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    Terms beginning with S

    245 terms from the estate's acronym catalogue.

    S-band
    Radio frequency band spanning 2-4 GHz. Commonly used for satellite TT&C (telemetry, tracking, and command) links due to favorable propagation and manageable antenna sizes.
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    S-Box — Substitution Box
    A non-linear lookup table used in symmetric ciphers (DES, AES) to substitute input bits with output bits. Provides the confusion property essential to cipher security by destroying mathematical relationships between key and ciphertext.
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    S1 — Personnel Staff Officer
    The battalion or brigade staff officer responsible for personnel and administration.
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    S2 — Battalion/Brigade Intelligence Staff Officer
    The staff officer responsible for intelligence and security at battalion or brigade level.
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    S3 — Operations Staff Officer
    The battalion or brigade staff officer responsible for operations, plans, and training.
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    S4 — Logistics Staff Officer
    The battalion or brigade staff officer responsible for supply, maintenance, and logistics.
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    S6 — Signal/Communications Staff Officer
    The battalion or brigade staff officer responsible for communications and information systems.
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    SAA — South Atlantic Anomaly
    A region where the inner Van Allen radiation belt dips to ~200 km altitude due to the offset between Earth's magnetic and geographic axes. Spacecraft experience elevated radiation dose rates when passing through.
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    SAASM — Selective Availability Anti-Spoofing Module
    US DoD GPS receiver component providing direct-P(Y) code acquisition with crypto-keyed anti-spoofing. Legacy technology being replaced by M-code MGUE receivers but still widely fielded on platforms across all services.
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    SACEUR — Supreme Allied Commander Europe
    The NATO commander responsible for the conduct of all Alliance military operations, dual-hatted as commander of US EUCOM.
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    SACT — Supreme Allied Commander Transformation
    The NATO strategic commander responsible for driving the transformation of Alliance forces and capabilities.
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    SADA — Solar Array Drive Assembly
    The mechanism that rotates solar arrays to track the Sun and transfers power across the rotating joint.
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    SADL — Situational Awareness Data Link
    A tactical data link connecting close air support aircraft into the Link-16 network.
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    SAE — SAE International
    Mobility-engineering standards body (formerly Society of Automotive Engineers), publishing aerospace standards (AS9100 quality, ARP4754A development, ARP4761 safety) and the levels-of-driving-automation taxonomy (J3016).
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    Safe Mode
    A pre-programmed autonomous spacecraft state entered on critical anomaly. Minimises power, points solar arrays at Sun, maintains communication for recovery commanding.
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    SAG — Surface Action Group
    A group of surface combatants organized to conduct offensive surface warfare operations.
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    SALUTE — Size, Activity, Location, Unit, Time, Equipment
    A standardized format for reporting observations of enemy activity.
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    Salvo
    The simultaneous launch of multiple weapons against a target or target set. Salvo size sized to overwhelm defences (raid analysis) or bracket aiming uncertainty. Drives magazine-depth requirements on both offensive and defensive sides.
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    SAM — Surface-to-Air Missile
    Missile launched from the ground/sea to destroy aircraft or missiles.
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    Sankey Diagram
    A flow visualisation where the width of each arrow is proportional to the quantity flowing. Used in systems engineering for mass, power, data, and cost-flow analysis across subsystem boundaries.
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    SAR — Synthetic Aperture Radar
    A radar imaging technique that synthesizes a large antenna aperture by combining returns collected as the platform moves along its flight path. Achieves high-resolution imaging independent of range and weather.
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    SASE — Secure Access Service Edge
    Gartner architecture that converges SD-WAN with cloud-delivered security services (SWG, CASB, ZTNA, FWaaS) at the network edge. Users reach applications via a nearest-PoP policy decision point instead of hair-pinning through a corporate data centre.
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    SAST — Static Application Security Testing
    Analysis of application source code, bytecode, or binaries without executing it — taint tracking, data-flow analysis, pattern matching for known vulnerable APIs. Catches bugs early in CI but suffers high false-positive rates without tuning.
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    SAT — Site Acceptance Test
    Customer acceptance testing at the final installation site to verify system performance in the operational environment.
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    SATCAT — Satellite Catalog
    The public catalogue of trackable Earth-orbiting objects maintained by 18 SDS/Celestrak, identified by 5-digit Norad ID plus international designator. Contains ~28,000 objects larger than 10 cm.
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    SATCOM — Satellite Communications
    Space-based relay for voice, data, and video. Military SATCOM categories: narrowband (voice/data), wideband (high-bandwidth), protected (jam-resistant, AEHF).
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    SATCOM On-the-Move — SOTM
    Satellite communications equipment designed to operate on moving vehicles, ships, and aircraft. Requires stabilised or electronically-steered antennas with fast tracking to maintain link through manoeuvre.
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    SBA — Simulation-Based Acquisition
    An acquisition approach using modelling and simulation throughout the procurement lifecycle to evaluate proposals, manage risk, and verify performance.
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    SBAS — Satellite-Based Augmentation System
    A system (e.g., WAAS, EGNOS) broadcasting integrity monitoring data and differential corrections to improve GNSS accuracy for safety-critical applications.
