ISEE-3: An old friend visits Earth

From 1978 to 1984, the satellite was the first to orbit a point called the Lagrangian 1 (L1), which lies between Earth and the sun, where the solar wind rushes by on its way to collide with the outskirts of the giant magnetic bubble surrounding Earth, called the magnetosphere. Monitoring that wind helped scientists better understand the interconnected sun-Earth system, which at its most turbulent can affect satellites around Earth.