| Abbreviation | Definition |
|---|---|
| LTM | Like The Moon |
| LTSA | Long-Term Space Astrophysics |
| LUNNO | Lunar Upper Navigation Nacelle Orb |
| LV | Lunette Verte |
| LWP | Long Wavelength Primary |
| LWR | Long Wavelength Redundant |
| LWS | Long-Wave Spectrograph |
| M18 | Messier 18 |
| MACHO | Massive Astronomical Compact Halo Object |
| MACO | Mars Atmospheric Constellation Observatory |
| MACRO | Monopole Astrophysics and Cosmic Ray Observatory |
| MAHLI | Mars Hand Lens Imager |
| MARS | Mountain Astronomical Research Section |
| MAST | Multimission Archive at Space Telescope |
| MCSA | Mir Cooperative Solar Array |
| MD | Matter Dominated |
| MER | Mars Exploration Rover |
| METI | Messaging Extraterrestrial Intelligence |
| MFP | Magnetic Field Perturbation |
| MG | Meteor Garden |