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    SBCT — Stryker Brigade Combat Team
    A medium-weight brigade combat team equipped with Stryker wheeled armored vehicles.
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    SBI — Situation-Behavior-Impact
    A structured feedback model from the Center for Creative Leadership: describe the Situation, the specific observable Behavior, and the Impact on others or outcomes. Avoids personality judgements and keeps feedback actionable.
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    SBIRS — Space-Based Infrared System
    US missile warning system with GEO/HEO sensors detecting ballistic missile launches via infrared signatures. Provides initial warning to national command authority.
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    SBOM — Software Bill of Materials
    Nested inventory of all software components and dependencies in a product, including version, source, and licence. Mandated for US federal software by EO 14028; enables rapid vulnerability assessment (e.g., Log4j scope in hours not weeks).
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    SBS — System Breakdown Structure
    A hierarchical decomposition of a system into subsystems, assemblies, and components. Used for mass/power/cost budgets and programme planning.
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    SC — Stage Separation
    The event where a spent rocket stage detaches from the vehicle to shed mass during ascent.
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    SC-FDMA — Single-Carrier Frequency Division Multiple Access
    An OFDMA variant with lower peak-to-average power used on the LTE uplink.
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    SCADA — Supervisory Control and Data Acquisition
    Industrial control systems for monitoring and controlling infrastructure (power grids, water, plants). Critical infrastructure target in cyber warfare.
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    Scan Rate
    The rate at which a radar antenna sweeps through its coverage area, typically in degrees per second or RPM. Mechanical scan rates are limited by inertia; electronic scan (AESA) is near-instantaneous.
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    SCAN_SAR — ScanSAR
    A SAR mode that sweeps the beam across sub-swaths to widen coverage at the cost of resolution.
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    ScanSAR
    A SAR mode electronically steering the beam across multiple sub-swaths for very wide coverage at reduced azimuth resolution.
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    SCBA — Self-Contained Breathing Apparatus
    A wearable air supply that lets a responder breathe safely in a contaminated or oxygen-deficient area.
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    SCC — Sea Combat Commander
    The warfare commander integrating surface and undersea warfare within a strike group.
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    SCR — Signal-to-Clutter Ratio
    The ratio of target signal power to clutter power, governing target detectability in cluttered environments.
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    Scramjet — Supersonic Combustion Ramjet
    Airbreathing engine where combustion occurs in supersonic airflow, enabling sustained hypersonic cruise (Mach 5–15) without onboard oxidiser. Powers HCMs and experimental vehicles like X-51 WaveRider.
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    Screening Volume
    Ellipsoidal region around a protected spacecraft used by conjunction assessment algorithms to flag potentially hazardous objects. Typical dimensions: 5 km radial × 25 km along-track × 5 km cross-track for LEO.
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    SCTP — Stream Control Transmission Protocol
    A transport protocol providing reliable, message-oriented, multi-streamed delivery.
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    SDA — Space Domain Awareness
    Persistent monitoring of all objects in Earth orbit to support collision avoidance, threat warning, and adversary satellite activity characterisation.
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    SDB — Small Diameter Bomb
    A 250 lb-class precision-guided weapon (GBU-39 / GBU-53) designed for increased carriage and reduced collateral damage compared to 500-lb or larger bombs. Features wings for stand-off range and GPS/INS guidance.
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    SDMA — Space Division Multiple Access
    A channel-access method that reuses spectrum by spatially separating users with directional or beamformed antennas.
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    SDN — Software-Defined Networking
    An architecture that decouples the network control plane from the packet-forwarding data plane.
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    SDR — Software Defined Radio
    Radio in which signal processing traditionally done in hardware is performed in software.
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    SEAD — Suppression of Enemy Air Defences
    Temporary degradation of adversary integrated air defense capability through kinetic and non-kinetic means. Typically precedes or accompanies offensive air operations. Distinguished from DEAD (permanent destruction).
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    SEB — Single Event Burnout
    Destructive failure of a power MOSFET or IGBT caused by a single energetic particle triggering parasitic bipolar action under high drain-source voltage. Results in permanent short circuit. Mitigated by voltage derating.
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    SECDEF — Secretary of Defense
    The head of the Department of Defense and principal defense policy advisor to the President.
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    SECO — Second Engine Cut-Off
    Shutdown of the upper-stage engine, typically at orbit insertion.
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    Second Strike
    The ability to retaliate with nuclear weapons after absorbing a first strike. Essential for stable deterrence; SSBNs are the most survivable second-strike platform.
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    SEE — Single Event Effects
    The collective term for all radiation effects caused by individual particle strikes in microelectronics — including SEU, SEL, SEB, SEGR, and single event transients. Characterised by LET threshold and cross-section curves.
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    SEGR — Single Event Gate Rupture
    Destructive failure of a power MOSFET gate oxide caused by a heavy ion strike creating a localised conductive path through the dielectric. Permanently destroys the device. Mitigated by gate voltage derating.
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    SEI — Specific Emitter Identification
    Technique that fingerprints an individual emitter by its unintentional modulation and hardware imperfections.
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    SEIE — Submarine Escape Immersion Equipment
    A survival suit enabling submariners to escape from a sunken submarine and reach the surface.
