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    Terms beginning with L

    96 terms from the estate's acronym catalogue.

    L-band
    Radio frequency band spanning 1-2 GHz. Used for GNSS signals, maritime/aeronautical SATCOM, and SAR imaging of forested terrain due to foliage penetration.
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    L/D — Lift-to-Drag Ratio
    Aerodynamic efficiency; the ratio of lift to drag at a given condition.
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    LACP — Link Aggregation Control Protocol
    A protocol that bundles multiple physical links into one logical high-bandwidth link.
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    LADAR — Laser Detection and Ranging
    A laser radar that measures range and forms imagery from returned laser light, often used interchangeably with lidar.
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    Lagrange Points
    Five equilibrium positions (L1-L5) in a two-body system where a small object maintains stable position relative to both bodies. L1, L2, L3 unstable; L4, L5 stable.
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    Lambert Problem
    Given two position vectors and a time of flight, determine the orbit connecting them. Fundamental to interplanetary trajectory design and rendezvous mission planning.
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    LAMPS — Light Airborne Multi-Purpose System
    The ship-based helicopter system extending a warship’s ASW and ASUW sensor and weapon reach.
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    LAN — Local Area Network
    A network connecting devices within a limited area such as a building or campus.
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    Lanchester Equations
    Frederick Lanchester's 1916 attrition models. Linear law (ancient combat): casualties scale linearly with opposing force. Square law (modern aimed-fire combat): casualties scale with the square. Foundation of force-ratio analysis and combat simulation.
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    Lanchester Model
    Mathematical attrition models for combat simulation. Linear law models ancient warfare; square law models modern aimed-fire combat where firepower advantage compounds nonlinearly.
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    LANDCOM — Allied Land Command
    The NATO command responsible for the readiness, standardization, and interoperability of Alliance land forces.
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    LargeSat — Large Satellite
    A satellite over ~1 000 kg wet mass — the traditional bus class for GEO comsats, NRO ISR platforms, and flagship science missions (JWST, Hubble). Contrasts with the SmallSat / NewSpace class. Often custom-built rather than series-produced.
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    Laser Designator
    A device that illuminates a target with a coded laser pulse train for a laser-guided weapon to home on. Can be hand-held, vehicle-mounted, or carried on a targeting pod.
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    Lattice Cryptography
    Cryptographic constructions whose security reduces to hard problems on mathematical lattices (LWE, SIS, Ring-LWE). Underpins most post-quantum standards including Kyber and Dilithium. Favoured for efficiency and broad applicability (KEM, signatures, FHE).
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    Launch Window
    The discrete or continuous time interval during which a launch can achieve mission requirements — orbital plane alignment, ground track, lighting, range safety. ISS rendezvous windows are ~5 minutes; Mars opportunities open every ~26 months.
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    LAWS — Lethal Autonomous Weapon Systems
    Weapons that can select and engage targets without human intervention in the lethal decision. Subject of the UN CCW Group of Governmental Experts negotiations; definitions and regulation remain contested.
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    Layered Defence
    A defence-in-depth approach using multiple sequential or concentric defensive layers, each independently capable of degrading a threat. Air defence: long-range Patriot → medium-range NASAMS → short-range SHORAD → terminal C-RAM.
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    LC50 — Lethal Concentration 50%
    The airborne concentration of a substance expected to kill half of an exposed population.
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    LCAC — Landing Craft, Air Cushion
    A high-speed hovercraft that carries vehicles and cargo from ship to beach over the surf zone.
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    LCC — Amphibious Command Ship
    A command-and-control flagship providing facilities for amphibious force commanders and staff.
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    LCL — Latching Current Limiter
    A protective switch that limits and latches off overcurrent on a spacecraft power line.
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    LCM — Landing Craft, Mechanized
    A small landing craft designed to carry vehicles and cargo directly onto a beach.
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    LCS — Littoral Combat Ship
    A fast, modular surface combatant designed to operate in near-shore littoral environments.
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    LCU — Landing Craft, Utility
    A displacement landing craft used to move vehicles, cargo and troops from ship to shore.
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    LD — Line of Departure
    A line designated to coordinate the departure of attacking units at a specified time.
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    LDA — Landing Distance Available
    The length of runway declared available and suitable for the ground run of a landing aircraft.
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    LDPC — Low Density Parity Check code
    A powerful error-correcting code used in modern satellite links to approach channel capacity.
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    LDUUV — Large Displacement Unmanned Underwater Vehicle
    A large autonomous submersible for long-endurance intelligence and undersea missions.
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    LEO — Low Earth Orbit
    Orbits with altitude between approximately 200 km and 2,000 km. Characterized by short orbital periods (~90 min), low latency, but limited coverage per satellite.
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    LEO Broadband Constellation
    Large satellite constellations in LEO (e.g., Starlink, OneWeb, Kuiper) providing global broadband internet with low latency (~20-40 ms). Require thousands of satellites.
