| Acronym | Meaning |
 | OSP | Operations Support Plan |
 | OSR | Operations Support Room |
 | OSS | OEX SuPport System |
 | OSS | Office Of Space Science |
 | OSS | OPtics Subsystems |
 | OSS | Orbiting Space Station |
 | OSSA | Office Of Space Science And Applications |
 | OSSRH | Orbiter Subsystem(s) Requirements Handbook |
 | OST | Operations Support Team (GSFC) |
 | OST | Orbiter SuPport Trolley |
 | OSTA | Office Of Space And Terrestrial Application(s) |
 | OSTDS | Office Of Space Tracking And Data Systems |
 | OSTO | Office Of Space Transportation Operations |
 | OSTP | Orbiting System Test Plan |
 | OSTS | Office Of Space Transportation Systems |
 | OT | Operating Time |
 | OT | Operational Instrumentation MDM-Tank |
 | OT | Operational Test |
 | OT | Operational Trajectory |
 | OT | Optical Tracker |
 | OT | Out Temperature |
 | OT | Overti Me |
 | OT&E | Operational Test And Evaluation |
 | OTA | Optical Telescope Assembly |
 | OTB | Orbiting Tanker Base |
 | OTBD | Outboard |
 | OTC | Orbiter Test Conductor |
 | OTD | Operational Technical Documentation |
 | OTD | Orbiter Test Director |
 | OTDA | Office Of Tracking And Data Acquisition (now OSTDS) |
 | OTEMP | Overtemperature |
 | OTH | Over-the-Horizon (.Radar) |
 | OTK | Oxidizer Tank |
 | OTL | Ordnance Test Laboratory |
 | OTLC | Orbiter Timeline Constraints |
 | OTO | One-Time-Only |
 | OTOS | Orbit-to-Orbit Stage |
 | OTP | OPerational Test Procedure |
 | OTP | Operations Test Plan |
 | OTP | Operations Turnaround Plan |
 | OTR | Operating Time Record |
 | OTR | Outer |
 | OTS | Off-the-Shelf |
 | OTS | Orbiter Test Conductor |
 | OTT | Optional Team Targeting |
 | OTV | Operational Television |
 | OTV | Orbital Transfer Vehicle |
 | OTV | Orbiter Transfer Vehicle |
 | OTY | Quantity |
 | OUI | Quito |