UNMANNED UNDERSEA VEHICLE (UUV) -  See UNMANNED UNDERWATER VEHICLE.

UNMANNED UNDERWATER VEHICLE (UUV) - An underwater vehicle launched from a torpedo tube to perform a variety of underwater scouting missions using visual imaging. [10:106]   Synonymous with UNMANNED UNDERSEA VEHICLE.  See also UNDERWATER VIEWING MODULE (UVM).

USER AGENT STRING - An alphanumeric string containing the self-identification of a BROWSER, such as Netscape or Microsoft Explorer.  []  See also MOZILLA.   EXAMPLE (1999):  Internet Explorer 4, running on Windows 98 sends the following USER AGENT STRING: User Agent: Mozilla/4.0 (compatible; MSIE 4.01; Windows 98)

V

VACUSOL - A spacecraft decoy. Sprayed from the protected spacecraft, it consists of a cloud of particles which reflect light at the same wavelengths as those reflected by the spacecraft. []

VACUUM FLUORESCENT DISPLAY (VFD) - A (vacuum tube) TRIODE consisting of a thermionic CATHODE, a control GRID, and a phosphor-coated ANODE which produces the display. []

VACUUM TUBE - An electronic device in which conduction by electrons takes place in a vacuum or gaseous medium within a gas-tight envelope (tube). Vacuum tubes generally consist of a heating element (unless it is of the COLD CATHODE variety), CATHODE, zero or more control elements (or GRID), and a plate (or ANODE). Except for electronic displays, such as the CATHODE RAY TUBE, and certain high power applications, vacuum tubes have largely been replaced by solid state devices. Also called VALVE. [] NOTES: (1) One way of classifying vacuum tubes is according to the number of elements contained in the tube. Thus, a DIODE contains two elements (cathode and plate), TRIODE contains three elements (cathode, grid, and plate), TETRODE contains four elements (cathode, two grids, and plate), and PENTODE (cathode, three grids, and plate). (2) Several types of otherwise obsolete vacuum tubes are still being manufactured in Eastern Europe (1998) for use by entertainers in guitar and other instrument amplifiers, e.g., 6L6 beam power tetrode introduced by RCA in 1936, 12AT7 dual triode, and the 12AX7 dual triode.  [10:2636]

VALUE ADDED NETWORK (VAN) - A private service that securely routes data from one organization to another for a fee.  []

VALVE - See VACUUM TUBE.

VAN ECK DEVICE - A device which monitors RF radiation from computer monitors and connecting cables.  []

VAN ECK MONITORING - The monitoring of the activity of a computer or other electronic equipment through detection of low levels of electromagnetic emissions form the device.  Named after Dr. Wim van Eck who published on the topic in 1985.  []

VARIABLE POLARIZATION - An ECCM technique for use against a main-beam on-target or STANDOFF JAMMER. It controls the POLARIZATION of the radar antenna to maximize SIGNAL-TO-JAMMING RATIO in the radar receiver. [8]

VARIABLE VELOCITY RIFLE SYSTEM (VVRS) - A rifle which vents propellant gas to vary projectile velocity for either lethal or non-lethal effects.  [10:2752]  See also NONLETHAL WEAPON.

VECTORED THRUST DUCTED PROPELLOR (VTDP) COMPOUND HELICOPTER - A specialized helicopter for airborne mine countermeasures (MCM) towing missions.  It features a ducted propellor for forward thrust and small wings for added lift.

VECTORED THRUST DUCTED PROPELLOR COMPOUND HELICOPTER

Source: ONR

VEHICLE ACTIVE DEFENSE SYSTEM (VADS) - A NONLETHAL WEAPON system consisting of a vehicle equipped with mounted flash, bang, and smoke grenades to distract, allowing the vehicle to then evade ambushers.  [10:2745]

VEHICLE MANAGER - An individual who manages the flight profile of several unmanned combat aerial vehicles (UCAVs) and/or unmanned reconnaissance aerial vehicles (URAVs) simultaneously, and is envisioned (1996) as part of a team consisting also of a weapons officer, and an intelligence analyst, all involved with the missions of these pilotless air vehicles.  [10:2586]

VEHICLE MOUNTED MINE DETECTOR (VMMD) - A vehicle-mounted system which is capable of detecting, within 0.25 meters, both surface and underground mines buried to a depth of 8 inches.  The VMMD is equipped with a forward-looking infrared sensor, a mission control computer, and a ground-penetrating standoff mine detection radar.  [10:2629]

VELOCITY GATE PULL OFF (VGPO) - A SELF-SCREENING ECM technique used against velocity tracking radars. It captures the victim radar's velocity gate, walks it off in velocity, then turns OFF, leaving the velocity gate with no signal, causing a break in the velocity track. The process is repetitive. [8] Synonymous with VELOCITY GATE WALK-OFF.