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    LEOP — Launch and Early Orbit Phase
    The critical first days of spacecraft operations after separation from the launch vehicle. Covers solar array deployment, attitude acquisition, orbit raising, and initial subsystem checkout. Highest risk period of the mission.
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    LEP — Linear Error Probable
    The vertical or one-dimensional error magnitude within which half of measurements are expected to fall.
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    Lessons Learned
    Documented knowledge gained from project / mission experience that improves future performance. Effective only when captured in a searchable repository, indexed by context, and referenced during planning of new activities.
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    LET — Linear Energy Transfer
    The energy deposited per unit path length by a charged particle traversing a material (MeV-cm2/mg). Determines the severity of single event effects — higher LET means more ionisation and greater SEU/SEL probability.
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    Levels of Autonomy — Levels of Autonomy (LOA)
    A scale describing how much decision-making authority is delegated from operator to machine. Common scales include Sheridan's 10-level scale and ALFUS. Higher LOA reduces operator workload but raises trust, verification, and accountability challenges.
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    LF — Low Frequency
    The radio band from 30 to 300 kHz, used for navigation beacons and long-wave broadcast.
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    LFA — Low Frequency Active
    A powerful low-frequency active sonar used for long-range detection of quiet submarines.
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    LFM — Linear Frequency Modulation / Chirp
    A waveform whose instantaneous frequency varies linearly with time. Used in pulse-compression radar to achieve long-range detection with short effective pulses via matched-filter processing.
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    LGB — Laser-Guided Bomb
    A free-fall bomb fitted with a laser seeker and control fins that homes on reflections from a laser-designated aim point. The Paveway series has been in US service since Vietnam; modern LGBs add GPS backup.
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    LH2 — Liquid Hydrogen
    A cryogenic high-performance fuel used in upper stages, offering the highest chemical specific impulse.
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    LHA — Landing Helicopter Assault
    A large amphibious assault ship supporting helicopters, aircraft and Marine landing forces.
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    LHD — Landing Helicopter Dock
    Large amphibious assault ship (e.g., Wasp-class) carrying Marines, helicopters, MV-22 Ospreys, and F-35Bs. Can serve as light aircraft carrier.
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    Lidar — Light Detection and Ranging
    Active optical sensor that measures range by timing return of laser pulses. Mechanical-spinning, MEMS, OPA, and FMCW variants. Provides accurate 3D point clouds used in UGV / autonomous-vehicle SLAM and mapping.
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    Life Extension
    Programmatic and technical actions to extend a system's service life beyond its design or initially-planned end-of-life. Drives midlife upgrade, structural inspection, software refresh, and obsolescence-management investment.
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    LIFO — Last In, First Out
    An inventory method that issues the most recently received stock before older stock.
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    Light Time
    The one-way signal propagation time between two points. Earth-Moon: ~1.3 s; Earth-Mars: 3-22 min depending on relative positions. Critical for deep-space operations planning.
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    LLA — Latitude, Longitude, Altitude
    A geodetic coordinate triple specifying a position on the Earth’s surface and its height.
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    LLM — Large Language Model
    A model trained to predict text, used to answer, summarise and rewrite. It produces fluent output whether or not it is correct, so anything it states needs a source it did not invent.
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    LNA — Low-Noise Amplifier
    First-stage receiver amplifier that minimises added noise.
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    LNB — Low Noise Block downconverter
    A ground terminal front-end that amplifies the received signal and converts it to a lower frequency.
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    LO — Local Oscillator
    Oscillator in a receiver that mixes with the incoming signal to produce an intermediate frequency.
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    LOA — Limit of Advance
    A phase line used to control forward progress of an attack beyond which units will not advance.
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    LOAC — Law of Armed Conflict
    Body of international law (Geneva Conventions, Hague Law) governing conduct during armed conflict. Key principles: distinction, proportionality, military necessity, precaution, humane treatment. Violations constitute war crimes.
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    LOC — Lines of Communication
    Routes (land, sea, air) connecting an operating force with its base. Securing LOCs is a fundamental operational requirement.
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    LOE — Level of Effort
    A term-type contract requiring the contractor to provide a specified level of effort (labor hours) over a stated period. Payment is based on effort expended rather than deliverables produced. Used when output cannot be precisely defined.
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    LOFAR — Low-Frequency Analysis and Recording
    A passive-sonar narrowband analysis method that displays acoustic frequency content over time to detect and classify sources.
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    LOGCAP — Logistics Civil Augmentation Program
    A U.S. Army program that uses civilian contractors to augment logistics support during operations.
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    LOGPAC — Logistics Package
    A grouping of supplies and services delivered forward to sustain units during operations.
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    Loitering Munition
    A one-way attack UAV that loiters over a target area until a target is identified, then dives to detonate. Blurs the line between UAV and cruise missile. Examples: Switchblade, HERO-series, Lancet, Shahed-136. Ubiquitous in Ukraine and Nagorno-Karabakh.