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    SEL — Single Event Latchup
    A high-current condition in a semiconductor caused by a single particle strike, triggering a parasitic thyristor. Can destroy the device if power is not cycled promptly. More severe than SEU.
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    Self-Protection Jamming
    Jamming by a platform to defend itself from threats locked onto it. Built into fighter integrated defensive suites (AN/ALQ-165, AN/ALQ-214) and typically noise + deception techniques against radar and IR seekers.
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    Semi-Active Radar Homing
    A missile seeker that homes on target reflections from an illuminator carried by the launching platform or a cooperating asset. Simpler and cheaper than active homing but requires continuous illumination throughout the engagement.
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    Semi-major Axis
    Half the longest diameter of an elliptical orbit, denoted "a". For circular orbits, equals the orbital radius. Directly determines orbital period and energy.
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    Seminar Wargame
    A facilitated discussion-based wargame where participants reason through a scenario rather than executing moves on a game board. Fast, low-cost, but subject to group-think without disciplined facilitation.
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    Sensor Fusion
    The combination of data from multiple sensors to produce a richer estimate than any single sensor — track-to-track fusion (post-detection), measurement fusion (pre-detection), or covariance-intersection (correlated sensors).
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    SEP — Solar Electric Propulsion
    An architecture powering electric thrusters from solar arrays for efficient orbit raising and cruise.
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    SEU — Single Event Upset
    A transient bit flip in memory or logic caused by a single energetic particle (proton or heavy ion). Recoverable by rewriting the affected register. Frequency increases during solar particle events.
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    SEWIP — Surface Electronic Warfare Improvement Program
    The US Navy programme modernising shipboard electronic warfare capabilities in three blocks: Block 1 (ES receiver upgrade), Block 2 (next-gen ES), Block 3 (advanced EA with AESA).
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    SFD — Saturation Flux Density
    The uplink power flux density that drives a satellite transponder amplifier to saturation.
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    SFF — Self-Forging Fragment
    Warhead type that, on detonation, forms a single high-velocity penetrator (rather than scattering fragments). Used in top-attack anti-armour munitions like SADARM and BONUS.
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    SFG — Special Forces Group
    An Army Special Forces unit organized to conduct unconventional warfare and special operations in a region.
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    SFT — System Functional Test
    End-to-end functional verification of a complete system confirming all subsystems operate together correctly before environmental testing.
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    SGP4 — Simplified General Perturbations 4
    An analytical orbit propagation model used with TLE data. Accounts for drag, gravitational harmonics, and third-body perturbations at moderate accuracy.
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    SHA — Secure Hash Algorithm
    A family of cryptographic hash functions published by NIST. SHA-256 produces a fixed 256-bit digest from any input. One-way, collision-resistant, and used for digital signatures, certificates, and data integrity verification.
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    Shannon Limit
    The theoretical maximum error-free data rate for a given channel bandwidth and SNR: C = B·log2(1+SNR). Modern codes (turbo, LDPC, polar) operate within a fraction of a dB of this limit.
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    Shannon-Hartley Theorem
    C = B · log2(1 + SNR). The maximum error-free data rate over a band-limited AWGN channel of bandwidth B at signal-to-noise ratio SNR. Sets the absolute ceiling that all real codes asymptotically approach (LDPC, polar, turbo).
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    SHAPE — Supreme Headquarters Allied Powers Europe
    The headquarters of NATO’s Allied Command Operations, located in Mons, Belgium.
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    Shaped Charge
    An explosive device configured to focus the blast into a specific direction via a hollow metallic liner. The detonation forms a high-velocity jet that penetrates armour by hydrodynamic action rather than kinetic impact.
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    SHF — Super High Frequency
    Radio band from 3 to 30 GHz used for radar and satellite communication links.
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    SHIELDOSE — Shielding Dose Estimation Model
    A NASA model calculating total ionising dose behind aluminium shielding as a function of shield thickness. Used to determine required shielding mass for electronic components based on mission orbit and duration.
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    SHORAD — Short-Range Air Defense
    Air defense against low-altitude, short-range aerial threats such as aircraft, helicopters, and drones.
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    SID — Standard Instrument Departure
    A published departure procedure that guides aircraft from the runway to the en-route structure.
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    Sidelobe
    Secondary lobes of an antenna radiation pattern outside the main beam. Sidelobes can be exploited by jammers and create false targets. Sidelobe cancellation (SLC) is a key ECCM technique.
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    Sidelobe Blanking
    An ECCM technique that compares main beam and auxiliary antenna returns to reject signals entering through sidelobes. Prevents sidelobe jamming from creating false targets.
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    SIEM — Security Information and Event Management
    Platform that aggregates and correlates security event data from multiple sources across an organization for real-time threat detection, investigation, and compliance reporting. Central nervous system of a Security Operations Center.
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    SIGAD — Signals Intelligence Activity Designator
    Identifier for a SIGINT collection source.
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    SIGINT — Signals Intelligence
    Intelligence derived from the interception and analysis of electronic signals, including communications (COMINT) and radar/electronic emissions (ELINT).
