Building on its heritage in planetary science, remote sensing of the Earth s at- sphere and ionosphere with occultation methods has undergone remarkable dev- opments since the rst GPS/Met proof of concept mission in 1995. Signals of Global Navigation Satellite Systems (GNSS) satellites are exploited by radio occ- tation while natural signal sources are used in solar, lunar, and stellar occultations. A range of atmospheric variables is provided reaching from fundamental atmospheric parameters such as density, pressure, and temperature to water vapor, ozone, and othertracegasspecies....