| Abbreviation | Definition |
|---|---|
| APTU | Auxiliary Power and Thrust Unit |
| AQS | Advanced Quality Settings |
| AQS | Air Quality System |
| AR | Atmosphere Revitalization |
| ARC | Ames Research Center |
| ARCADE | Absolute Radiometer for Cosmology Astrophysics and Diffuse Emission |
| ARCU | American-to-Russian Converter Unit |
| ARED | Advanced Resistive Exercise Device |
| ARIA | Advanced Ranging and Instrumentation Aircraft |
| ARIA | Apollo Range Instrumented Aircraft |
| ARIS | Active Rack Isolation System |
| ARISS | Amateur Radio on the International Space Station |
| ARM | Accident Report Meeting |
| ARO | Automatic Reconfiguration Order |
| ARP | Aerospace Recommended Practice |
| ARP | Automated Release Processing |
| ARQ | Authentication Request |
| ARS | Air Revitalization System |
| ARS | Air Roll Spin |
| ARS | Archive and Retrieval Sub-system |