Mass spectrometry of newly ionized cometary gas by plasma instruments onboard the Giotto and Vega space probes

The combined capabilities of instrumentation on board the Giotto and Venera-Halley (VH) spacecraft are shown to furnish sufficient data for analyzing the main components of the cometary coma and thus gain insight into the parent molecules. It is expected that the ionized dust will (collectively) reside in the solar wind for intervals exceeding the period of cyclotron rotation. Cold plasma measurements will be made by the Plazmag-1 instrument on VH and by three instruments on the Giotto spacecraft. The narrow angles of acceptance of the instruments is shown to allow calculations of the rate of disappearance of newly formed ions and their identities. Ions with mass numbers below 25 will be characterized, as will features of the solar wind-coma interaction.