Remote sensing of the ionosphere by space-based GNSS observations

The GNSS-based radio occultation measurements establish the foundation of a novel remote sensing technique capable of reliably deducing the electron density distribution in the entire ionosphere from the GNSS satellite heights down to the bottom ionospheric heights. The ionospheric radio occultation measurements have been carried out onboard the German low orbiter CHAMP since 11 April 2001. Presented and discussed here are some important results obtained during this highly successful mission.