4.7 Research: UAS Beyond Line of Sight Operations

When most people think of drones, most often they think of the RQ-1 Predator or the armed version MQ-1 and the MQ-9 Reaper.   This is mostly due to the media highlighting their direct impact world-wide during combat operations through armed strikes.  Although both of these systems utilize both Line-of-Sights (LOS) and Beyond-Line-of Sight (BLOS) operations, people often forget about the larger RQ-4 Global Hawk which also has the same capability minus the munitions.   The role of the RQ-4 is “to provide a high-altitude, long-endurance airborne intelligence, surveillance and reconnaissance” (ISR) which includes infrared, optical and synthetic aperture radar imagining ("Rq-4b global hawk," 2012).  In addition the RQ-4 is equipped with a theater communications relay system known as BACN (Battlefield Airborne Communications Node).   All of which is very useful as long as there is a link connecting the ground unites to the aircraft.  Unfortunately direct line of sight is not always obtainable; therefore the capability of BLOS was created.  So what is exactly BLOS?  To put it simply; it is the ability to operate and or communicate beyond the physical curvature of the Earth and most manmade or natural obstructions.  So how is this accomplished today? 

At the basic level, the RQ-4’s BLOS operates primarily through Ku band Satellite Communications (SATCOM) system network (Pike).  This typically means that data is being transmitted via a ground control station up to the Satellite then down to the aircraft and back as need using the Ku band frequency range.  For most US military operations the Ku Band falls between 12 to 18 GHz, providing an optimal frequency range for large data transfers ("Satellite frequency bands," ).  As a secondary to the Ku band the RQ-4 Global Hawk is capable of transmit using INMARSAT (Loochkartt, 2014).  INMARSAT operates on a frequency range between 27 and 40 GHz and is currently used by the Department of Defense on what’s known as the Wideband Gapfiller System (WGS) satellite constellation ("Air force distributed," 2009).  This secondary links works in the same fashion as the Ku band Satellite, just with higher-powered and bandwidth ("Air force distributed," 2009).  In most cases aircraft control, collected intelligence data and relayed communication can operate simultaneously.  In some situations, the BLOS includes a LOS link as well.  For example one unit may have a direct LOS link (typically in the Ultra High Frequency range; 300-1000 MHz) with the aircraft, while completing the link using a SATCOM link to a unit that is BLOS or vice versa (Gupta, Ghonge & Jawandhiya, 2013).

Although BLOS provides the capability for pilots and sensor operators to fly and collect data from almost anywhere in the world while at home station, there are many additional elements required to accomplish this beyond the SATCOM network.  For starters, there is a Launch and Recovery Element (LRE) that is deployed with the Global Hawk at its forward operational base.  The LRE are responsible for the loading of the autonomous flight mission plan into the aircraft, and the monitor the aircraft during taxi, take off and landings (Loochkartt, 2014).  While the Mission Control Element (MCE) flies and operates the aircraft sensors from home station (Loochkartt, 2014).  The MCE works directly with the LRE team while the aircraft is on ground using BLOS and LOS for communication between them.  In addition there are the Distributed Common Ground System (DCGS) that are responsible for the collection, processing, exploitation, analysis and dissemination of ISR data ("Air force distributed," 2009).  These 11 DCGS sites communicate with the MCE element using a combination or both BLOS and LOS depending on their location ("Air force distributed," 2009).  Finally another major element is the Air Operations Center (AOC) that is responsible for the tasking of the Global Hawk asset to provide ISR and theater communications relay ("Rq-4b global hawk," 2012).  Other key players are the individuals who are in charge of maintaining and operating the equipment (aircraft, DCGS, AOC, Satellite Constellation network, GCS, etc.). 

The overall advantage to using a BLOS link is the ability to operate and communicate almost anywhere in the world regardless where the key players are located.  This is because the Ku Band Satellites “provide an overlapping world-wide coverage” Brunnenmeyer, Mills, Patel, Suarez & Kung, 2012).  In addition, the cost in hardware is relatively cheap, and that the smaller beam footprint permits the use of a smaller antenna saving both in weight and in space ("Executive summary of," ).  Finally, BLOS provides both a secure and jam resistant link (Gupta, Ghonge & Jawandhiya, 2013).

