International Cooperation With Japan in the International Solar-Terrestrial Physics/GGS Program

The origin of the Geotail Program and the collaboration with Japan traces back to the Origin of Plasmas in the Earth's Neighborhood (OPEN) Program, a fleet of four spacecraft studied at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) in the early 1980s to conduct multipoint, coordinated measurements in the Earth's magnetosphere and the interplanetary medium. The OPEN program was the natural evolution of the early discovery missions, which although finding many new regions and plasmaphysical phenomena in the magnetosphere had problems separating cause-and effect relationships and resolving space-time ambiguities. The primary scientific objective was the coordinated study of the flow of energy, mass, and momentum from the Sun through the interplanetary medium and its eventual deposition in the Earth's atmosphere. This objective was to be achieved in a quantitative manner and to that extent theory, models, and ground-based observations were incorporated for the first time as an integral part of the project baseline. An ambitious ground system, capable of processing and visualizing the vast amounts of data generated by these spacecraft, was also conceived and incorporated in the OPEN concept.