The updated 2009 edition of the spectroscopic database GEISA (Gestion et Etude desInformations Spectroscopiques Atmosphe´ riques; Management and Study of AtmosphericSpectroscopic Information) is described in this paper. GEISA is a computer-accessiblesystem comprising three independent sub-databases devoted, respectively, to: lineparameters, infrared and ultraviolet/visible absorption cross-sections, microphysicaland optical properties of atmospheric aerosols. In this edition, 50 molecules are involvedin the line parameters sub-database, including 111 isotopologues, for a total of 3,807,997entries, in the spectral range from 106 to 35,877.031 cm1.The successful performances of the newgeneration of hyperspectral sounders dependultimately on the accuracy to which the spectroscopic parameters of the optically activeatmospheric gases are known, since they constitute an essential input to the forwardradiative transfer models that are used to interpret their observations. Currently, GEISA isinvolved in activities related to the assessment of the capabilities of IASI (InfraredAtmospheric Sounding Interferometer; <a href="http://smsc.cnes.fr/IASI/index.htm" rel="nofollow">http://smsc.cnes.fr/IASI/index.htm</a>) on board theMETOP European satellite through the GEISA/IASI database derived from GEISA. Since theMetop-A (<a href="http://www.eumetsat.int" rel="nofollow">http://www.eumetsat.int</a>) launch (19 October 2006), GEISA is the referencespectroscopic database for the validation of the level-1 IASI data. Also, GEISA is involvedin planetary research, i.e., modeling of Titan’s atmosphere, in the comparison withobservations performed by Voyager, or by ground-based telescopes, and by the instru-ments on board the Cassini–Huygens mission.GEISA, continuously developed and maintained at LMD (Laboratoire de Me´te´orologieDynamique, France) since 1976, is implemented on the IPSL/CNRS (France) ‘‘Ether’’Products and Services Centre WEB site (<a href="http://ether.ipsl.jussieu.fr" rel="nofollow">http://ether.ipsl.jussieu.fr</a>), where all archivedspectroscopic data can be handled through general and user friendly associated manage-ment software facilities.More than 350 researchers are registered for on line use of GEISA.& 2011 Elsevier Ltd. All rights reserved.