Reference library
Glossary
Plain-language definitions of the defense and counter-UAS terms used across this site, each written answer-first and deep-linkable.
88 terms
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8(a)
A U.S. Small Business Administration program that helps firms owned by socially and economically disadvantaged individuals compete, including through set-aside and sole-source contracts. Participation is time-limited and subject to eligibility rules. The 8(a) program gives eligible disadvantaged small businesses a defined lane into federal contracting, including sole-source awards; for a qualifying firm it is a major, time-limited growth window.
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Air-gapped
Describing a system that is physically isolated from unsecured networks, with no direct connection to the internet or other outside networks. Air-gapping reduces exposure to remote intrusion at the cost of convenient connectivity.
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ATO
An official management decision authorizing an information system to operate and accepting its residual risk to operations and assets. An ATO is granted after a security assessment, commonly under the Risk Management Framework.
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Attritable
Describing a system inexpensive enough that its loss in combat is acceptable, sitting between fully reusable and single-use. Attritable designs trade exquisite capability and cost for affordable numbers.
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C-UAS
The mission and technology set for detecting, tracking, identifying, and defeating hostile or unauthorized drones. It spans passive sensing and cueing through to kinetic and non-kinetic defeat, always under a human decision to engage.
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C2
The exercise of authority and direction by a commander over assigned forces to accomplish a mission. Modern C2 depends on networked systems that share a common operating picture and pass orders and reports.
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C4ISR
The integrated set of systems that lets commanders sense, decide, and direct — combining networked communications and computing with intelligence and surveillance. It is the technical backbone of situational awareness and command.
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CAGE code
A five-character code that uniquely identifies a supplier or facility to the U.S. and allied governments. It is required for entities doing business with the Department of Defense and is tied to a specific location. A CAGE code is a basic identity credential for doing business with the U.S.
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CBRN
The category of hazards posed by chemical, biological, radiological, and nuclear materials, and the detection and protection measures against them. In a sensing context it refers to detecting and identifying such hazards, not producing them.
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CCL
The list, within the EAR, of dual-use and certain military items subject to Commerce Department export control. Each entry carries an Export Control Classification Number that drives licensing requirements. The Commerce Control List tells an exporter whether a dual-use item needs a license; misreading it is a common and costly compliance failure for defense-adjacent hardware.
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Clutter
Unwanted radar returns from the environment — ground, sea, weather, buildings, or birds — that can mask real targets. Small, slow drones are hard to detect precisely because their returns sit close to the clutter floor.
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CMMC
The U.S. Department of Defense program that verifies defense contractors have implemented required cybersecurity practices, largely built on NIST SP 800-171. It introduces tiered levels and, for higher levels, independent assessment. CMMC determines whether a contractor is even eligible to hold certain DoD contracts; for a defense supplier it is a business gate as much as a cybersecurity one.
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COMINT
Signals intelligence derived from intercepting communications between people or systems. It focuses on who is communicating, from where, and where lawful, what is being said. COMINT tells an operator who is talking to whom and from where, which is often the fastest route to understanding an adversary's organization and intent even without breaking message content.
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DF
Determining the direction (bearing) from a receiver to the source of a radio transmission. Combining bearings from multiple sites, or moving a single receiver, allows the emitter to be geolocated. Direction-finding turns a raw intercept into a bearing an operator can act on; combined across sites it localizes an emitter, which is the first step toward identifying or countering it.
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DFARS
The Department of Defense's supplement to the Federal Acquisition Regulation, adding defense-specific rules and clauses, including cybersecurity and supply-chain requirements. It applies on top of the FAR for DoD contracts. DFARS adds the defense-specific clauses — including cybersecurity flowdowns — that a contractor must meet beyond the baseline FAR; missing one can make an otherwise-compliant bid non-responsive.
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DoDD 3000.09
The U.S. Department of Defense directive governing autonomy in weapon systems, requiring that they allow commanders and operators to exercise appropriate levels of human judgment over the use of force. Reissued in 2023, it sets review and design requirements rather than banning autonomy.
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Doppler
The shift in a wave's frequency caused by relative motion between source and observer. Radars exploit this shift to measure a target's radial velocity and to distinguish moving targets from stationary clutter.
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DRFM
A technology that digitally captures a radar pulse and re-transmits a modified copy, letting a jammer create realistic false targets or range and velocity deception. It is a foundational building block of modern coherent electronic attack.
