- Aalborg University [Denmark]
- Aalto University
- Aarhus University [Aarhus]
- Abdelhamid Ibn Badis University
- Abdou Moumouni University of Niamey = Université Abdou Moumouni de Niamey
- Abdus Salam International Centre for Theoretical Physics [Trieste]
- Aberystwyth University
- Abteilung für Partikelchemie [Mainz]
- Academia Sinica
- Academia Sinica Institute of Astronomy and Astrophysics
- Académie des sciences [Paris, France]
- Academy of Athens
- Academy of Sciences of the Republic of Tajikistan
- Accra North, Ghana
- Active Space Technologies S.A.
- ADDAIR Sté (France)
- Addis Ababa University
- Administratia Nationala de Meteorologie
- ADNET Systems, Inc.
- Advanced Heliophysics
- Advanced Instrumentation for Ion Nano-Analytics
- Advanced Lithium Energy Storage Systems - ALISTORE-ERI
- Advanced Mechanical and Optical Systems SA
- Advanced Methods for Satellite Positioning Laboratory
- Advanced Radar Research Center [Norman]
- Advanced Research Center for Space Science and Technology [Kanazawa]
- Advanced Space LLC
- Advanced Wireless and Communication Research Center [Tokyo]
- Aeolis Corporation
- Aeolis Research
- AEROCAN Network
- Aerodyne Industries
- Aerodyne Research Inc.
- Aeroport International de Marseille-Provence
- Aeroqual Ltd.
- Aerosol Physics and Environmental Physics [Vienna]
- Aerovironment, Inc.
- AESTER COGNITIO
- AESTER INCOGNITO
- A.F. Ioffe Physical-Technical Institute
- African Centre of Meteorological Applications for Development
- AFRL Space Vehicles Directorate
- Agence d’Écologie Urbaine
- Agence de l'innovation de défense
- Agence de surveillance de la qualité de l’air
- Agence fédérale de contrôle nucléaire
- Agence Française pour la Biodiversité
- Agence nationale de la météorologie du Bénin
- Agence Nationale pour la Gestion des Déchets Radioactifs
- Agence pour la sécurité de la navigation aérienne en Afrique et à Madagascar
- Agence Spatiale Algérienne = Algerian Space Agency
- Agence Spatiale Européenne = European Space Agency
- Agencia Estatal de Meteorología
- Agencia Nacional de Promoción Científica y Tecnológica
- Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile
- Agenzia Nazionale per le nuove Tecnologie, l’energia e lo sviluppo economico sostenibile = Italian National Agency for New Technologies, Energy and Sustainable Economic Development
- Agenzia Regionale per la Protezione dell'Ambiente Valle D'Aosta
- Agenzia Spaziale Italiana
- Agricultural and Food Engineering Department
- Agricultural Research, Education and Extension Organisation
- Agricultural University of Athens
- Agrifood Research and Technology Centre of Aragon
- AGROCAMPUS OUEST
- AgroParisTech
- Agroscope
- Agroscope Reckenholz - Tänikon
- Agrosphere, IBG-3
- Airbus Defence and Space [Les Mureaux]
- Airbus Defence and Space Ltd [Portsmouth]
- Airbus Defence and Space [Taufkirchen]
- Airbus Defence and Space [Toulouse]
- Airbus Defense and Space, Toulouse
- Airbus [France]
- Airbus Group [Germany]
- Airbus Helicopters
- Airbus [United Kingdom]
- AIRES Pty. Ltd.
- Air Force Research Laboratory
- Air Liquide Advanced Technologies [Sassenage]
- Air Liquide [Siège Social]
- AIRPARIF - Surveillance de la qualité de l'air en Île-de-France
- Air Quality and Climate Change Division [Jerusalem]
- Air Quality Processes Research Section
- Air Quality Research Division [Toronto]
- A. I. Voeikov Main Geophysical Observatory
- Aix Marseille Université
- Ajou University
- Akademie der Wissenschaften zu Göttingen
- Akademischer Lehrgang Software Engineering
- Akdeniz University
- Akka Informatique et Systèmes
- AKKA Technologies
- Alaska Climate Research Center
- Alaska Department of Environmental Conservation
- Alberta Environment and Parks
- Alberta Government
- Albert-Ludwigs-Universität Freiburg = University of Freiburg
- Aleut International Association
- Alexandru Ioan Cuza University of Iași = Universitatea Alexandru Ioan Cuza din Iași
- Alfred Wegener Institute for Polar and Marine Research
- Alfred Wegener Institute [Potsdam]
- Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine
- Algorithms and parallel tools for integrated numerical simulations
- Algorithms and Software Architectures for Distributed and HPC Platforms
- Alma Mater Studiorum Università di Bologna = University of Bologna
- Altair Engineering France
- AMDL srl
- American Public University System
- American University of Sharjah
- American University Washington D.C.
- A.M.Obukhov Institute of Atmospheric Physics
- AMOS S.A.
- A. M. Prokhorov General Physics Institute
- AMSAT-Francophone
- AMU Engineering, Inc.
- Analytical Mechanics Associates, Inc.
- Analytic and Computational Research, Inc. - Earth Sciences
- Anglo-Australian Observatory
- Angström Laboratory
- Anhui Institute of Optics and Fine Mechanics
- Antarctic Climate and Ecosystems Cooperative Research Centre
- ANU College of Science [Canberra]
- Anunaki Observatory
- Aosta Valley Regional Environmental Protection Agency
- Aoyama Gakuin University
- APC - Cosmologie
- Appalachian State University
- Applied Physics Laboratory [Seattle]
- Applied Research Associates, Inc.