VELOCITY GATE WALK OFF - See VELOCITY GATE PULL OFF.

VERDIN - See VLF DIGITAL INFORMATION NETWORK

VERTICAL COVERAGE DIAGRAM - See FADE CHART.

VERTICAL LAUNCH ASROC (VLA) - An ASROC launched from a fixed vertical launcher.  []  ( View the VLA Program logo )

VERTICAL SITUATION DISPLAY - An electronically generated display on which information on aircraft attitude and heading, flight director commands, weapon aiming and TERRAIN FOLLOWING can be presented, choice of presentation being under control of the pilot. [1] See also HEAD-UP DISPLAY, HORIZONTAL SITUATION DISPLAY.

VERY HIGH FREQUENCY OMNI-DIRECT RADIO-RANGE (VOR) - A ground-based electronic navigation aid that transmits VHF omni-directional radio signals, 360 degrees in azimuth, oriented from magnetic north.  [10:2771]  NOTE:  The primary radio navigation aid in the National Airspace System, VOR is the internationally designated standard short-distance radio navigation aid for air carrier and general aviation Instrument Flight Rules (IFR) operations.  It provides a bearing from the aircraft to the VOR transmitter.  Distance to the ground station is provide by a co-located Distance Measuring Equipment (DME) or TACAN.  If the VOR is co-located with a TACAN, the configuration is called VORTAC.  [10:2770]

VERY LONG INSTRUCTION WORD (VLIW) - A computer instruction word which encodes four or more operations in a single instruction. []

VERY LOW FREQUENCY DIGITAL INFORMATION NETWORK - See VLF DIGITAL INFORMATION NETWORK

VIA - A vertical plated-thru hole, usually drilled, in a multi-layered Printed Circuit Board (PCB) used to provide electrical connection between two or more layers.  If the via connects two or more layers within the PCB, not including either outer layer, it is called a BURIED VIA.  If the via connects two or more layers to include one of the outer layers, it is called a BLIND VIA (BLIND TOP VIA or BLIND BOTTOM VIA).  If a via connects all layers it is called a THROUGH VIA; see the figure below.   [10:2714] 

Also called FEED-THRU (FEED-THROUGH) and VIA-HOLE.  See also MICROVIA.

VIBRATION SENSOR - A device usde to provide vibration information.  There are three basic types of vibration sensors: displacement transducer, which is a non-contact device measuring minute distances between the observed equipment and the sensor; velocity sensor (e.g. spring-held magnet moving through a coil of wire) which measures vibration as either horizontal or vertical motion; and  accelerometer, a piezoelectric device.  []

VIDEO BLANKING INTERVAL - A television (TV) broadcast area reserved for data. Internet data are delivered to the PC by using the video blanking interval in a broadcast or cable TV signal. The signal is then received by a  TV tuner card, and the incoming video is displayed in a full or one-quarter screen. []

VIDEO COMPRESSION - Techniques which allow television pictures to be transmitted over relatively narrow bands. [10:36] NOTE: Some video compression systems incorporate baseline picture frame techniques. A single frame is digitized and stored in memory. Subsequent picture frames are compared to this baseline and only the differences between the two frames are transmitted. Other techniques involve removal of alternate lines of pixels or the use of parallel processors and compression algorithms to simultaneously handle "sub-pictures".

VIRCATOR - See VIRTUAL-CATHODE OSCILLATOR.