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EA
The offensive division of electronic warfare: using electromagnetic energy to degrade, disrupt, or deny an adversary's use of the spectrum, for example through jamming or spoofing. Electronic attack is the offensive lever an operator uses to deny an adversary the spectrum — jamming a control link or a radar — and its effects are reversible, unlike kinetic engagement.
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EAR
The U.S. regulations, administered by the Commerce Department, that control the export of dual-use and less-sensitive military items on the Commerce Control List. Items are classified by an Export Control Classification Number.
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EAR99
The catch-all classification under the EAR for commercial items that are subject to the regulations but not listed with a specific ECCN. Most EAR99 items can ship to most destinations without a license, though restrictions on parties and end uses still apply.
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ECCN
A five-character alphanumeric code that classifies an item on the Commerce Control List and, with the destination and end use, determines whether an export license is required. Items not otherwise listed default to EAR99.
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ELINT
Signals intelligence gathered from non-communications electronic emissions, chiefly radar and other sensor signals. ELINT characterizes emitters — their frequencies, waveforms, and locations — rather than the content of messages. ELINT characterizes radars and other emitters so an operator knows what is looking at them and how to counter it; it underpins threat warning and the electronic order of battle.
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EO/IR
Imaging sensors that see in visible light (electro-optical) and heat (infrared), typically packaged together on a gimbal. They provide human-verifiable, classifiable imagery for identification but are line-of-sight and weather-limited. EO/IR gives the human-verifiable look that confirms what a radar or RF sensor only cued; for an operator it is often the sensor that turns a track into a positive identification.
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EP
The defensive division of electronic warfare: measures that protect friendly personnel and equipment from the effects of electronic attack, such as frequency agility, filtering, and emission control. Electronic protection is what keeps friendly radios, radars, and GPS working while under attack; without it, an operator's own electronic attack can be turned back on them.
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ES
The sensing division of electronic warfare: searching for, intercepting, and locating sources of radiated electromagnetic energy to build situational awareness and cue other actions. ES feeds both immediate threat warning and longer-term intelligence.
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EW
Military action that uses electromagnetic energy to sense, exploit, or deny the electromagnetic spectrum. It is conventionally divided into electronic attack, electronic protection, and electronic support. Electronic warfare is how a force fights for the spectrum it depends on; an operator who owns the electromagnetic environment can sense and communicate while denying the adversary the same.
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FAR
The primary rulebook governing how U.S. federal executive agencies buy goods and services. It sets uniform policies and standard contract clauses across the government. The FAR is the baseline rulebook for federal buying; every U.S. government contract a company pursues sits on top of it, so its clauses shape proposals, pricing, and compliance from the start.
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FMV
Continuous streaming video from a sensor, as opposed to still frames, used for tracking and identifying moving targets. FMV is a primary product of EO/IR and airborne ISR sensors. Full-motion video lets an operator track and identify a moving target continuously rather than from stills; it is the primary EO/IR product feeding real-time decisions.
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FPV drone
A drone flown by an operator wearing goggles or watching a live video feed from the aircraft's onboard camera, giving a pilot's-eye view. Low-cost FPV quadcopters have been widely adapted as improvised one-way attack munitions.
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Frequency hopping
A technique in which a transmitter rapidly changes carrier frequency across a known pseudo-random pattern, so a signal never dwells long on any one channel. It resists both narrowband jamming and easy interception.
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GNSS
The general term for satellite constellations that provide positioning, navigation, and timing worldwide, including the U.S. GPS, Europe's Galileo, Russia's GLONASS, and China's BeiDou. GNSS signals are extremely weak at the receiver, which makes them vulnerable to interference.
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GPS
The United States' satellite navigation system, and the most widely used GNSS. It provides positioning and precise timing that underpin far more than navigation, including communications and financial networks.
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GSA Schedule
A long-term, governmentwide contract administered by the GSA that lets federal buyers order commercial products and services at pre-negotiated terms and prices. Also known as the Multiple Award Schedule. A GSA Schedule gives federal buyers a fast, pre-negotiated way to buy commercial products and services; for a vendor it is a durable channel that shortens the path to award.