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    SIGMET — Significant Meteorological Information
    A weather advisory concerning hazardous conditions such as thunderstorms, turbulence, or volcanic ash affecting aircraft.
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    SIL — Safety Integrity Level
    IEC 61508 classification (SIL 1–4) of the required risk reduction for a safety function. Each level corresponds to target failure rate ranges and engineering process rigour. Widely used in rail, process, and defense safety-critical systems.
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    SIL (Software-in-the-Loop)
    Closed-loop test where flight software executes in a non-hardware host with simulated sensors, actuators, and environment. Earliest integration opportunity; catches most interface defects before any hardware is available. Distinct from the safety SIL acronym.
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    Silent Barker
    Joint USSF / NRO GEO-SSA mission launched September 2023. Pairs Space Force ground systems with NRO-built satellites (NROL-107) to detect and track objects in the GEO belt — complements GSSAP with a different observational geometry.
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    SIMO — Single-Input Multiple-Output
    A link with one transmit antenna and multiple receive antennas for diversity gain.
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    SINCGARS — Single Channel Ground and Airborne Radio System
    US military VHF-FM tactical radio with frequency-hopping for anti-jam. Backbone of ground force communications at battalion level and below.
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    SINR — Signal-to-Interference-plus-Noise Ratio
    The ratio of desired signal power to the combined power of interference and noise.
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    SIP — Session Initiation Protocol
    A signaling protocol for establishing, modifying, and ending real-time communication sessions.
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    SIPRNet — Secret Internet Protocol Router Network
    The US DoD network for classified information up to SECRET level. Air-gapped from public internet with strict access controls and continuous monitoring.
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    SIR — Signal-to-Interference Ratio
    The ratio of signal power to co-channel interference power.
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    SISO — Single-Input Single-Output
    A link with one transmit and one receive antenna, the baseline for MIMO comparison.
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    SITREP — Situation Report
    A report providing a commander with an update on the current tactical situation and unit status.
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    Situational Leadership
    The Hersey-Blanchard model proposing that leadership style should adapt to follower readiness across four quadrants — directing, coaching, supporting, delegating. Not empirically robust but widely taught.
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    SK — Station-Keeping
    Manoeuvres to maintain a satellite within its assigned orbital slot.
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    SKU — Stock Keeping Unit
    A distinct identifier assigned to a product variant for inventory tracking and management.
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    SL — Source Level
    The acoustic intensity radiated by a source referenced to a standard distance, a key term in the sonar equation.
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    SLAM — Simultaneous Localization and Mapping
    Algorithmic family in which a robot builds a map of an unknown environment while simultaneously tracking its own position within it. Variants: EKF-SLAM, FastSLAM, graph-SLAM, ORB-SLAM (visual), LIO-SAM (lidar+inertial). Core enabler for autonomous ground / underwater navigation in GPS-denied environments.
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    Slant Range — Slant Range
    Direct line-of-sight distance from ground station to satellite, as opposed to ground range.
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    SLAR — Side-Looking Airborne Radar
    An airborne imaging radar with an antenna oriented perpendicular to the flight path to map terrain to the side of the aircraft.
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    SLBM — Submarine-Launched Ballistic Missile
    Ballistic missile fired from submarines providing survivable second-strike nuclear capability. Trident II D5 has 12,000+ km range with MIRV.
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    SLCM — Submarine-Launched Cruise Missile
    A cruise missile launched from a submarine against land or surface targets.
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    SLOC — Sea Lines of Communication
    The primary maritime routes used for trade, logistics and naval movement between ports.
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    SLQ — AN/SLQ Electronic Warfare Set
    The designation series for shipboard electronic-warfare and countermeasures systems.
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    SM-2 — Standard Missile 2
    A medium- to long-range shipboard surface-to-air missile for fleet area air defense.
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    SM-3 — Standard Missile-3
    US sea-based exoatmospheric kinetic interceptor launched from Aegis ships. Intercepts medium and intermediate-range ballistic missiles in midcourse phase.
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    SM-6 — Standard Missile 6
    An extended-range shipboard missile providing air defense, terminal BMD and anti-surface capability.
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    SMA — Semi-Major Axis
    Half the long axis of an orbital ellipse; sets the orbital period via Kepler’s third law.
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    SmallSat — Small Satellite
    A satellite under ~500 kg wet mass. Encompasses microsats (10–100 kg), nanosats / CubeSats (1–10 kg), and picosats (<1 kg). The class that drove the New Space rideshare-economics revolution post-2010.
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    SMART Goals — Specific, Measurable, Achievable, Relevant, Time-bound
    A goal-setting framework ensuring objectives have all five properties so progress can be tracked and completion is unambiguous. A staple of performance reviews and project charters.
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    SMCM — Surface Mine Countermeasures
    Mine detection and neutralization conducted by dedicated surface mine-countermeasures ships.
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    SND — Signal-to-Noise-and-Distortion Ratio
    The ratio of signal power to the combined power of noise and harmonic distortion in a system.
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    SNMP — Simple Network Management Protocol
    A protocol for monitoring and managing devices on IP networks.
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    SNR — Signal-to-Noise Ratio
    The ratio of signal power to noise power, usually expressed in dB. Fundamental metric for communication link quality, radar detection, and sensor performance.
