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- Astronomisches Institut der Ruhr-Universität Bochum
- A.M.Obukhov Institute of Atmospheric Physics
- ABB Bomem Inc.
- ABR, Inc. - Environmental Research and Services
- AGROCAMPUS OUEST
- AIRMARAIX
- AIRPARIF - Surveillance de la qualité de l'air en Île-de-France
- AIT Advanced Information Technologies Corporation
- ALCATEL
- ALCATEL SPACE
- APC - Cosmologie
- ARPA Emilia-Romagna, Agenzia Regionale per la Protezione dell’Ambiente
- ARQM Meteorological Service Canada
- ASTRIUM
- ATMOS Sarl
- Aarhus University [Aarhus]
- Abdus Salam International Centre for Theoretical Physics [Trieste]
- Aberystwyth University
- Academy of Athens
- Addis Ababa University
- Agence Spatiale Européenne
- Agencia Estatal de Meteorología
- AgroParisTech
- Air Force Geophysics Laboratory
- Air Force Research Laboratory
- Air Quality Research Division [Toronto]
- Aix Marseille Université
- Alfred Wegener Institute [Potsdam]
- Alfred Wegener Institute for Polar and Marine Research
- Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
- Allied Signal Corporation
- Alma Mater Studiorum Università di Bologna [Bologna]
- Ambiances architecturales et urbaines
- Analytic and Computational Research, Inc. - Earth Sciences
- Analytical Services and Materials
- Analytical Services and Materials Inc.
- Andøya Rocket Range
- Anglo-Australian Observatory
- Applied Marine Physics [Miami]
- Arctic Research Centre of Finnish Meteorological Institute
- Argelander-Institut für Astronomie
- Argentière
- Argonne National Laboratory [Lemont]
- Aristotle University of Thessaloniki
- Armagh Observatory [Armagh]
- Array Systems Computing
- Arrhenius Laboratory
- Association of Universities for Research in Astronomy
- Astrium SAS
- Astrium Satellites
- Astrium [Stevenage]
- Astrium [Toulouse]
- AstroParticule et Cosmologie
- Astronomical Institute Anton Pannekoek
- Astronomical observatory of Odessa National University [Odessa]
- Astronomie et systèmes dynamiques
- Astronomy Unit [London]
- Astrophysics Research Centre [Belfast]
- Astrophysique Interprétation Modélisation
- Atmospheric Chemistry Division [Boulder]
- Atmospheric Chemistry Modelling Support Unit [Cambridge]
- Atmospheric Chemistry and Dynamics Branch [ Greenbelt]
- Atmospheric Physics Laboratory [UCL London]
- Atmospheric Sciences Division [Hampton]
- Atmospheric Systems and Analysis [Westminster]
- Atmospheric and Environmental Research, Inc.
- Atmospheric and Oceanic Sciences Program [Princeton]
- Atmospheric, Oceanic, and Space Science Department, University of Michigan
- Australian Antarctic Division
- Australian Bureau of Meteorology [Melbourne]
- Australian Centre for Astrobiology
- Australian Government
- Australian Government, Department of the Environment and Energy
- Austrian Academy of Sciences
- Avant création Cerema
- Avignon Université