| Acronym | Meaning |
| HW | Hotwire |
| EFCS | Earth Fixed Coordinate System |
| EL | MECH Electromechanical |
| GEOSYNCHRON | Geosynchronous Operational Environmental Satellite |
| DP/DT | Delta Pressure/Delta Time |
| PER | Preliminary Engineering Report |
| FMR | Field Modification Request |
| MO | Master Oscillator |
| FREO | DIV FrequencY Divider |
| SYNCOM | Synchronous Communication Satellite (Hughes) |