ICON is focusing on a region of space between 60 and 300 miles above the Earth’s surface. This region is made up of a mix of atoms and molecules. Some of these are similar to the atoms and molecules we find in air near the surface; we call these “neutral” because they have no electric charge. However, some of these atoms and molecules have their electrons stripped away by ultraviolet radiation from the Sun. Since a is negative charge has been removed from these particles, they have excess positive charge, and therefore are no longer neutral. We call these ions. The region of space where these ions and free electrons coexist with the remaining neutrals is called the ionosphere - literally a sphere of ions.