Ulysses Status Report - November 2006
Operations and Archive
During the reporting period, science operations have been conducted according to the revised payload power-sharing plan. Largely as a result of the gradually improving thermal situation as Ulysses gets closer to the Sun, several instruments not in the core payload category have been able to acquire data for short periods of time (typically 1 month). These include the gamma-ray burst experiment and the solar wind electron sensor.
Rather than focusing on a new science result from the mission, this report highlights the many contributions to Ulysses science made by Johannes Geiss. As well as being one of the fathers of the mission (and one of its longest-serving PIs), Geiss is a world leader and foremost expert on measurements and interpretation of composition of matter that reveals the history, present state, and future of astronomical objects. Johannes Geiss was first to measure the composition of the noble gases in the solar wind when, in the late 1960s, he flew a foil experiment to collect solar wind ions on the five Apollo missions to the Moon. In recent years, together with colleagues on the Ulysses/SWICS team, he has determined the isotopic and elemental composition of the solar wind under all solar wind conditions and at all helio-latitudes.
Many of the fundamental contributions to our knowledge of the heliosphere to have been made using Ulysses/SWICS have come from the study of pickup ions. Johannes Geiss and colleagues discovered and characterized pickup ions of interstellar origin (in particular, heavy ions and 3He) from which the composition of the neutral gas of the Local Interstellar Cloud surrounding the heliosphere could be determined. They also discovered a so-called "Inner Source" of pickup ions. These ions are thought to originate from solar wind that is implanted in dust grains near the Sun. The particles are subsequently released as neutrals, and become ionized once again. Geiss' quest to measure and understand the composition of matter is not limited to the solar wind and pickup ions. He has also played a key role both in the in-situ measurements of molecular ions in comets and the interpretation of these data, and in the study of the composition of plasmas in the magnetospheres of Earth and Jupiter.
This report was prepared on 13 October 2006, and presented to SPC on 7-8 November 2006.