Robotic Missions in Sun-Earth Space - International Solar-terrestrial Physics (istp) Program

During the 1990s NASA teamed with the European and Japanese space agencies in a project known as the International Solar-Terrestrial Physics (ISTP) Science Initiative. The purpose of the ISTP project is to combine international resources to conduct long-term investigations of the Sun-Earth space environment. The program includes both ground-based studies and space missions. The space activities fall into two categories: terrestrial (Earth-directed) and solar (Sun-directed).

Terrestrial space missions rely on satellites in Earth orbit that gather data about the sun's effects on the planet. This effort is supported by two other U.S. federal agencies—the National Oceanic and Atmospheric Administration (NOAA) and the Department of Energy's Los Alamos National Laboratory (LANL).

As of March 2004 ISTP's solar space missions are ongoing. They are conducted by spacecraft called Cluster, Geotail, Polar, SOHO, and Wind. All but SOHO and Wind are kept in Earth orbit. SOHO and Wind are positioned a million miles from Earth to get a better look at the Sun.