Geos satellite and planet Earth, 1960s.
© National Aeronautics & Space Administration / Science & Society
This drawing shows the Geos satellite in relation to the magnetosphere of earth. The magnetosphere is the volume of space, surrounding a planet, controlled by the planet's magnetic field, and acting as a magnetic shell. The Geos satellite was part of the US Explorer programme, a series of low-cost satellites devoted to specific scientific objectives. The Geos satellite series was used for geodesy, the study of the Earth's shape.