| Abbreviation | Definition |
|---|---|
| IOCU | Input/Output Control Unit |
| IOE | Input/Output Error Log Table |
| IOF | Initial Operational Flight |
| IOM | Input/Output Module |
| IOM | Institute Of Medicine |
| IONS | Heavy Nucleii |
| IONS | Studies of the Ionization States of Solar and Galactic Cosmic Ray |
| IOP | In-Orbit Plane |
| IOP | Input/Output Port |
| IOP | Input/Output Processor |
| IOP | Integrated Operation Plan |
| IOP | Internal Operating Plan |
| IOPL | Integrated Open Problem List |
| IOQE | Input/Output Queue Element |
| IOS | Indian Ocean Ship, Spaceflight Tracking Data network station |
| IOS | Indian Ocean Station |
| IOS | Input/Output Supervision |
| IOS | Instructor Operator Station |
| IOSC | Integrated Operations Support Center |
| IOSS | Integrated Orbital Service System |