Unmanned Aerial Systems Beyond Line of Sight Operations

Unmanned Aerial Systems Beyond Line of Sight Operations

US Navy MQ-4C Triton UAS

The U.S. Navy’s Broad Area Maritime Surveillance (BAMS) utilizes the United States Air Force (USAF) and Northrop Grumman RQ-4 GlobalHawk platform as a means for conducting persistent maritime aerial surveillance, and is the ideal UAS suited for long range reconnaissance and intelligence gathering missions at sea (Naval Air Systems Command, 2016). The RQ-4 boasts on station times in excess of 30 hours, a maximum flight altitude of 60,000 feet, with a direct communications link via satellite communications (SATCOM) transmitting real time intelligence data to a ground control element (Naval Air Systems Command, 2016). The UAS is equipped with electronic support measures for signals and electronic intelligence (SIGINT/ELINT) collection, inverse synthetic aperture RADAR (ISAR), and an onboard Automatic Identification System (AIS) to identify, locate, and classify maritime vessels without aircraft operator action (Rogoway, 2014). Figure 1 below highlights some of the critical components that make up the RQ-4C mission systems and illustrates some brief capability highlights associated with the UAS.

Figure 1. MQ-4C Air Vehicle Configuration. Retrieved from Naval Air Systems Command (NAVAIR), Persistent Maritime UAS, PMA-262, Patuxent River, MD. Copyright 30 November, 2011, United States Navy.

BLOS Capabilities and Architecture

Beyond line of sight (BLOS) is a capability that allows controllers of unmanned aerial systems to not be limited by direct visual contact or line of sight (LOS) telemetry or link controls. In terms of communications for the control station and other air platforms, the Triton uses Ka and X-band SATCOM links, and Link-16 network to transmit data (Naylor, 2011). Use of common control stations similar to the USAF GlobalHawk, organic/joint maintenance, common technical publications, joint launch and recovery operations and joint training are some of the methods currently employed to reduce Navy costs and minimize having to “reinvent the wheel” by using assets from the USAF (Naylor, 2011). From a human factors perspective, utilizing similar equipment, publications, procedural limitations and training requirements allows operators of the system to effectively handle advanced scenarios such as lost link, emergency procedures, and other technical issues. Valuable lessons learned from USAF operational commands deployed worldwide can pave the way for shaping Navy-specific procedures to handle lost communications or links while in a BLOS scenario, where new systems enhancements can be added to minimize lost contact time between the UAS and a control station via reestablishing SATCOM (Naylor, 2011). Navy pilots and contracted pilots are designated operators of the system, and in the effort to minimize costs and through manpower while maximizing mission effectiveness, the Triton operators simply input intended operating area, mission, and flight profile as opposed to providing direct flight control manipulations (Rogoway, 2014). Capable of covering surface intelligence for hundreds of nautical miles, SATCOM is an ideal method for monitoring Triton movement using a resilient communications link unique to military operations with robust crypto loads required for link entry (i.e. Link-16 and Ka-band) (Naylor, 2011).

As the large operational range promotes mission flexibility and wide area coverage, it also introduces an element of difficult coordination between controlling authorities. With ground control elements and forward operating bases (FOB) present in California, Florida, Maryland, Europe command (EUCOM), central command (CENTCOM) and pacific command (PACOM), communications and operational handoffs are carefully orchestrated to avoid confusion or lost tracks (Naylor, 2011). Link and track management, LOS transit and ferry, and emergencies are handled via passing responsibilities through a common ground station architecture (CGSA) (Naylor, 2011). This structure not only promotes smooth transitions of the MQ-4C flying into different regions, but also allows joint use of the asset for any operators in the CGSA. From a human factors point, this can present an issue if commonality and standardization is not addressed in regards to common operator station hardware, software (i.e. moving map, pilot display content), and operator/maintenance training (Naylor, 2011).

BLOS Autonomous Aerial Deconfliction. Ensuring safe flight operations while building in the contingency for Triton to encounter other air traffic (both military, commercial and private) while BLOS is crucial for mission success. For aerial deconfliction, the RQ-4C is equipped with the “due regard” RADAR system, a Traffic Alert Collision Avoidance System (TCAS) and Automatic Dependent Surveillance-Broadcast (ADS-B) transmitter; however these systems alone are “not considered adequate for an unmanned aircraft to sense and avoid other aircraft” (Carey, 2015). To overcome this, the Navy has been working on a thin sense and avoid (SAA) array that will be directly linked in the avionics bay into the flight logic that controls the UAS (Carey, 2016). This adjunct capability will allow for International Civil Aviation Organization (ICAO) compliance requirements that military aircraft fly with “due regard” for the safety of other aircraft when operating over international waters, and is a part of the Common Airborne Sense and Avoid (C-ABSAA) program effort (Carey, 2016). This system is intended to plan a flight pattern that includes other aircraft in close proximity into the logic, and employs probability models and algorithms as a means of advanced tracking to anticipate pilot non-response, and surveillance errors to optimize flight planning and avoid midair collisions (Broderick, 2016).

