| Abbreviation | Definition |
|---|---|
| PSI | Planetary Science Institute |
| PSLV | Polar Satellite Launch Vehicle |
| PSR | Pulsating Source of Radiation |
| PST | Personal Solar Telescope |
| PTF | Palomar Transient Factory |
| PTST | Planetary Transit Study Telescope |
| PVAO | Platte Valley Astronomical Observers |
| PX | Planet Xtraterrestrial |
| QBSA | Quarterly Bulletin on Solar Activity |
| QHO | Quail Hollow Observatory |
| QPP | Quasi-Periodic Oscillation |
| QSO | Quasi-Stellar Object |
| QZ | Quasi Zenith |
| R | Ray |
| R&R | Reproducibility And Repeatability |
| RAA | Relative Azimuth Angle |
| RAG | Radio Astronomy Group |
| RAL | Radio Astronomy Lab |
| RAL | Radio Astronomy Laboratory |
| RAMBO | Robust associations of massive baryonic objects |