The exosphere was the outermost layer of a planet's atmosphere. Orbital skydiving was done from exospheric altitudes. (VOY: "Extreme Risk")
On stardate 43779.3, the USS Enterprise-D was preparing exospheric charts of the Hayashi system, an essential step towards colonization, before it was intercepted by the USS Hood. (TNG: "Tin Man")
| Structure and layers of an atmosphere |
|---|
| Planetary: troposphere • stratosphere • thermosphere • exosphere ozone layer • ionosphere (D region • E region) • magnetosphere • mesosphere |
| Solar: photosphere • chromosphere • corona |