| L | Launch |
| L0 | Level 0 |
| L1B, or L1b | Level 1B; Level 1b |
| L1R | Level 1 Requirement |
| L2 | Level 2 |
| L2+ | Level 2 and higher |
| L&EO | Launch and Early Orbit |
| LACP | Link Aggregation Control Protocol |
| LAE | Liquid Apogee Engine |
| LAN | local area network |
| LAP | Legacy Atmospheric Profile |
| LAPSS | Large Area Pulsed Solar Simulation |
| LaRC | Langley Research Center (NASA) |
| LASP | Laboratory for Atmospheric and Space Physics |
| LAT | Lot Acceptance Test |
| LB | Load Balancer |
| LBC | Labor Bid Code |
| LBLRTM | Line-By-Line Radiative Transfer Model |
| LBNL/ALS | Lawrence Berkeley National Laboratory/Advanced Light Source |
| LCC | Launch Commit Criteria |
| LCC | Life Cycle Cost |
| LCC | Load Cycle Count |
| LCCE | Life-Cycle Cost Estimate |
| LCE | Life Cycle Engineering |
| LCFA | Lightning Cluster Filter Algorithm |
| LCL | low cloud layer |
| LCR | Launch Control Room |
| LDALC | Linearizer Drive Amplifier with Automatic Level Control |
| LDAP | Lightweight Directory Access Protocol |
| LDAR | Lightning Detection and Ranging |
| LDCM | Landsat Data Continuity Mission |
| LDM | Logical Data Model |
| LDPC | Low Density Parity Check (Coding Technique) |
| LECO | Line Environmental Compliance and Safety Officer |
| LED | Light Emitting Diode |
| LEGF | Lightning Events Groups and Flashes |
| LEO | Low Earth Orbit |
| LEOP | Launch and Early Orbit Phase |
| LER | Lower Equipment Room |
| LET | Linear Energy Transfer |
| LFU | Least Frequently Used |
| LHCP | Left-Hand Circular Polarization |
| LHP | Loop Heat Pipe |
| Li | Lithium |
| LI | Lifted Index |
| LIDAR | LIght Detection And Ranging |
| LIRD | Level 1 Requirements Document |
| LIS | Lightning Imager Sensor |
| LL | Lessons Learned |
| LLA | Launch Lock Assembly |
| LLI | Limited Life Items |
| LLIL | Limited Life Items List |
| LLIS | Lessons Learned Information System |
| LLS | Linear Least Squares |
| LLWG | Lessons Learned Working Group |
| LM | Lockheed Martin |
| LMA | Lightning Mapping Array |
| LMATC | Lockheed Martin Advanced Technology Center |
| LMC | Line-of-sight Motion Compensation |
| LMS | Lockheed Martin Space |
| LMSAL | Lockheed Martin Solar and Astrophysics Laboratory |
| LMSSC | Lockheed Martin Space Systems Company |
| LMT | Lightning Monitoring Tool |
| LNA | Low Noise Amplifiers |
| LO | Line Office |
| LOA | Letter of Agreement |
| LOC | Line of Code |
| LOC | Loss of Capability |
| LOD | Letter of Delegation |
| LOE | Level Of Effort |
| LOH | Late Onset Harmonics |
| LoM | Life of Mission |
| LOR | Launch and Orbit Raising |
| LOS | line-of-sight |
| LP | Low Power |
| LPD | Launch Planning Date |
| LPLA | NASA Langley Parameterized Longwave Algorithm |
| LPM | Low-voltage Power Module |
| LPT | Limited Performance Test |
| LPW | Layer Precipitable Water |
| LR | launch of GOES R satellite |
| LRC | Local Radiative Center |
| LRD | Launch Readiness Date |
| LRE | Latest Revised Estimate |
| LRF | Line-of-sight Reference Frame |
| LRIT | Low-Rate Information Transfer |
| LRIT | Low Rate Information Transmission Transmission (for GOES-R to be provided by HRIT/EMWIN) |
| LRITT | Low Rate Information Transmission Terminal |
| LRR | Launch Readiness Review |
| LRU | Line Replaceable Unit |
| LS | Launch Segment |
| LS | launch of GOES-S satellite |
| LSA | Land Surface Albedo |
| LSA | Logistics Support Analysis |
| LSAR | Logistics Support Analysis Record |
| LSB | Least significant bit |
| LSE | Land Surface Emissivity |
| LSE | Launch Support Equipment |
| LSIM | Launch Site Integration Manager |
| LSIP | Launch Site Integration Plan |
| LSP | Launch Services Plan |
| LSP | Launch Services Program |
| LSP | Legacy Sounding Products |
| LSSMA | L-S Band Switch Matrix Assembly |
| LSSP | Launch Site Support Plan |
| LST | Land Surface (Skin) Temperature |
| LSTO | Launch Services Task Order |
| LTR | Low Thrust REA (Rocket Engine Assembly) |
| LTWTA | Linearized Traveling Wave Tube Amplifier |
| LUN | Logical Unit Number |
| LUSI | NIST LUnar Spectral Irradiance |
| LUT | local user terminal |
| LUT | look-up table (ancillary data) |
| LV | launch vehicle |
| LVI | Launch Vehicle Interface |
| LVRR | Launch Vehicle Readiness Review |
| LW | longwave |
| LWC | Liquid Water Content |
| LWIR | longwave infrared; long wavelength infrared |
| LWP | Liquid Water Path |
| LZA | Local Zenith Angle |
| LZSS | Level Zero Storage Service (+B12) |