| Abbreviation | Definition |
|---|---|
| ISI | Instrument/Spacecraft Interface |
| ISI | Instrumentation Support Instruction |
| ISIL | Interim Support Items List |
| ISIM | Integrated Science Instrument Module |
| ISIS | Integrated Science Instrument System |
| ISIS | International Satellite for Ionospheric Studies |
| ISL | Inertial Systems Laboratory |
| ISL/LAR | Integrated Logistics System and Logistics Assessment Review |
| ISLM | Integration Shop/Lab Manager |
| ISN | Intelligent Sensor Network |
| ISN | Inter-Set Network |
| ISO | Imaging Spectrometric Observatory |
| ISO | Information Systems Office |
| ISO | Infrared Space Observatory |
| ISOC | Institutional Safety Office Contact |
| ISOL | ISOLate |
| ISP | Initial Specific Impulse |
| ISP | Instrumentation Support Plan |
| ISPG | Institutional Support Planning Group |
| ISPM | International Solar Polar Mission |