| Abbreviation | Definition |
|---|---|
| RTC | Researching The Cosmos |
| RTLT | Round Trip Light Time |
| RTPW | Rapid True Polar Wander |
| RU | Radius of Uranus |
| RV | Radius of Venus |
| SAAA | San Antonio Astronomical Association |
| SAAA | Shoreline Amateur Astronomical Association |
| SAAO | South African Astronomical Observatory |
| SAC | Saguaro Astronomy Club |
| SAGAS | Southern Area Group of Astronomical Societies |
| SALT | South African Large Telescope |
| SALT | Southern African Large Telescope |
| SAM | Sample Analysis of Mars |
| SAM | Super Active Matter |
| SANSA | South African National Space Agency |
| SAO | Smithsonian Astrophysical Observatory |
| SAO | Swinburne Astronomy Online |
| SAPS | Sub Auroral Polarization Streams |
| SAQG | Singapore Aerospace Quality Group |
| SAR | Synthetic Aperture Radar |