| Term | Definition / Meaning / Stand for |
| PLATO |
PLAnetary Transits and Oscillations of stars |
| PSS |
Palomar Sky Survey |
| PAN |
Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) |
| PS1 |
Pan-STARRS1 |
| PTO |
Parallax Tracking Observatory |
| PAV |
Parallax and Velocity |
| P |
Parallax |
| PLUTO |
Parallelized Local Update with Timestep Ordering |
| PKS |
Parkes (Radio Telescope Catalog) |
| PKS |
Parkes Catalogue of Radio Sources |
| PKS |
Parkes Observatory Source |
| PEC |
Period Error Correction |
| PLR |
Period-Luminosity Relation |
| PANIC |
Persson's Auxiliary Nasmyth Infrared Camera |
| PAB |
Phase Angle Bisector |
| PRIMA |
Phase-Referenced Imaging and Micro-arcsecond Astrometry |
| PACS |
Photodetector Array Camera and Spectrometer |
| PD |
Photodetector |
| PEL |
Photographic Emulsion Layer |
| PHT |
Photometer |
| PEL |
Photometric Event List |
| PPT |
Photometric Period Transit |
| PZ |
Photometric Redshift |
| PZT |
Photometric Zenith Tube |
| PHO |
Photometry |
| PDR |
Photon Dominated Region |
| PDR |
Photon-Dominated Region |
| PION |
Physics of Ions |
| PPP |
Pixel Phase Processor |
| PLCK |
Planck Catalogue |
| PLA |
Planck Collaboration Archive |
| PAC |
Planetary Astronomy Center |
| PDC |
Planetary Data Center |
| PDT |
Planetary Dynamics Team |
| PE |
Planetary Ephemeris |
| PEA |
Planetary Exploration Archive |
| PIA |
Planetary Image Atlas |
| PISCES |
Planetary Imaging Concept Testbed Using a Silver Chalcogenide Experiment |
| PIM |
Planetary Imaging Model |
| PIE |
Planetary Impact Event |
| PIR |
Planetary Infrared Radiometer |
| PMO |
Planetary Mission Operations |
| PNB |
Planetary Nebula Binary |
| PNC |
Planetary Nebula Cluster |
| PLB |
Planetary Nebula Luminosity Function |
| PNM |
Planetary Nebula Morphology |
| PNS |
Planetary Nebula Spectrum |
| PN |
Planetary Nebula |
| PPP |
Planetary Parallax Parameter |
| PST |
Planetary Science Team |
| PSS |
Planetary Survey Satellite |
| PWS |
Planetary Wave Spectrometer |
| PVM |
Plasma Velocity Model |
| PEPSSI |
Pluto Energetic Particle Spectrometer Science Investigation |
| PRF |
Point Response Function |
| POT |
Pointing Observation Tool |
| PAM |
Polar Alignment Mode |
| PMC |
Polar Mesospheric Cloud |
| PMA |
Polar Motion Accuracy |
| PZO |
Polar Zone Observatory |
| PZO |
Polarization Zero Offset |
| PCG |
Poor Cluster of Galaxies |
| POP |
Population (stellar population) |
| POCS |
Portable Observatory Control System |
| PAS |
Position Angle of Source |
| PVD |
Position-Velocity Diagram |
| PPM |
Positions and Proper Motions (catalogue) |
| PAP |
Post-AGB (Post-Asymptotic Giant Branch) |
| POT |
Potential Energy |
| PBD |
Pre-Big Bang |