| LAGEOS | Laser Geodynamics Satellite | - | Atmospheric Research Center |
| LANL | Los Alamos National Laboratory | - | Atmospheric Research Center |
| LARC | Langley Research Center | - | Atmospheric Research Center |
| LASCO | Large Angle Spectrometric Coronograph | - | Atmospheric Research Center |
| LC | Launch Complex | - | Atmospheric Research Center |
| LDEF | Long Duration Exposure Facility | - | Atmospheric Research Center |
| LEDA | On-line Earthnet Data Access | - | Atmospheric Research Center |
| LEM | Lunar Excursion Module | - | Atmospheric Research Center |
| LEO | Low Earth Orbit | - | Atmospheric Research Center |
| LERC | Lewis Research Center | - | Atmospheric Research Center |
| LEST | Large Earth-based Solar Telescope | - | Atmospheric Research Center |
| LFC | Large Format Camera | - | Atmospheric Research Center |
| LGA | Low Gain Antenna | - | Atmospheric Research Center |
| LGM | Little Green Men | - | Atmospheric Research Center |
| LH | Liquid Hydrogen | - | Atmospheric Research Center |
| LHA | Local Hour Angle | - | Atmospheric Research Center |
| LIS | Lightning Imaging Sensor | - | Atmospheric Research Center |
| LLNL | Lawrence-Livermore National Laboratory | - | Atmospheric Research Center |
| LM | Lunar Module | - | Atmospheric Research Center |
| LMC | Large Magellanic Cloud | - | Atmospheric Research Center |
| LN2 | Liquid Nitrogen | - | Atmospheric Research Center |
| LOX | Liquid OXygen | - | Atmospheric Research Center |
| LPO | La Palma Observatory | - | Atmospheric Research Center |
| LPV | Long Period Variable | - | Atmospheric Research Center |
| LRB | Liquid Rocket Booster | - | Atmospheric Research Center |
| LRSI | Low-temperature Reusable Surface Insulation | - | Atmospheric Research Center |
| LSR | Local Standard Of Rest | - | Atmospheric Research Center |
| LST | Local Sidereal Time | - | Atmospheric Research Center |
| LTP | Lunar Transient Phenomenon | - | Atmospheric Research Center |
| LY | Light Year (usu. Ly) | - | Atmospheric Research Center |
