The Deep Space 1 encounter with comet 19P/Borrelly Original Research Article

The Deep Space 1 Mission successfully encountered comet 19P/Borrelly on 22 September 2001, returning a wealth of images and in situ plasma measurements. To enhance the scientific return of the mission, it is desired to gain knowledge of basic properties of the cometary environment through the interpretation and analysis of the spacecraft data. For this purpose, a coma model for 19P/Borrelly during encounter is presented that consistently represents the cometary environment from the nucleus surface to the solar wind interaction region with detailed chemistry. Neutral gas and plasma dynamics and spatial distributions of various cometary species from the model are presented for interpreting in situ plasma measurements obtained during the encounter. Whereas several features of the plasma environment were well modeled, such as, the standoff distance of the bow shock and the ion velocity profile; the abundances of water-group ions around closest approach are not easily understood in terms of the coma chemistry model. Further data analysis and interpretation is needed.