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    SNR_EO — Signal-to-Noise Ratio (imaging)
    The ratio of image signal to noise per pixel, governing radiometric image quality.
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    SOA — Speed of Advance
    The average speed a ship must maintain along its track to reach a destination on time.
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    SOAR — Security Orchestration, Automation and Response
    Automated cyber incident response tooling.
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    SOC — Security Operations Center
    A centralized facility staffed by security analysts who monitor, detect, investigate, and respond to cybersecurity incidents 24/7 using SIEM, EDR, and threat intelligence tools.
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    SOC2 — System and Organization Controls 2
    Audit framework assessing a service organization controls for security, availability, and confidentiality.
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    SOF — Special Operations Forces
    Units with specialized training for direct action, special reconnaissance, unconventional warfare, foreign internal defense, and counter-terrorism. US SOF under USSOCOM; JSOC for most-sensitive missions.
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    Soft Target
    Location with minimal security measures and high concentration of civilians such as shopping centers, stadiums, transit hubs, or entertainment venues. Attractive to adversaries due to accessibility and potential for mass casualties.
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    SOI — Sphere of Influence
    The region around a body where its gravity dominates, used in patched-conic interplanetary trajectory design.
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    SOJ — Stand-Off Jammer
    Dedicated jamming platform operating outside threat range to protect a strike package.
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    Solar Activity
    The general level of energetic phenomena on the Sun — sunspots, flares, coronal mass ejections — modulated by the ~11-year solar cycle. Drives upper-atmospheric density (and LEO orbital decay), GNSS scintillation, and HF propagation.
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    Solar Array
    Panels of photovoltaic cells converting sunlight to electrical power. Sized for end-of-life power after radiation degradation. Common: triple-junction GaAs (~30% efficiency).
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    Solar Flare
    A sudden release of magnetic energy on the Sun, classified by peak X-ray flux: A < B < C < M < X. Major X-class flares can drive geomagnetic storms within 1–3 days, disrupting HF, GNSS, and power-grid operations.
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    SolarWinds
    The 2020 supply-chain compromise in which nation-state actors trojanised the SolarWinds Orion build pipeline, pushing backdoored updates to ~18,000 organisations including US federal agencies. Watershed event for SBOM adoption and zero-trust mandates.
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    DiagramTry it: Cyber Warfare GuideTry it: Modern Warfare Guide
    SOLAS — Safety of Life at Sea
    The international convention setting minimum safety standards for the construction and operation of ships.
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    SOM — Scheme of Maneuver
    Commander's plan for arranging units in space and time to accomplish the mission. Distinct from but related to the Defensive Scheme of Maneuver (DSOM).
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    Sonar — Sound Navigation and Ranging
    An acoustic sensor using sound waves to detect, classify, and locate objects underwater. Active sonar transmits pulses; passive sonar listens for radiated noise.
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    SOP — Standard Operating Procedure
    A documented, repeatable procedure describing how a routine task is performed. Reduces variability, accelerates onboarding, and provides an audit baseline. Living document — updated when the underlying process or tooling changes.
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    Sortie
    A single combat or training mission flown by one aircraft, from take-off to landing. Sortie counts and sortie-generation rates are headline metrics in air-tasking-order assessment.
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    Sortie Generation Rate
    The number of sorties an aircraft (or unit) can fly per day, sustained. Function of crew rest, maintenance turnaround, weapons load times, fuel availability, and ramp space. The sustainment metric for modern air operations.
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    SoS — System of Systems
    A collection of interoperating systems delivering a capability.
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    SOSRA — Suppress, Obscure, Secure, Reduce, Assault
    The five breaching fundamentals. Suppress (3:1 minimum for deliberate, 2.5:1 for in-stride), Obscure (smoke), Secure (by fire or by force depending on threat), Reduce (clear the obstacle), Assault (pass through and seize the objective).
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    SOSUS — Sound Surveillance System
    The fixed seabed hydrophone-array network for long-range passive detection of submarines.
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    South Atlantic Anomaly
    Regional weakening of the geomagnetic field over the South Atlantic allowing the inner Van Allen belt to dip to ~200 km altitude. LEO spacecraft experience elevated SEU rates and may disable sensitive instruments during SAA crossings.
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    SOW — Statement of Work
    A document defining the specific work to be performed under a contract, including deliverables, schedule, standards, and acceptance criteria.
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    SP — Start Point
    A location on a route where a moving unit falls under the control of the designated march commander.
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    Space Fence
    A US S-band radar system on Kwajalein Atoll providing uncued, wide-field-of-view surveillance capable of detecting objects as small as 10 cm in LEO.
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    Space Segment
    The portion of a space mission comprising the satellite(s) in orbit, including the platform (bus) and payload, along with any inter-satellite links.
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    Space Weather
    The dynamic conditions in the solar wind, magnetosphere, ionosphere, and thermosphere driven by the Sun. Affects spacecraft electronics, GNSS accuracy, HF radio, polar-route aviation crew dose, and power-grid stability.
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    Space-Track
    The US Space Force public SSA data service (space-track.org) that distributes TLE sets, CDMs, decay predictions, and fragmentation notices to authenticated commercial, civil, and international users.
