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The RQ-4 Global Hawk is an unmanned aerial vehicle (UAV) used by the US Air Force as a surveillance aircraft. In role and design, it is somewhat similar to the Lockheed U-2, the venerable 1950's spy plane. It is a theater commander's asset to both provide a broad overview and systematically target surveillance shortfalls. The Global Hawk air vehicle is to provide high resolution Synthetic Aperture Radar (SAR)—that can penetrate cloud-cover and sandstorms—and Electro-Optical/Infrared (EO/IR) imagery at long range with long loiter times over target areas. Potential missions for the Global Hawk cover the spectrum of intelligence collection capability to support forces in worldwide peace, crisis, and wartime operations. According to the Air Force, the capabilities of the aircraft will allow more precise targeting of weapons and better protection of forces through superior surveillance capabilities.The "R" is the Department of Defense designation for reconnaissance; "Q" means unmanned aircraft system. The "4" refers to it being the fourth of a series of purpose-built unmanned reconnaissance aircraft systems. "A" or "B" refers to these being the first and second revisions, respectively. See also RQ-1 Predator, RQ-2 Pioneer, RQ-3 Dark Star, RQ-5 Hunter, RQ-6 Outrider, and RQ-7 Shadow.
The Global Hawk is the first UAV to be certified by the FAA to file its own flight plans and use civilian air corridors in the United States with no advance notice. This potentially paves the way for a revolution in unmanned flight, including that of unmanned civil passenger airliners.
1 Integrated System
The Global Hawk UAV system comprises an air vehicle segment consisting of air vehicles with sensor payloads, avionics, and data links; a ground segment consisting of a Launch and Recovery Element (LRE), and a Mission Control Element (MCE) with embedded ground communications equipment; a support element; and trained personnel.
The Integrated Sensor Suite (ISS) consists of a synthetic aperture radarSynthetic aperture radar (SAR) is a form of radar in which sophisticated post-processing of radar data is used to produce a very narrow effective beam. It can only be used by moving instruments over relatively immobile targets, but it has seen wide applic (SAR), electro-optical (EO), and infraredInfrared IR radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. The name means "below red" (from the Latin infra "below"), red being the color of visible light of longest wavelength. (IR) sensors. Either the EO or the IR sensors can operate simultaneously with the SAR. Each of the sensors provides wide area search imagery and a high-resolution spot mode. The SAR has a ground moving target indicator (GMTI) mode, which can provide a text message providing the moving target's position and velocity. Both SAR and EO/IR imagery are processed onboard the aircraft and transmitted to the MCE as individual frames. The MCE can mosaic these frames into images prior to further dissemination.
Navigation is via inertial navigation with integrated Global Positioning Systemsatellites such as this NAVSTAR have been launched since 1978. The Global Positioning System usually called GPS (the US military refers to it as NAVSTAR , is a satellite navigation system used for determining one's precise location and providing a highly updates. Global Hawk is intended to operate autonomously and "untethered" using a satellite data link (either Ku or UHF) for sending sensor data from the aircraft to the MCE. The common data link can also be used for direct down link of imagery when the UAV is operating within line-of-sight of users with compatible ground stations.
The ground segment consists of an MCE for mission planning, command and control, and image processing and dissemination; an LRE for controlling launch and recovery; and associated ground support equipment. (The LRE provides precision differential global positioning system corrections for navigational accuracy during takeoff and landings, while precision coded GPS supplemented with an inertial navigation system is used during mission execution.) By having separable elements in the ground segment, the MCE and the LRE can operate in geographically separate locations, and the MCE can be deployed with the supported command's primary exploitation site. Both ground segments are contained in military shelters with external antennas for line-of-sight and satellite communications with the air vehicles.
