPS. From the combined measurements by ROSINA, the composition and dynamics of the volatiles in the coma of the comet are derived. On 13 August 2015, comet 67P/Churyumov-Gerasimenko reached perihelion, the point along its orbits that is closest to the Sun. Furthermore equinox occurred in May 2015 leading to a change in season – the previous summer hemisphere is now in winter and vice versa. One of the goals of ROSINA is to track the activity of the comet during its apparition and to investigate potential changes in the chemical composition as the spacecraft orbits around the nucleus. In this presentation we will summarize some key findings obtained during the first year and a half of the nominal mission and present first results comparing the pre- and post perihelion neutral gas coma. The goal of these observations is to gather information about the formation and the composition of the comet and ultimately our early Solar System.