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    SpaceWire
    ECSS-E-ST-50-12 high-speed (2–400 Mbit/s) point-to-point serial link standard, widely used in spacecraft on-board data handling. Routed via SpaceWire routers; ECSS-E-ST-50-52 adds RMAP for memory-mapped access.
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    SPAWAR — Space and Naval Warfare Systems Command
    The former command (now NAVWAR) for naval information-warfare and C4ISR systems.
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    Speaking Up
    A psychological-safety construct: the willingness of team members to raise concerns, errors, or dissent without fear of retribution. Edmondson's research links it directly to team learning rate and error-recovery performance.
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    Spectrum Management
    Coordinating frequency assignments across competing users to prevent interference. National regulators (FCC, Ofcom, ANFR) and the ITU manage civil allocations; military spectrum management offices coordinate exercise, deployment, and crisis bands.
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    SPENVIS — Space Environment Information System
    ESA's web-based space environment analysis tool integrating radiation belt models (AE9/AP9), solar particle fluence, trapped particle spectra, and dose-depth calculations for mission planning and component selection.
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    SPG — AN/SPG Fire-Control Radar
    The designation series for shipboard fire-control (illuminator) radars for missile guidance.
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    SPI — Schedule Performance Index
    An Earned Value Management metric: Earned Value ÷ Planned Value. A value below 1.0 indicates the project is behind schedule; above 1.0 indicates ahead of schedule.
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    SPICE — Spacecraft Planet Instrument C-matrix Events
    NASA NAIF's toolkit and kernel system for computing spacecraft and planetary geometry, ephemerides, and orientation.
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    SPJ — Self-Protection Jammer
    Onboard jammer that protects the host platform by countering threat radars targeting it.
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    SPOD — Seaport of Debarkation
    A seaport through which personnel and materiel enter a theater of operations by sea.
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    SPOE — Seaport of Embarkation
    A seaport from which personnel and materiel depart for movement to a theater of operations.
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    Spoofing (GNSS)
    Transmission of counterfeit GNSS signals deceiving a receiver into calculating incorrect position or time. Distinguished from jamming (denial) by providing false information.
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    Spotlight (SAR)
    A SAR mode steering the antenna beam to illuminate a fixed target area for extended time, achieving very high azimuth resolution over a small scene.
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    SPOTREP — Spot Report
    A concise, timely report of essential information about an event or observation as it occurs.
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    SPQ — AN/SPQ Radar Set
    The designation series for special-purpose shipboard radar and fire-control systems.
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    SPS — AN/SPS Search Radar
    The designation series for shipboard air- and surface-search radar sets.
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    SPT (Support Force) — Support Force
    First element of breach organisation under SOSRA. Suppresses enemy positions with direct and indirect fires to enable the Breach Force to operate.
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    SPY — AN/SPY Radar
    The phased-array air-search and fire-control radar series central to the Aegis combat system.
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    SQLI — SQL Injection
    Attack that inserts malicious SQL into an input to manipulate a database query.
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    SQQ — Sonar Set (Combined/Suite)
    The AN/SQQ designation series for combined surface-ship sonar suites integrating multiple sensors.
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    SQR — Towed-Array Sonar Receiver
    The AN/SQR designation series for passive towed-array sonar receivers used in long-range ASW.
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    SQS — Surface Sonar Set (Hull-Mounted)
    The AN/SQS designation series for hull-mounted active/passive sonar systems on surface ships.
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    SR — Special Reconnaissance
    Reconnaissance and surveillance conducted by special operations forces to obtain information of strategic value.
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    SRB — Solid Rocket Booster
    Strap-on solid-propellant motor providing high thrust at liftoff.
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    SRBM — Short-Range Ballistic Missile
    Ballistic missiles with range under 1,000 km. Most proliferated missile class globally with short flight times (3-5 minutes) compressing defender reaction windows.
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    SRF — Spectral Response Function
    The relative sensitivity of a sensor band as a function of wavelength.
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    SRP — Solar Radiation Pressure
    The momentum transfer from solar photons impacting a spacecraft surface, exerting a force of ~4.56 µN/m² at 1 AU. A significant orbit perturbation for high area-to-mass ratio objects and a primary attitude disturbance torque source.
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    SRR — System Requirements Review
    A milestone review evaluating completeness and correctness of system requirements before proceeding to preliminary design.
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    SRU — Shop Replaceable Unit
    A subassembly within an LRU that is replaced at a repair shop or depot rather than in the field.
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    SS — Submarine
    A conventionally powered (diesel-electric) submarine designed for undersea operations.
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    SSA — Space Situational Awareness
    The knowledge and characterisation of the space environment, including location and function of space objects, to support safe and sustainable space operations.
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    SSBN — Nuclear Ballistic Missile Submarine
    Nuclear-powered submarine carrying SLBMs as part of the nuclear triad. Columbia-class replacing Ohio-class; each carries 16 Trident II D5 SLBMs.
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    SSDS — Ship Self-Defense System
    An integrated combat system coordinating sensors and weapons for close-in ship self-defense.
