Polar, Wind, Geotail Project
&To develop a comprehensive, global understanding of the generation and flow of energy from the Sun through the Earth's space environment (geospace) and to define the cause-and-effect relationships between the physical processes that link different regions of this dynamic environment.& - Alexander and Nishida, 1984
In the 1990s, collaborations between NASA, the European Space Agency (ESA), and the Institute of Space and Astronuatical Science (ISAS) of Japan resulted in the International Solar-Terrestrial Physics (ISTP) Science Initiative. Polar, Wind and Geotail are a part of this initiative, combining resources and scientific communities to obtain coordinated, simultaneous investigations of the Sun-Earth space environment over an extended period of time.
Information provided by http://pwg.gsfc.nasa.gov/project_overview.shtml