New Horizons in Occultation Research

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. Theutilityforatmosphereandclimatearisesfromtheunique properties of self-calibration high accuracy and vertical resolution global coverage and (if using radio signals) all-weather capability. Occultations have become a va- able data source for atmospheric physics and chemistry operational meteorology climate research as well as for space weather and planetary science. The 3rd International Workshop on Occultations for Probing Atmosphere and Climate (OPAC-3) was held September 17–21 2007 in Graz Austria. OPAC-3 aimed at providing a casual forum and stimulating atmosphere for scienti c disc- sion co-operation initiatives and mutual learning and support amongst members of alldifferentoccultationcommunities. Theworkshopwasattendedby40participants from 14 different countries who actively contributed to a scienti c programme of high quality and to an excellent workshop atmosphere. The programme included 6 invited keynote presentations and 16 invited pres- tations complemented by about 20 contributed ones including 8 posters.