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    SSE — Security Service Edge
    The security half of SASE — cloud-delivered SWG, CASB, and ZTNA without the SD-WAN side. Useful when networking is already solved (or owned by a different team) and only the security plane needs modernising.
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    SSGN — Guided-Missile Submarine, Nuclear
    A nuclear-powered submarine armed with cruise missiles and capable of special-operations support.
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    SSH — Secure Shell
    A cryptographic protocol for secure remote login and command execution over a network.
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    SSK — Attack Submarine (Diesel-Electric)
    A conventionally powered hunter-killer submarine optimized for anti-submarine and anti-surface warfare.
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    SSKP — Single Shot Kill Probability
    The probability that a single engagement (one weapon fired at one target) results in target destruction. Depends on guidance accuracy, warhead lethality, and fuze reliability.
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    SSN — Nuclear Attack Submarine
    Nuclear-powered fast attack submarine for ASW, anti-surface warfare, ISR, and strike missions. Virginia-class features Virginia Payload Tubes for Tomahawk.
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    SSO — Sun-Synchronous Orbit
    A near-polar LEO where the orbital plane precesses at the same rate as Earth's revolution around the Sun (~0.9856 deg/day), maintaining consistent solar illumination at each latitude crossing.
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    SSP — Sound Speed Profile
    The variation of sound speed with depth in the water column, which governs acoustic ray propagation.
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    SSPA — Solid State Power Amplifier
    A semiconductor-based RF power amplifier used as a compact alternative to traveling wave tubes.
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    SSR — Secondary Surveillance Radar
    A radar that interrogates aircraft transponders to obtain identity and altitude in addition to position.
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    SSRF — Server-Side Request Forgery
    Vulnerability where an attacker induces a server to make requests to unintended internal resources.
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    SST — Space Surveillance and Tracking
    The detection, cataloging, and orbit determination of space objects using radar and optical sensors.
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    ST — Star Tracker
    An optical sensor that images star fields and matches them to a catalog to determine precise inertial attitude.
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    Stafford Act
    US federal law (42 USC 5121) authorizing federal disaster assistance including military support when the President declares a major disaster or emergency. The legal gateway for Defense Support of Civil Authorities (DSCA) in domestic disaster response.
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    Staging
    Sequential jettisoning of emptied propellant tanks during ascent to reduce dry mass and improve the rocket equation result. Two- and three-stage launch vehicles achieve orbital Δv budgets impossible for single-stage designs.
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    Stakeholder Management
    The systematic identification, prioritisation, and engagement of individuals or groups affected by or affecting a programme. Tools: stakeholder map, salience matrix (power × interest × legitimacy), engagement plan. Often the difference between technical success and programme success.
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    STANAG — NATO Standardization Agreement
    A document defining processes, procedures, terms, and conditions for common military or technical procedures used by NATO member nations. STANAG 4609 (motion imagery), 4586 (UAV control), 5066 (HF data link) are widely cited.
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    STANAG-4586
    NATO standard defining interfaces for unmanned aircraft systems — vehicle-specific module, data link, and command-and-control interface — to enable multi-UAS interoperability across nations. Mandated for many NATO Class II/III UAS.
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    Standoff
    The operational practice of engaging targets from outside the lethal envelope of their defences. Enables strike without exposing the launch platform to surface-to-air threats — the driving requirement for cruise missiles and glide bombs.
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    Standoff Jamming
    Jamming from platforms that never enter threat envelopes, projecting power into the target area from outside. Long-range high-ERP platforms provide area effects at the cost of propagation losses and screening geometry.
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    STAP — Space-Time Adaptive Processing
    Radar processing to suppress clutter and jamming.
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    STAR — Standard Terminal Arrival Route
    A published arrival procedure that transitions aircraft from the en-route structure to an approach.
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    STAR Framework — Situation-Task-Action-Result
    A structured decision analysis and communication framework for behavioural interviewing, decision documentation, and after-action reviews.
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    Star Tracker
    A high-precision attitude sensor that determines spacecraft orientation by imaging star patterns and matching them against a star catalogue. Typical accuracy: <10 arcseconds.
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    Starshield
    SpaceX's defence-services variant of Starlink. Hardened bus, classified payloads, NRO contract for proliferated LEO ISR + comms. Distinct production line from commercial Starlink.
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    Station Keeping
    Orbital manoeuvres performed to maintain a satellite within its assigned orbital position or box, counteracting natural perturbations — drag in LEO, lunisolar gravity in GEO, solar radiation pressure at all altitudes. Requires periodic delta-v expenditure from a limited propellant budget. GEO assets perform N-S and E-W station keeping on a regular cadence.
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    STCA — Short-Term Conflict Alert
    A ground-based tool that warns controllers of predicted loss of separation between aircraft within a short time horizon.
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    Stigmergy
    Indirect coordination among agents via modifications to a shared environment (rather than direct messaging). Classic example: ants laying pheromone trails. Used in some swarm robotics approaches for scalable coordination with intermittent comms.
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    Stinger
    FIM-92 man-portable air defense system (MANPADS) using IR/UV dual-band seeker. Shoulder-fired with ~4.8 km range. Fire-and-forget.