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    LOLBin — Living Off the Land Binary
    A legitimate, pre-installed OS utility (PowerShell, WMI, certutil, rundll32) abused by attackers to avoid dropping custom tooling that would trigger antivirus. EDR behavioural detection is the primary counter — the binary itself is benign.
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    LOO — Line of Operations
    A line linking decisive points in time and space on the path to an objective or end state.
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    Look-Through
    Brief periodic interruptions of jammer transmission to allow the jammer platform own radar or ESM receiver to assess the target environment and adjust jamming parameters.
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    LOP-G — Lunar Orbital Platform-Gateway
    A planned small space station in lunar orbit supporting crewed missions to the Moon and beyond.
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    LoRa — Long Range spread-spectrum modulation
    A chirp spread-spectrum physical layer for long-range, low-power IoT communication.
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    LORAN — Long Range Navigation
    A terrestrial radio-navigation system using timed signals from ground stations to fix position.
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    LoRaWAN — Long Range Wide Area Network
    A low-power wide-area networking protocol built on the LoRa physical layer.
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    LOS — Line of Sight
    Unobstructed visual or RF path between two points. Required for direct-fire engagement, optical observation, and most tactical RF links. The "Observed" criterion in FOCDPIG depends on LOS.
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    LOS (Signal) — Loss of Signal
    Moment when a satellite drops below the minimum elevation mask. Not to be confused with Line of Sight.
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    LOX — Liquid Oxygen
    Cryogenic oxidiser widely used in launch propulsion.
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    LP — Listening Post
    A concealed position established forward of a defensive line to detect an approaching enemy by sound.
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    LPD — Low Probability of Detection
    Complementary to LPI — the goal of being below the noise floor of an adversary's receiver. Combined with LPI and LPE (exploitation), the three L-characteristics of covert comms.
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    LPI — Low Probability of Intercept
    Radar or communications waveform design techniques that minimise the probability of detection by adversary electronic support measures. Uses wide bandwidth, low peak power, and coded waveforms to achieve high time-bandwidth products.
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    LPTA — Lowest Price Technically Acceptable
    Source selection method where the contract is awarded to the lowest-priced offeror whose proposal meets all technical requirements. No technical trade-offs considered.
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    LRASM — Long-Range Anti-Ship Missile
    AGM-158C derivative of JASSM-ER with passive RF seeker, ESM, and autonomous terminal guidance against ship-class targets in GPS-denied / jamming conditions. Range >900 km. Fielded on B-1B and F/A-18E/F.
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    LRF — Laser Range Finder
    A device that measures distance to a target by timing a reflected laser pulse.
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    LRHW — Long-Range Hypersonic Weapon (Dark Eagle)
    US Army ground-launched hypersonic strike system using the Common Hypersonic Glide Body. Range > 2,775 km at boost-glide velocities > Mach 5. First battery fielded 2024 (in Army parlance, "Dark Eagle").
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    LRIP — Low-Rate Initial Production
    The limited early production of a system to establish the manufacturing base and support testing.
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    LRU — Line-Replaceable Unit
    Modular component replaceable at the operating location.
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    LSA — Logistics Support Analysis
    The structured analysis of support requirements performed during design to optimize a system’s supportability.
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    LSD — Landing Ship, Dock
    An amphibious warfare ship with a well deck to transport and launch landing craft and vehicles.
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    LSF — Line Spread Function
    The response of an imaging system to an ideal line source, used to characterize resolution and MTF.
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    LTAN — Local Time of Ascending Node
    The mean local solar time at which a sun-synchronous satellite crosses the equator northbound. Typical values for imaging missions are 10:00–10:30 (morning) or 13:30–14:00 (afternoon).
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    LTD — Laser Target Designator
    A device that marks a target with coded laser energy for guidance of laser-seeking munitions.
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    LTDN — Local Time of Descending Node
    The mean solar time at which a satellite crosses the equator southbound, complementary to LTAN.
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    LTE — Long-Term Evolution
    A 4G mobile broadband standard based on OFDMA offering high data rates and low latency.
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    LTE-A — LTE-Advanced
    An enhancement of LTE adding carrier aggregation and higher-order MIMO for greater capacity.
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    LV — Launch Vehicle
    Rocket that delivers a payload from the surface to orbit or beyond.
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    LVLH — Local Vertical Local Horizontal
    A spacecraft-centered reference frame where one axis points toward Earth (nadir), one along the velocity vector, and one completes the right-hand system. Used for attitude specification.
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    LWIR — Long-Wavelength Infrared
    The infrared band roughly 8–14 microns, dominant for passive thermal imaging of terrestrial-temperature objects.
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    LZ — Landing Zone
    Area designated for helicopter or vertical-lift aircraft landing. LZ selection considers obstacles, slope, surface, enemy disposition, and concealment.
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