The Northrop-Grumman (NG) made U.S. Air Force RQ-4 Global Hawk is arguably the archetypal example of a high altitude, long endurance (HALE) unmanned aerospace system (UAS) capable of missions far removed from its control station. The Global Hawk is widely used for intelligence, surveillance, and reconnaissance (ISR) missions for the military, capable of autonomous operations from taxi to flight and return to base on program. The Global Hawk takes its command and control (C2) and relays captured data in real time to control stations or operational mission commands within line-of-sight (LOS) or beyond (Loochkartt, 2014).

The RQ-4 UAS includes the air vehicle (AV), the forward-deployed Mission Control Element (MCE), and the Launch and Recovery Element (LRE) working in concert to provide command and control and sensor data transmission and control. The LRE is able to communicate with and provide C2 to the AV via transmission through a LOS common data link (CDL) and LOS ultra-high frequency (UHF) radios, as well as reaching beyond line-of-sight (BLOS) via UHF radios. However, the LRE is not capable of controlling payload sensor or receiving data captured on them. The MCE has all the capabilities of the LRE plus the ability to control sensors and receive and disseminate data. The MCE communicates and maintains situational awareness of the AV through LOS narrowband UHF radios and Ku-band UHF satellite transmission (Unmanned Aircraft Systems Roadmap 2005-2030, 2005).

In a typical Global Hawk mission the LRE prepares and launches the AV from its base station or main operations airfield, maintaining contact and C2 of the AV from taxi, launch, and recovery. The LRE hands over C2 to the corresponding MCE after launch, which maintains control of the AV and most of the mission. A Global Hawk Operations Center (GHOC) provides oversight and mission prioritization to MCEs and oversees handover procedures between LRE and MCE or between MCE and another MCE when mission re-tasking takes the AV outside the scope of its initial area of operations.

Over the last decade of war in the Middle East the Global Hawk’s capabilities as a worldwide ISR platform displays its BLOS capabilities by using extraterrestrial satellite communications (SATCOM) to relay data back to exploitation and processing centers located in the continental US (CONUS). These CONUS exploitation and processing centers processed raw data collected by the Global Hawk sensors and forwarded data to forward-deployed customers and/or other operations centers. The advantages of BLOS capabilities allows equipment and personnel at the GHOC and exploitation and processing centers to operate in relative safety at CONUS locations instead of the austere environments at forward locations. These BLOS capabilities are also attractive to civil uses such as ground mapping and high altitude visual observation. In 2013, Canada started a collaborative project with NG and NASA to use Global Hawks equipped with high-resolution cameras and synthetic aperture radar to conduct ground mapping and visual observation of the Arctic Circle (Bellamy, 2013).

Disadvantages of BLOS operations include human factors (HF) involved in the handover procedures mentioned previously, loss of situational awareness between handover participants, loss of communications link, tactical oversight, and miscommunications, amongst others, can prove to be problematic. While the MCE and LRE can provide redundancy for most C2 functions the GHOC is an essential layer of oversight and control for BLOS missions, ensuring safe and positive control of the multimillion aircraft that is the Global Hawk.

Reference

Bellamy, W. (2013, December 19). Global Hawk UAS Performs First Canadian Civil Flight - See more at: http://www.aviationtoday.cGlobal Hawk UAS Performs First Canadian Civil Flight. Retrieved from Aviation Today: http://www.aviationtoday.com/av/commercial/Global-Hawk-UAS-Performs-First-Canadian-Civil-Flight_80896.html#.U6z6Y_ldWSo

Loochkartt, G. (2014, June 25). RQ-4 Global Hawk. Retrieved from Northrop-Grumman: http://www.northropgrumman.com/Capabilities/RQ4Block20GlobalHawk/Documents/HALE_Factsheet.pdf

RQ-4 Block 20 Global Hawk. (2007, March 1).

Unmanned Aircraft Systems Roadmap 2005-2030. (2005, aUGUST 4). Retrieved from Federation of American Scientists: http://fas.org/irp/program/collect/uav_roadmap2005.pdf