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GWAC
A pre-competed, multiple-award contract vehicle that any federal agency can use to buy information-technology products and services. GWACs shorten procurement time by drawing on an existing, vetted pool of vendors.
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HUBZone
A U.S. Small Business Administration program that provides contracting preferences to small businesses located in, and employing residents of, designated economically distressed areas. Certified firms can access set-aside and price-evaluation advantages. HUBZone certification gives small firms in designated distressed areas a contracting preference; for a qualifying business it is a real, geography-based competitive edge.
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Human-in-the-loop
A control arrangement in which a human must actively approve each critical action before the system carries it out. Nothing consequential happens without a deliberate human decision. Human-in-the-loop means nothing consequential happens without a person actively approving it; for operators and policy it is the strongest control point and the baseline many autonomy rules assume.
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Human-on-the-loop
A supervisory control arrangement in which an automated system can act on its own, but a human monitors it and can intervene or halt it. The human oversees rather than approves each individual action.
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Hyperspectral
Imaging that captures many contiguous, narrow wavelength bands, producing a detailed spectral signature for each pixel. This allows fine material identification but generates large volumes of data. Hyperspectral imaging fingerprints materials by their spectral signature, letting an operator distinguish, for example, a painted decoy from real vegetation that a normal camera cannot.
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IDIQ
A contract type that provides for an indefinite quantity of goods or services over a fixed period, with specific work ordered through individual task or delivery orders. It lets agencies buy repeatedly without re-competing the base contract.
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ISR
The coordinated collection and processing of information about an area or adversary to support decisions. ISR spans the sensors that collect, the platforms that carry them, and the analysis that turns data into intelligence.
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ITAR
The U.S. regulations, administered by the State Department, that control the export of defense articles, services, and technical data listed on the U.S. Munitions List. Sharing controlled technical data with a foreign person can itself count as an export.
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JADC2
A U.S. Department of Defense concept to connect sensors and shooters from all military services across every domain — air, land, sea, space, and cyber — into a single, resilient network. The goal is to move data to the right decision-maker or effector faster than an adversary can react.
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Jamming
Deliberately radiating radio-frequency energy to overpower or drown out a signal so a receiver can no longer use it — a brute-force denial of a link or a navigation signal. It is noticeable by design, because the victim receiver simply loses the signal.
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Kill chain
The sequence of steps required to counter a threat — commonly find, fix, track, target, engage, and assess. Breaking any single link in the chain defeats the engagement.
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LAWS
Weapon systems that can select and engage targets without further human intervention once activated. LAWS are the subject of ongoing policy, legal, and ethical debate over required human control. Lethal autonomous weapon systems select and engage targets without further human intervention once activated; the policy and legal debate around them directly bounds what autonomy an operator may field.
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Loitering munition
A guided weapon that flies to a target area and loiters there, searching, before diving to strike — sometimes called a "kamikaze" or one-way-attack drone. It blends attributes of a drone and a missile.
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LPI
A property of transmissions designed to be difficult for an adversary to detect, intercept, or locate, using techniques such as spread spectrum, frequency hopping, and low power. LPI links make passive RF detection of an emitter much harder.
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Maritime Domain Awareness
The effective understanding of anything in the maritime environment that could affect security, safety, the economy, or the environment. It fuses radar, transponders, imagery, and other sources into a common picture of vessels and activity at sea.
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MASINT
Intelligence derived from the distinctive measurements and signatures of a target — acoustic, seismic, thermal, radio-frequency, or material — that identify or characterize it. MASINT complements imagery and signals intelligence with physics-based detection. MASINT identifies and tracks targets by distinctive physical signatures other sensors miss; it often provides the corroboration that turns a probable identification into a confident one.
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Meaconing
Intercepting and rebroadcasting navigation or beacon signals, often with delay, to produce misleading bearings or position fixes. It is a form of deception that reuses authentic signals rather than generating new ones. Meaconing rebroadcasts navigation or beacon signals to push a receiver onto a false fix; an operator relying on that beacon may be confidently, and dangerously, wrong about position.
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MOSA
An acquisition and engineering strategy that builds systems from modular components with open, published interfaces, so parts can be upgraded or replaced by different vendors. It is now statutory guidance for major U.S. defense programs to avoid vendor lock-in.