VIRTUAL ANTENNA - A method by which a single radiating element achieves radar antenna characteristics through the use of digital processing and movement of the radiating element, target, or both. []

VIRTUAL-CATHODE OSCILLATOR (VIRCATOR) - A broadband tunable device capable of producing intense electron beams, and therefore suitable for use as a DIRECTED ENERGY WEAPON. [10:16]

VIRTUAL CIRCUIT (VC) - A PACKET SWITCHING technique in which a logical connection is established between two stations.  Communications over a virtual circuit differs from connectionless communication in that all PACKETs follow the same route, may carry less header information, and arrive in the order they were sent.  [10:2632]

VIRTUAL ENVIRONMENT (VR) - A computer-generated, three-dimensional representation of a setting, which unlike VIRTUAL REALITY, need only suggest a real or imagined space, and does not have photo-realism and a sense of total immersion a a primary goal.  [10:2595]  See also DISTRIBUTED VIRTUAL ENVIRONMENT.

VIRTUAL HEIGHT - The apparent height of an ionized layer determined from the time interval between the transmitted signal and the ionospheric echo at vertical incidence, assuming that the velocity of propagation is the velocity of light over the entire path. [3]  See also IONOSPHERE.

VIRTUAL REALITY (VE) - A combination of technologies whose interfaces with the human user can so dominate the senses that the person intuitively interacts with the immersive and dynamic computer-generated environment.  [10:2595]  Contrast with VIRTUAL ENVIRONMENT.  NOTE:   Virtual reality provides a full  immersion of the user(s) in an interactive computer-generated environment.

VIRTUAL WORLD - A loose way of describing any DISTRIBUTED VIRTUAL ENVIRONMENT, whether separately or in combination.  [10:2595]   See also CYBERSPACE.

VISIBLE LIGHT - ELECTROMAGNETIC RADIATION which can be detected by the human eye. It is commonly used to describe wavelengths which lie in the range between 0.4 and 0.7 microns. [3] See also ELECTRO-OPTIC, INFRARED, ULTRAVIOLET.

VISUALIZATION - An image- processing technique that combines the use of image processing, graphics, multi-dimensional (volume) rendering and photo-realistic rendering. [10:113]

VLF DIGITAL INFORMATION NETWORK (VERDIN) - A very low frequency (VLF)/low frequency (LF) communications system to provide secure command and control (C²) to strategic and tactical submarine forces and airborne VLF relay "Take charge and move out" (TACAMO) aircraft.  []

VOICE SYNTHESIS DEVICE - A NONLETHAL WEAPON which has the ability to clone a persons voice so that a synthesized message in that person's voice can be transmitted (e.g., by satellite) to a selected audience.  [10:2754]

VOICE TO SKULL (V2K) DEVICE -   NONLETHAL WEAPONS which include (1)   A NEURO-ELECTROMAGNETIC DEVICE  that employs microwave transmission of sound into the skull of persons or animals by way of pulse-modulated microwave radiation.  Depending upon the frequency and power densities used, such transmissions may be perceived by humans due to the ELECTROPHONIC EFFECT, which manifests itself as a buzzing or clicking sound in the back of the head.   (2)  A SILENT SOUND DEVICE which can transmit sound into the skull of person or animals.  []  Also called ARTIFICIAL TELEPATHY, MICROWAVE HEARING, FREY EFFECT. NOTE:  The sound modulation may be voice or audio sub-liminal messages.   One application of V2K is use as an electronic scarecrow to frighten birds in the vicinity of airports.

VOLATILE RAM - Computer Random Access Memory in which data cannot be retained without continuous power dissipation. [] Contrast with NON-VOLATILE RAM.

VOLCANO - A multiple mine delivery system which can deploy GATOR MINES from various vehicles and helicopters.  [10:2735]

VORTEX WEAPON - A NONLETHAL WEAPON that generates an explosive charge which creates a massive shock wave traveling at hundreds of miles per hour to its target.  [10:2730]   NOTE: This weapon can knock down people or even aircraft, and could be used in combination with gases or chemical agents.

