| Abbreviation | Definition |
|---|---|
| APT | Automatic Photometric Telescope |
| AQR | Aquarius |
| ARAA | Annual Review of Astronomy and Astrophysics |
| ArAS | Armenian Astronomical Society |
| ARAS | Astronomical Ring for Access to Spectroscopy |
| ARGUS | Astronomical Research Group Under Stars |
| ARN | Astronomical Research Network |
| ARO | Algonquin Radio Observatory |
| ARO | Arizona Radio Observatory |
| AS | Astronomical Society |
| ASAS | All Sky Automated Survey |
| ASBD | Astronomical Surveys and Big Data |
| ASCA | Advanced Satellite For Cosmology And Astronomy |
| ASCH | Alien Societies Culture And History |
| ASKAP | Australian Square Kilometre Array Pathfinder |
| ASKC | Astronomical Society of Kansas City |
| ASLV | Augumented Satellite Launch Vehicle |
| ASP | Astronomical Society of the Pacific |
| AST | Apparent Solar Time |
| ASTAC | Astronomy Supercomputer Time Allocation Committee |