The disadvantages for starts are the reduced data transfer rates by using the BLOS.  The Ku band SATCOM is capable of transferring data at nearly 50 Megabits per Second (MPS), but this is significantly slower than LOS link which transfers data at nearly 274 MPS (Pike).  Secondly, the Ku band SATCOM systems are “reaching saturation point on the orbital arc, at which point new systems are served mainly to replace ageing systems” (Brunnenmeyer, Mills, Patel, Suarez & Kung, 2012).  Additionally Ku band systems have performance limitations beyond bandwidth, in they do not provide 100% coverage world-wide.  So in order to maintain BLOS link, “a patchwork of satellites and systems are need to provide continuous coverage such as INMARSAT” (Brunnenmeyer, Mills, Patel, Suarez & Kung, 2012).   When it comes to the Ka band; “not all military users will have access to the WGS system, as this system requires pre-coordination due to the limited number of steerable beams available” (Brunnenmeyer, Mills, Patel, Suarez & Kung, 2012).  Finally, both Ku and Ka bands signals are affected by atmospheric weather conditions; Ka more than Ku ("Executive summary of," ).

A unique human factor issues that is specific to UAS operators that switch from LOS to BLOS begins with the increase in “lack of sensory cues such as ambient visual information, kinesthetic and vestibular inputs and sound” (McCarley & Wickens).  This maybe further amplified by the distance between the operators and the operational environment of the aircraft.  Another factor is the potential impact regarding circadian rhythm and fatigue of an operator in a different time zone may need to change schedules to fulfill mission requirements.  Finally, the impact of system feedback and monitoring cues as the data link band-width is reduced significantly from LOS to BLOS operations. 

As with any military technology, there comes an opportunity for the private sector to incorporate or improve upon it; this has been done before and more than likely will continue.  As for where a UAS with BLOS can be utilized in the private sector there are many.  For starters, “law enforcement, pipeline and power line survey, aerial photography, border patrol, coastal boarders and road traffic surveillance, environmental monitoring, forestry, aerial mapping and meteorology, etc.” (Gupta, Ghonge & Jawandhiya, 2013). All of these examples can use a UAS that has a range that is not limited to the direct LOS, enabling a greater distance covered in a single mission. 

Reference:

(2012). Rq-4b global hawk high-altitude long-endurance unmanned aerial system (uas). Air Force Programs, 271-273. Retrieved from http://www.dote.osd.mil/pub/reports/FY2012/pdf/af/2012globalhawk.pdf

Air force distributed common ground system. (2009, August 31). Retrieved from http://www.af.mil/AboutUs/FactSheets/Display/tabid/224/Article/104525/air-force-distributed-common-ground-system.aspx

Brunnenmeyer, D., Mills, S., Patel, S., Suarez, C., & Kung, L. (2012). Ka and ku operational considerations for military SATCOM applications. Military Communications Conference-Track 4-System Perspectives, 1-7. doi: 10.1109/MILCOM.2012.6415563

Executive summary of the commercial satellite communications (SATCOM) report. (n.d.). Retrieved from http://fas.org/spp/military/docops/navy/commrept/

Gupta, S., Ghonge, M., & Jawandhiya, P. (2013). Review of unmanned aircraft system (uas).International Journal of advanced Research in Computer Engineering & Technology (IJACRET), 2(4), 1646-1658. Retrieved from http://www.uxvuniversity.com/wp-content/uploads/2014/04/Review-of-Unmanned-Aircraft-System-UAS.pdf

Loochkartt, G. (2014, May 02). Rq-4 global hawk maritime demonstration system. Northrop Grumman, 1 6. Retrieved from http://www.northropgrumman.com/Capabilities/RQ4Block10GlobalHawk/Documents/GHMD-New-Brochure.pdf

McCarley, J., & Wickens, C. (n.d.). Human factors concerns in uav flight. Institute of Aviation, Aviation Human Factors Division University of Illinois at Urbana-Champaign, 1-5. Retrieved from http://www.hf.faa.gov/hfportalnew/Search/DOCs/uavFY04Planrpt.pdf

Pike, J. (n.d.). Rq-4a global hawk (tier ii hae uav). Retrieved from http://fas.org/irp/program/collect/global_hawk.htm

Satellite frequency bands. (n.d.). Retrieved from http://www.marinesatellitesystems.com/index.php?page_id=101