VORTAL - A Web site that contains news, links and other information specific to one particular industrial sector.  []

VOYAGE MANAGEMENT SYSTEM (VMS) - A computerized system which includes an electronic chart display and information system.   It determines the ship's position and movement by integrating input from GLOBAL POSITIONING SYSTEM (GPS) sensors, navigation radars, depth sounder, speed log, gyrocompass, and other systems.  VMS can provide a display showing surface radar contacts superimposed on an electronic nautical chart display.  The system includes an advanced steering function to drive the ship automatically, and allows the ship to follow the course of a programmed voyage plan.  [10:2663]

VULNERABILITY - (1) The characteristics of a system which cause it to suffer a definite degradation (incapability to perform the designated mission) as a result of having been subjected to a certain level of effects in an unnatural (manmade) hostile environment. [1] (2) An electronic system measure expressed as a composite of ACCESSIBILITY, INTERCEPTIBILITY, SUSCEPTIBILITY. [4:13] See also GRACEFUL DEGRADATION.

W

WAKE VORTEX - The air turbulence generated behind an aircraft.  []

WANDERER - See SPIDER.

WAR BREAKER - A research program initiated by the Advanced Research Projects Agency (ARPA). War Breaker addresses automated surveillance, targeting, intelligence, and planning to target and destroy time-critical targets such as mobile missile systems and advanced command and control centers. [JED "Washington Report 5/93]

WARDIALER - A computer program, used by CRACKERS, which dials a specified list of telephone numbers and records those which answer with HANDSHAKE tones, distinguishing among  modem, fax, and PBX tones.  []  NOTE:   WARDIALERS have evolved from DEMON DIALERS.

WARFARE SYSTEMS ARCHITECT (WSA) - (Navy) An individual responsible for designing SYSTEM ARCHITECTURE for naval forces of the future based on requirements provided by OPNAV. []

WAR GAME - A simulation, by whatever means, of a military operation involving two or more opposing forces, using rules, data, and procedures designed to depict an actual or assumed real life situation. [1]

WARTIME RESERVE MODE (WARM) - Characteristics and operating procedures of sensor, communications, navigation aids, threat recognition, weapons, and countermeasures systems that a) will contribute to military effectiveness if unknown to or misunderstood by opposing commanders before they are used, but b) could be exploited or neutralized if known in advance. Wartime reserve modes are deliberately held in reserve for war-time or emergency use and seldom, if ever, applied or intercepted prior to such use. [1]

WATER HAMMER - A weapon used for underwater combat or mine clearing.  The device employs a phase array of shock tubes to generate and focus underwater shock waves into a pressure pulse exceeding 2,000 psi.  In effect, it is an underwater attack trumpet, destroying objects hundreds of meters distant with sound.  [10:2690]   NOTE:   The explosive wave generator for the water hammer is powered by a reactant mixture of finely granulated aluminum and seawater.   A horn forms the exit vehicle for the energy waves out of the source tube.   Converging waves reinforce each other in a zone away from the front of the source.   This ability to focus shock waves differentiates the water hammer from conventional methods of dropping explosives in the water.

WATTENBERG PLOW (WP) - A strongback with vertical cutting knives at 4-inch spacings, behind a blanket of cross-linked chains.  It is towed from a distance of about 600 feet by a helicopter at speeds up to 20 knots to clear land mines.  [10:2791]  See also CLAUSEN POWER BLADE.

WAVE - A disturbance propagated through a medium or through space. [3] NOTE: Disturbance, in this definition, is used as a generic term indicating not only mechanical displacement but also voltage, current, electric field strength, temperature, etc.

WAVE CLUTTER - CLUTTER caused by waves from the sea. [3]

WAVE DETECTION - The sensing of sub-audible atmospheric waves.  An example is the detection of clandestine nuclear explosions and rocket plume products that roll across the atmosphere and produce waves and vertical undulations as well.  Such waves travel a long way, and provide potential for detection by suitable detection devices.  [10:2655]

WAVE DISTURBER - JAMMING transmitter. [10:61]

WAVE FILTER - A TRANSDUCER for separating WAVES on the basis of their frequency. [3]

WAVEFORM - A manifestation or representation or a visualization of a WAVE, pulse, or transition. [3] EXAMPLE: The geometrical shape obtained by displaying a characteristic of the wave as a function of some variable, usually time, plotted over one primitive period (e.g., one cycle).

WAVEFORM DIVERSITY - A radar ECCM technique wherein the transmitted waveform characteristics are changed periodically or randomly to make it difficult for an ECM operator to receive, determine the lethality of, and/or effectively jam the radar. [8]

WAVELENGTH DECORRELATION - A high-resolution imaging technique for measuring target shape and estimating surface-scattering properties. [10:2504]