- Approches Littéraires, Linguistiques et Historiques des Sources
- APS College of Engineering
- ARC Centre of Excellence for Climate System Science
- Architecture et Logiciels pour Systèmes Embarqués sur Puce
- Architectures et Modèles pour l'Interaction - LISN
- Arctic and Antarctic Research Institute
- Arctic Geophysics Research
- Arctic Research Center [Sapporo]
- Arctic Space Centre [Helsinki]
- Ardans SAS
- Arecibo Observatory, National Astronomy and Ionosphere Center
- ARGANS Limited
- Argonne National Laboratory [Lemont]
- ARIA Technologies
- Aristotle University of Thessaloniki
- Arizona State University [Tempe]
- Arkansas Center for Space and Planetary Sciences
- ARL Atmospheric Turbulence and Diffusion Division
- Armagh Observatory and Planetarium
- Armagh Observatory [Armagh]
- Armenian State Pedagogical University
- ARPA-SIM
- Array Systems
- Array Systems Computing
- Array Systems Computing Inc.
- Artenum
- Artenum, Paris
- artenum SARL
- Arthur Amos Noyes Laboratory of Chemical Physics
- Artificial Intelligence Research Center [Tokyo]
- Arts et Métiers Paristech ENSAM Aix-en-Provence
- Aryabhatta Research Institute of Observational Sciences
- Ashikaga Institute of Technology
- Ashima Research
- Asia Center for Air Pollution Research
- Asian School of the Environment
- Asociación Astronómica Astro Henares
- Asociacio n para la Conservacio n y Estudio de Montañas Andinas-Amazo nicas
- ASP 2014
- ASP 2015
- ASP 2016
- ASP 2018
- ASP 2019
- ASP 2023
- ASRC Federal Space and Defense
- Assam University
- Assistance publique - Hôpitaux de Paris (AP-HP)
- Association AstroQueyras
- Association Française d'Astronomie
- Association Française d'Astronomie - Ciel et Espace
- Association of African Universities
- Association of International Research Initiatives for Environmental Studies
- Association of Universities for Research in Astronomy
- Association pour la Surveillance et l'Étude de la Pollution atmosphérique en Alsace
- Association T60, Observatoire Midi-Pyrénées
- Associazione Astrofili Alta Valdera
- Associazione Romana Astrofili
- Asteroid Engineering Laboratory [Kiruna]
- Astéroïdes, comètes, météores et éphémérides
- ASTRIUM
- Astrium GmbH
- Astrium Ltd, Gunnels Wood Road, Stevenage
- Astrium [Portsmouth]
- Astrium [Stevenage]
- Astrium [Toulouse]
- Astrochemistry Laboratory [Greenbelt]
- Astrochimie, Spectroscopie, Théorie, Réactivité, Origine
- Astrogeology Science Center [Flagstaff]
- Astromaterials Research and Exploration Science
- ASTRONIKA Sp. Zo.o.
- Astronomía Espacial y Gestión Óptima de Recursos Astronómicos
- Astronomical Institute Anton Pannekoek
- Astronomical Institute [Bern]
- Astronomical Institute of Charles University
- Astronomical Institute of Romanian Academy
- Astronomical Institute of the Czech Academy of Sciences
- Astronomical Institute of the Slovak Academy of Sciences
- Astronomical Institute [Wroclaw]
- Astronomical Observatory [Poznan]
- Astronomical Research Institute [Ashmore]
- Astronomical Ring for Access to Spectroscopy
- Astronomy Unit [London]
- AstroParticule et Cosmologie
- Astrophysics and Geophysics Institute [Liège]
- Astrophysics Research Centre [Belfast]
- Astrophysics Research Institute [Liverpool]
- Astrophysique Interprétation Modélisation
- ASU School of Earth and Space Exploration
- ATA Aerospace
- Atacama Large Millimeter|submillimeter Array
- ATERMES [Montigny-le-Bretonneux]
- ATMO Hauts de France [Lille]
- Atmosphere
- Atmosphere and Ocean Research Institute [Kashiwa-shi]
- ATMOSPHERE - LATMOS
- Atmospheric and Climate Applications, Inc.
- Atmospheric and Environmental Research, Inc.
- Atmospheric and Oceanic Sciences Program [Princeton]
- Atmospheric Chemistry and Dynamics Laboratory [ Greenbelt]
- Atmospheric Chemistry Department [MPIC]
- Atmospheric Chemistry Division [Boulder]
- Atmospheric Chemistry Observations and Modeling Laboratory
- Atmospheric Chemistry Services [UK]
- Atmospheric Research Centre of Eastern Finland
- Atmospheric Sciences and Global Change Division [Richland]
- Atmospheric Sciences Research Center
- AtmoSud, Regional Agency for Air Quality Monitoring
- Atomic and Molecular Physics Laboratories
- Atos
- ATOS Origin
- Auburn University
- Auckland Council
- Auden Technology and Management Academy
- Aurora Technology BV
- Austral, Boréal et Carbone
- Australian Antarctic Division
- Australian Bureau of Meteorology [Melbourne]
- Australian Bureau of Meteorology Training Centre
- Australian Government
- Australian Government, Department of the Environment and Energy
- Australian Institute of Marine Science
- Australian Institute of Marine Science [Townsville]
- Australian National University
- Australian Research Council [Canberra]
- Austrian Academy of Sciences
- Austrian Research Centre-Seibersdorf Research GmbH
- Avant création Cerema
- Avignon Université
- A.V. Topchiev Institute of Petrochemical Synthesis
- AXA France
- AXA Group Risk Management Department [Paris]