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Multispectral
Imaging that captures a handful of discrete wavelength bands beyond ordinary color, such as near-infrared. The extra bands reveal materials and conditions the eye cannot separate. Multispectral imaging adds a few bands beyond visible color to reveal materials and conditions the eye misses; it is a lighter-weight route to material discrimination than full hyperspectral.
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MUSIC
A high-resolution direction-of-arrival estimation algorithm that separates a signal subspace from noise to resolve closely spaced emitters beyond conventional beamwidth limits. It is a standard textbook method in array signal processing. MUSIC is a high-resolution algorithm that resolves closely spaced emitters beyond what conventional direction-finding can; for an operator it means separating two nearby transmitters that would otherwise merge.
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NAICS
The standard system that classifies businesses by industry using numeric codes, used across North America for statistics and, in U.S. contracting, to define the scope of solicitations and size standards. A solicitation's NAICS code helps determine who counts as a small business for it.
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NAVWAR
Operations to protect friendly use of positioning, navigation, and timing while denying it to an adversary, without unduly disrupting civil users. NAVWAR encompasses the deliberate contest over the GNSS environment.
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NIST SP 800-171
The NIST Special Publication that specifies security requirements for protecting Controlled Unclassified Information in non-federal systems, such as those of defense contractors. Compliance with its controls is a common contractual obligation. NIST SP 800-171 defines how contractors must protect Controlled Unclassified Information on their own systems; it is the technical baseline that CMMC verifies and DFARS requires.
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OTA
A flexible U.S. government contracting mechanism, outside the standard Federal Acquisition Regulation, used to fund prototypes and research with non-traditional partners. It trades some standardization for speed and access to commercial innovators.
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Past performance
A record of how well a contractor performed on previous, relevant contracts, used by the government to assess the risk of a new award. Strong, documented past performance is often decisive in competitive selection.
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PNT
The three services — where you are, how to get somewhere, and precise time — that satellite navigation delivers and that countless systems depend on. Resilient PNT is the discipline of maintaining these when GNSS is degraded or denied.
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Positive identification
The reasonable certainty that a proposed target is a legitimate military objective before force is applied. Achieving PID typically requires corroborating evidence, often including a human-verifiable visual confirmation. Positive identification is the reasonable certainty a target is legitimate before force is used; for an operator it is both a legal requirement and the discipline that prevents fratricide and civilian harm.
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PSC
A code the U.S. government uses to describe what is being bought — the specific product or service — in a contract action. PSCs complement NAICS codes and support spending analysis and market research.
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Radar
A sensor that transmits radio waves and measures their reflections to detect targets and determine their range, bearing, and velocity. Radar works day or night and through weather, but small, slow, low-signature drones are hard to separate from clutter.
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RCS
A measure of how detectable an object is to radar — how much of the transmitted energy it reflects back toward the receiver. Small drones have a very low RCS, which is one reason they are difficult to detect.
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Remote ID
A U.S. FAA requirement (14 CFR Part 89) for most drones to broadcast identification and location information in flight, functioning like a digital license plate. It helps distinguish cooperative traffic from non-broadcasting threats.
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Replicator
A U.S. Department of Defense initiative announced in 2023 to field large numbers of low-cost, attritable autonomous systems quickly to offset an adversary's mass. It emphasizes affordable quantity and rapid delivery over exquisite, expensive platforms.
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RMF
The NIST process U.S. federal systems follow to categorize risk, select and implement security controls, assess them, and authorize the system to operate, then monitor it continuously. It provides the structured path to an Authorization to Operate.
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Rules of Engagement
The directives that define the circumstances and limitations under which forces may initiate or continue engagement. ROE translate law, policy, and command intent into concrete permissions and restrictions for operators. Rules of engagement define when and how force may be used; for an operator they translate law and policy into the specific, on-the-spot limits that govern an engagement.
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SAM.gov
The official U.S. government website where entities register to be eligible for federal contracts and grants, and where many contract opportunities are posted. Registration establishes an entity's UEI and is a prerequisite for award.
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SATCOM
Communications relayed through satellites to provide connectivity beyond line of sight and across wide areas. Military SATCOM must contend with jamming, interference, and contested access to orbital and spectrum resources. SATCOM provides connectivity beyond line of sight over wide areas; because military SATCOM must survive jamming and interference, its resilience is a direct operational concern, not just bandwidth.
