ACE (Advanced Composition Explorer)
ACME (Advanced Combustion via Microgravity Experiments)
ACRIMSAT (Active Cavity Irradiance Monitor Satellite)
ACS3 (Advanced Composite Solar Sail System)
ACT-America (Atmospheric Carbon and Transport – America)
ADEOS / Midori (Advanced Earth Observing Satellite)
AIM (Aeronomy of Ice in the Mesosphere)
AirMOSS (Airborne Microwave Observatory of Subcanopy and Subsurface)
ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites)
ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey)
ASCA (Advanced Satellite for Cosmology and Astrophysics)
ATLAS (Atmospheric Laboratory of Applications and Science)
ATS (Applications Technology Satellite)
ATTREX (Airborne Tropical TRopopause Experiment)