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    STIX — Structured Threat Information Expression
    Standardized language for representing and sharing cyber threat intelligence.
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    STK — Systems Tool Kit
    A widely used commercial software environment for modeling orbits, coverage, and mission analysis.
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    STOL — Short Take-Off and Landing
    Aircraft needing only a short runway for take-off and landing.
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    STOM — Ship to Objective Maneuver
    A maneuver concept projecting forces from ships directly to inland objectives without a beachhead.
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    STP — Spanning Tree Protocol
    A Layer 2 protocol that prevents loops by building a loop-free logical switch topology.
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    STRATCOM — Strategic Communication
    Coordinated government efforts to understand and engage audiences to advance national interests.
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    Streets-of-Coverage
    Constellation pattern where adjacent orbital planes form continuous coverage corridors at high latitudes. Trade-off: simpler design than Walker but uneven equatorial coverage. Used by Iridium, Iridium NEXT.
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    STRIDE
    Microsoft-originated threat-modeling mnemonic: Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, Elevation of Privilege. Each STRIDE class maps to a security property (authenticity, integrity, non-repudiation, confidentiality, availability, authorisation).
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    STRIP — Stripmap SAR
    A SAR mode with a fixed antenna pointing that images a continuous swath along the flight path.
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    Stripmap (SAR)
    A SAR imaging mode where the antenna beam illuminates a continuous strip of terrain as the platform moves. Moderate resolution with wide swath coverage.
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    Stryker
    US 8x8 wheeled armoured vehicle in multiple variants (ICV, SHORAD). Transportable by C-130. Balances deployability, protection, and lethality for medium-weight brigades.
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    Stuxnet
    A cyber-physical weapon discovered in 2010 targeting Iranian uranium enrichment centrifuges at Natanz. The first publicly known cyber weapon to cause physical damage to industrial equipment.
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    STW — Strike Warfare
    Offensive operations against land targets using aircraft and cruise missiles from naval forces.
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    STWC — Strike Warfare Commander
    The warfare commander responsible for planning and executing strike operations against land targets.
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    SUBSAFE — Submarine Safety Program
    The quality-assurance program ensuring the watertight integrity and recovery ability of submarines.
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    Sun-Synchronous Orbit — SSO
    A nearly-polar orbit (typically ~97–98° inclination) whose node precesses at the same rate the Earth orbits the Sun, maintaining a constant local solar time at the equator. Favoured for Earth observation.
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    Supply Chain Attack
    Compromise delivered via a trusted upstream dependency — vendor software update, npm package, compiler, or hardware component — so the malicious code inherits the legitimacy of that upstream. SolarWinds (2020) and xz-utils (2024) are canonical examples.
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    DiagramTry it: Pnt GuideTry it: Cyber Warfare GuideTry it: Modern Warfare Guide
    SURTASS — Surveillance Towed Array Sensor System
    A long, passive towed acoustic array deployed by ocean-surveillance ships for wide-area ASW.
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    Surveillance
    The systematic observation of areas, people, or things by visual, aural, electronic, or photographic means. Distinguishes from reconnaissance (a directed information-gathering mission) by being persistent rather than episodic.
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    SUW — Surface Warfare
    The naval mission area concerned with engaging enemy surface ships and defending own surface forces.
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    SUWC — Surface Warfare Commander
    The warfare commander responsible for coordinating anti-surface warfare within a strike group.
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    SV
    Schedule Variance (EV − PV). Positive means ahead of schedule, negative means behind.
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    SVP — Sound Velocity Profile
    A depth-versus-sound-speed profile used to predict acoustic propagation and sonar performance.
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    SWaP — Size, Weight, and Power
    The physical resource constraints that bound sensor and payload design, especially on small platforms.
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    SWAP-C — Size, Weight, Power, and Cost
    The combined physical and cost constraints used to evaluate sensor and payload feasibility.
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    Swarm (Robotics)
    Multi-agent unmanned system that achieves collective behaviour from simple local rules and inter-agent communication. Behaviours emerge (flocking, foraging, encirclement) without centralised control. Resilient to individual losses.
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    Swarm Tactics
    Coordinated engagement by many small autonomous platforms sharing perception and task assignment. Designed to overwhelm defenders by mass, cost-exchange ratio, and distributed lethality rather than individual capability.
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    Swath Width
    The width of the ground strip observed by a sensor in a single pass. Depends on sensor FOV, altitude, and off-nadir angle. Wider swath typically means coarser resolution.
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    SWIR — Short-Wavelength Infrared
    The infrared band roughly 1–3 microns, useful for haze penetration and detecting reflected light at night.
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    SWOT
    Strategic planning framework analysing internal Strengths and Weaknesses against external Opportunities and Threats. A staple of executive-level course development and trade studies.
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    DiagramTry it: Critical Thinking SimTry it: Aerospace Defense Industry Guide
    SysML — Systems Modeling Language
    A graphical modelling language for systems engineering. Supports specification, analysis, design, verification, and validation of complex systems. Based on UML.
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    System Test
    Integrated testing of the complete system, validating requirements that span multiple subsystems. Sits between subsystem qualification (subsystem in isolation) and operational test (system in real environment).
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