| Abbreviation | Definition |
|---|---|
| ACRC | Assured Crew Return Capability |
| ACRIM | Active Cavity Radiometer Irradiance Monitor |
| ACRM | Advanced Crew Resource Management |
| ACRS | Automated Conflict Resolution System |
| ACRV | Assured Crew Return Vehicle |
| ACRV | Astronaut Crew Return Vehicle |
| ACRV | Attitude Controlled Re-entry Vehicle |
| ACRV-X | Assured Crew Return Vehicle - Experimental |
| ACS | Advanced Camera for Surveys (Hubble Space Telescope) |
| ACS | Atmosphere Control System |
| ACS | Attitude Control System |
| ACSM | Attitude Control System Moding |
| ACTA | Asteroid And Comet Tracking Agency |
| ACTS | Advanced Communications Technology Satellite |
| ACTS | Advanced Computational Testing And Simulation |
| ACU | Arm Computer Unit |
| ACU | Arm Control Unit |
| ACU | Attitude Control Unit |
| AD | Active Device |
| AD | Analog to Digital |