Advantages and Disadvantages of BLOS Compared to LOS. When focusing on control of the UAS, the BLOS capability provides mission flexibility to extend the surveillance range and allow for long-range overseas maritime patrol. Moving between LOS and BLOS operations is accomplished through the use of passive or active repeaters (i.e. receivers, ground-based or air-based antennae or transmitters) to relay communications between predetermined and coordinated control points (Naylor, 2011). As mentioned previously, there may be implications to transitioning between these control modes and areas of responsibility within the CGSA. A clear advantage of LOS communications and control for Triton is that SATCOM link requirements are not required, but active repeaters that are required to relay, amplify, and transmit changing frequencies in the Ka-band (or other operating bands) in order to maintain a continuous signal obligate specific external power requirements (Naylor, 2011). Not accounting for these repeater power requirements, adhering to proper maintenance of them, and failure to optimize ideal geographic positions can negatively impact the Triton’s ability to maintain contact while transiting. If position is lost during a BLOS/LOS transit, it may become difficult to reacquire the UAS location in order to facilitate an accurate handoff to another controller. Communication link integrity is “influenced primarily by antenna radiation pattern and gain, receiver sensitivity, output power, terrain relief, aircraft's attitude and trajectory, and frequency band” (Lira da Silva, Bertoli, Tosta, Ribiero & Adabo, 2016). Use of a LOS network may allow for easier troubleshooting in a lost link scenario, however continuously losing signal strength, delays, and becoming more vulnerable to data corruption may indicate a clear disadvantage of the system (Lira da Silva, Bertoli, Tosta, Ribiero & Adabo, 2016).

Commercial Applications for Railroad and Pipeline Inspections

            For the BAMS-D specifically, there are numerous application areas for a long-range maritime-based unmanned air platform, where areas such as search and rescue (SAR) and agricultural monitoring can surely benefit from this system. For other UAS that are not limited to direct visual control and observation, BLOS can greatly impact the transportation industry in terms of safety inspections. In May 2017, BNSF Railway and Rockwell Collins have completed a series of beyond line of sight UAS test flights for use in railroad track inspections (Fuller, 2017). Having this capability for test without the use of direct visual observation allows for potential future cost savings in UAS personnel support. The two companies plan on conducting additional flights with FAA permissions for more BLOS testing on railroad and pipeline inspections (Fuller, 2017). Other companies such as Lockheed Martin are also conducting testing for small unmanned aerial systems (sUAS) BLOS capability for pipeline and well inspections, claiming flight times of 45 minutes and control distances in excess of 5 kilometers, with up to 10 km possible using directional communications devices (Lillian, 2017). Pursuing this BLOS capability with UAS can greatly improve the speed and efficiency in which critical safety information is collected and transmitted for the transportation industry.

References

Broderick, T. (2016, December 7). The US Navy is preparing the MQ-4C Triton drone for service in the Pacific. Retrieved from http://nationalinterest.org/blog/the-buzz/the-us-navy-preparing-the-mq-4c-triton-drone-service-the-18663

Carey, B. (2015, April 13). Navy restarts effort to fit ‘due regard’ RADAR on Triton. Retrieved from http://www.ainonline.com/aviation-news/defense/2015-04-13/navy-restarts-effort-fit-due-regard-radar-triton

Carey, B. (2016, February 6). Navy, Northrop Grumman develop ‘sense and avoid’ for Triton. Retrieved from http://www.ainonline.com/aviation-news/defense/2016-02-05/navy-northrop-grumman-develop-sense-and-avoid-triton

Fuller, S. L. (2017, May 9). BNSF Demos More Beyond Line of Sight Drone Capabilities. Retrieved from http://www.rotorandwing.com/2017/05/09/bnsf-demos-beyond-line-sight-drone-capabilities/

Lillian, B. (2017, June 1). Lockheed Martin Takes UAV Inspection Beyond Line of Sight. Retrieved from https://unmanned-aerial.com/lockheed-martin-takes-uav-inspection-beyond-line-sight

Lira da Silva, A. L., Bertoli,G. C., Tosta, R. P., Ribeiro, M. A. & Adabo, G. J. (2016, June 7). Beyond line-of-sight UAS communication link simulation. 2016 International Conference on Unmanned Aircraft Systems (ICUAS), 135-143. doi: 10.1109/ICUAS.2016.7502601

Naval Air Systems Command. (2016). PMA-262 BAMS-D: Persistent Maritime UAS. Retrieved from http://www.navair.navy.mil/index.cfm?fuseaction=home.displayPlatform&key=624BC6D7-45CE-446C-BA1E-5818E57F9914

Naylor, W. (2011, November 14). Persistent Maritime Unmanned Aircraft Systems Program Office (PMA-262): BAMS UAS & Global Hawk Joint Efficiencies. 2011 Department of Defense Maintenance Symposium and Exhibition. Retrieved from http://www.sae.org/events/dod/presentations/2011/BAMS_UAS_AND_Global_Hawk.pdf

Rogoway, T. (2014, March 14). The Navy has the ultimate MH370 search tool, it’s just not operational. Retrieved from https://foxtrotalpha.jalopnik.com/why-mq-4c-triton-the-ultimate-mh370-search-tool-isnt-1545912657?null