ASCI 638, Assignment 4.6, UAS Beyond Line of Sight Operations

The Northrop Grumman RQ-4 Global Hawk is a high altitude, long endurance (HALE) unmanned aerial system (UAS) designed primarily for intelligence, surveillance, and reconnaissance (ISR) missions.  The UAS utilizes beyond line-of-sight (BLOS) command, control, and communication (C3) links to enable operators to control and monitor the aircraft throughout its long ranging missions.  The links also allow for real-time data feed from the aircraft’s sensors (Northrop Grumman, 2007).

The Global Hawk has a wingspan of 115 feet, length of 44 feet, height of 15 feet, and a gross take-off weight 26,750.  This UAS has a range of approximately 12,000 miles, an endurance of approximately 35 hours, and can operate at altitudes up to 65,000 feet (Northrop Grumman, 2007).  The Global Hawk is equipped with a 4 foot Ku wideband satellite antenna for BLOS C3.  A Ku-band satellite provides the primary BLOS C3 relay while an Inmarsat satellite provides a back-up capability.  Ultra high frequency (UHF) radio antennas and a Dual Band Common Data Link (DBCDL) radome antenna provide line-of-sight (LOS) communication links (Northrop Grumman, 2007).  The ground control station (GCS) for the UAS comprises two separate elements: A mission control element (MCE) and a launch and recovery element (LRE).  The MCE monitors and controls the Global Hawk throughout its mission via satellite communications (Satcom) for BLOS C3.  Satcom specialists provide support for the BLOS C3 operations and equipment.  The LRE monitors and controls the aircraft during its take-offs and landings at its base of operations via LOS C3.  UHF radio equipment provide the C3 links for this element.  Communications specialists provide support for the radio equipment.  The LRE and MCE may or may not be co-located, depending on the mission requirements (Axe, 2006).  Figure 1 displays the BLOS and LOS C3 setup for the Global Hawk.

Figure 1.  The BLOS and LOS C3 links and equipment for the RQ-4 Global Hawk (Barnard, 2007).

A disadvantage of using satcom for BLOS C3 is the requirement for satellites to relay the signals.  The expense of building, launching, and operating satellites can be significant.  The specialized personnel and terminals required for a satcom system will also incur additional expense and increase the logistical footprint of the GCS (Poole, n.d.).  Another disadvantage is the latency in the signal traveling across the vast distances between the GCS, satellite, and UAS.  A significant degree of delay, availability, and continuity in communications could potentially make a UAS operating BLOS with satcom C3 unable to meet international civil aviation requirements (Mettrop, 2011, p. 5).  Transitioning a Global Hawk from BLOS to LOS control also requires careful coordination between the MCE and LRE to ensure smooth operations.  If the two elements are not co-located, clear and reliable communications are extremely important.  Personnel cannot simply walk over to coordinate with the other element in this scenario if communications are impaired or lost.

An advantage of the Global Hawk using satcom BLOS is the range at which the links can be maintained.  To increase the “radio horizon” to maintain LOS, the height of the GCS antenna and altitude of the UAS must increase.  LOS links must also be clear of any structures or objects that may obstruct the LOS (FAB Corp, 2016).  LOS C3 systems also require establishment of ground infrastructure at different locations to provide links.  Satcom system ground stations do not need to be in a given location due to the wide coverage and long range of satcom systems.  The lack of requirement for extensive ground infrastructure also means satcom systems can be more rapidly deployed and to more remote locations (Poole, n.d.).

           Military ISR missions, such those carried out by Global Hawk, are not the only application of BLOS C3 systems.  A civilian UAS could also benefit from this technology.  A civilian HALE UAS providing communications relay or wireless internet would most likely be operated BLOS from a GCS.  A scientific UAS performing high altitude atmosphere research or surveying a remote region would also benefit from satcom links.  The BLOS C3 links provided by satcom systems would allow civilian commercial and scientific UAS to operate virtually anywhere in the world without the need to establish the C3 ground infrastructure in a particular region.


References:

Axe, D.  (2006, August 6).  Inside Global Hawk.  DefenseTech.  Retrieved from

http://www.defensetech.org/2006/08/06/inside-global-hawk/

Barnard, J.  (2007, December).  Small UAV Command, Control, and Communication Issues.

Presentation from Institute of Engineering and Technology seminar, London, United Kingdom.  Retrieved from http://www.barnardmicrosystems.com/media/ presentations/IET_UAV_C2_Barnard_DEC_2007.pdf

Fleeman, Anderson, & Bird Corporation.  (2016).  Understanding Radio Line of Sight [Fact

Sheet].  Retrieved from http://www.fab-corp.com/pages.php?pageid=2

Mettrop, J.  (2011, March).  Unmanned Aircraft Systems – Availability, Continuity and Latency.

Working paper from the 23^rd meeting of Working Group F of the International Civil Aviation Organization, Paris, France.  Retrieved from www.icao.int%2Fsafety%2Facp%2Facpwgf%2Facp-wg-f-24%2Facp-wgf24-wp15%2520uas%2520rcp.doc&usg=AFQjCNFzFDtKVZLhtuzvnvyXA_pLV4XB5Q&cad=rja

Northrop Grumman.  (2007).  RQ-4 Global Hawk Maritime Demonstration System [Fact Sheet].

Retrieved from http://www.northropgrumman.com/Capabilities/RQ4Block10GlobalHawk/ Documents/GHMD-New-Brochure.pdf

Poole, I.  (n.d.).  Satellite Communications Basics Tutorial.  Radio-Electronics.com.  Retrieved

from http://www.radio-electronics.com/info/satellite/communications_satellite/satellite-communications-basics-tutorial.phpDC: U.S. Government Printing Office.