| GAS | Get-Away Special | - | Atmospheric Research Center |
| GBT | Green Bank Telescope | - | Atmospheric Research Center |
| GC | Galactic Center | - | Atmospheric Research Center |
| GC | Globular Cluster | - | Atmospheric Research Center |
| GCVS | General Catalog Of Variable Stars | - | Atmospheric Research Center |
| GDCLS | General Dynamics Commercial Launch Services | - | Atmospheric Research Center |
| GDS | Great Dark Spot | - | Atmospheric Research Center |
| GEM | Giotto Extended Mission | - | Atmospheric Research Center |
| GEM | Graphite Epoxy Motor | - | Atmospheric Research Center |
| GEO | Geosynchronous Earth Orbit | - | Atmospheric Research Center |
| GEODSS | Ground-based Electro-optical Deep-space Surveillance System | - | Atmospheric Research Center |
| GGM | Goskogidromet/Gidromettsentr | - | Atmospheric Research Center |
| GHA | Greenwich Hour Angle | - | Atmospheric Research Center |
| GHRS | Goddard High Resolution Spectrograph | - | Atmospheric Research Center |
| GIF | Graphics Interchange Format | - | Atmospheric Research Center |
| GISS | Goddard Institute For Space Studies | - | Atmospheric Research Center |
| GLOMR | Global Low-Orbiting Message Relay | - | Atmospheric Research Center |
| GMC | Giant Molecular Cloud | - | Atmospheric Research Center |
| GMRT | Giant Meter-wave Radio Telescope | - | Atmospheric Research Center |
| GMS | Geostationary Meterological Satellite | - | Atmospheric Research Center |
| GMT | Greenwich Mean Time | - | Atmospheric Research Center |
| GNC | Guidance | - | Atmospheric Research Center |
| GOES | Geostationary Orbiting Environmental Satellite | - | Atmospheric Research Center |
| GOMOS | Global Ozone Monitoring By Occultation Of Stars | - | Atmospheric Research Center |
| GOMR | Global Ozone Monitoring Radiometer | - | Atmospheric Research Center |
| GOSAMR | Gelation Of Soils: Applied Microgravity Research | - | Atmospheric Research Center |
| GOX | Gaseous OXygen | - | Atmospheric Research Center |
| GPC | General Purpose Computer | - | Atmospheric Research Center |
| GPPF | Gravitational Plant Physiology Facility | - | Atmospheric Research Center |
| GPS | Global Positioning System | - | Atmospheric Research Center |
| GR | General Relativity | - | Atmospheric Research Center |
| GRO | Gamma Ray Observatory | - | Atmospheric Research Center |
| GRS | Gamma Ray Spectrometer | - | Atmospheric Research Center |
| GRS | Great Red Spot | - | Atmospheric Research Center |
| GRTLS | Glide RTLS | - | Atmospheric Research Center |
| GRU | Glavnoye Razvedivatel'noye Upravileniye | - | Atmospheric Research Center |
| GSC | Guide Star Catalog | - | Atmospheric Research Center |
| GSFC | Goddard Space Flight Center | - | Atmospheric Research Center |
| GSO | GeoSynchronous Earth Orbit | - | Atmospheric Research Center |
| GST | Greenwich Sidereal Time | - | Atmospheric Research Center |
| GTO | Geostationary Transfer Orbit | - | Atmospheric Research Center |
| GUGK | Glavnoye Upravileniye Geodesii I Kartografii | - | Atmospheric Research Center |