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SBIR
A U.S. federal program that funds small businesses to conduct research and development with commercialization potential, in phased awards. It gives small firms non-dilutive funding to mature and transition new technology. SBIR funds small-business R&D in phases with commercialization intent; for a startup it is a non-dilutive path to prove a defense technology and win a first government customer.
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SDA
The knowledge of objects, activities, and conditions in space — tracking satellites and debris and understanding intent. SDA is the space equivalent of maintaining a recognized air or maritime picture.
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SDVOSB
A small business owned and controlled by one or more service-disabled veterans, eligible for set-aside and sole-source contracts under a dedicated federal program. The designation supports the government's contracting goals for veteran-owned firms. The SDVOSB program reserves contracts for firms owned by service-disabled veterans; for a qualifying business it is a dedicated set-aside lane with sole-source authority.
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Sensor fusion
Combining data from multiple sensors so that the result is more accurate or complete than any single sensor alone. Fusion resolves ambiguities, reduces false alarms, and builds a unified track from complementary sources.
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Set-aside
A contract or portion of a contract reserved for competition only among a defined category of businesses, such as small businesses or a specific socioeconomic group. Set-asides are a primary tool for meeting federal small-business goals.
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SIGINT
Intelligence derived from intercepting and analyzing electronic signals and communications. Its two main branches are communications intelligence (COMINT) and electronic intelligence (ELINT). Signals intelligence — COMINT and ELINT together — is how a force learns from an adversary's own emissions; for an operator it turns the electromagnetic environment into warning and understanding.
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Spoofing
Transmitting counterfeit signals that a receiver accepts as genuine, causing it to report a false position, time, or identity. Unlike jamming, spoofing aims to deceive rather than merely deny, and can go undetected.
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STTR
A U.S. federal program similar to SBIR that funds small-business R&D, but requiring formal partnership with a nonprofit research institution such as a university. It is designed to move ideas from the lab toward the market.
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sUAS
A small drone system, in U.S. regulatory terms one weighing less than 55 pounds including payload. Most commercial and hobbyist quadcopters fall in this class. Small UAS — under 55 pounds — cover most commercial and hobbyist drones and most of the counter-UAS threat; the regulatory line matters because it sets which rules and countermeasures apply.
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TDOA
A geolocation technique that fixes an emitter's position from the tiny differences in the time a signal arrives at three or more spatially separated receivers. Each pair of receivers defines a hyperbola of possible locations, and their intersection gives the position.
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TRL
A 1-to-9 scale describing how mature a technology is, from basic principles observed (TRL 1) to a proven system operating in its real environment (TRL 9). It gives programs a common language for assessing development risk.
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UAS
The complete drone system — the aircraft itself plus its ground control station, data links, and any support equipment. "UAS" refers to the whole system, not just the airframe.
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UAS Groups 1-5
The U.S. Department of Defense weight-and-performance classification of drones, from Group 1 (under 20 lb, low and slow) to Group 5 (over 1,320 lb, high-altitude, high-performance). It gives programs a shared vocabulary for the threat's size and flight envelope.
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UAV
The unmanned aircraft (airframe) alone, without the wider control and communications system around it. In current usage UAV is largely superseded by the broader term UAS. UAV names the airframe alone, and current usage largely favors UAS for the whole system; the distinction matters when a requirement or threat report means the aircraft specifically versus the full system.
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UEI
The 12-character alphanumeric identifier assigned to an entity registered to do business with the U.S. government, generated in SAM.gov. It replaced the older DUNS number as the government's standard entity ID.
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UGV
An uncrewed vehicle that operates on land, whether teleoperated or autonomous, used for reconnaissance, logistics, explosive-ordnance disposal, and other tasks that are dull, dirty, or dangerous for humans. Unmanned ground vehicles take on reconnaissance, logistics, and explosive-ordnance-disposal tasks that put crews at risk; for an operator they move danger away from people.
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USML
The list, within ITAR, of defense articles and services subject to State Department export control, organized into categories. If an item is on the USML, its export is governed by ITAR. The U.S.
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USV
An uncrewed vessel that operates on the surface of the water, used for missions such as surveillance, mine countermeasures, and logistics. USVs range from small remotely operated boats to large autonomous ships. Unmanned surface vessels perform surveillance, mine countermeasures, and logistics on the water; for a maritime operator they extend reach and endurance without risking a crew.
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