Unmanned Aerial Systems (UAS) can be controlled via two main methods: line of sight (LOS) or Beyond Line of Sight (BLOS). In LOS operations, feedback (either through direct observation or wireless link) occurs along a vector between the ground control station (GCS) and vehicle. BLOS operations extend the range of the UAS through the addition of a relay between the GSC and vehicle. The following short essay will review the BLOS command and control (C2) scheme of the General Atomics RQ-1 Predator.
BLOS Infrastructure, Support, and Procedures
The RQ-1 can be operated over the horizon using two BLOS modes. Direct Ku-band satellite relay is accomplished when an earth terminal, either Trojan Spirit or Predator Primary Satellite Link (PPSL), is co-located with the GCS (Aftergood, 2002). This significantly extends the range of the aircraft and was first successfully used for target identification in Kosovo in 1997, although it is still constrained by requiring the aircraft and GCS to be within the satellite’s Ku antenna “footprint.” The second mode, Remote-Split Operations (RSO), allows the GCS to be geographically separated from the earth terminal, but connected with a fiber optic network. This was accomplished by decoupling the data stream multiplexing and radio frequency modulation functions, with the former staying in the GCS modem, and later moving “forward” to the earth terminal site (Whittle, 2015). This was first executed in 2002, with crews in Nevada flying RQ-1s over Afghanistan, relayed through a PPSL in Germany. The additional communications infrastructure for BLOS operations increases sustainment costs for the RQ-1. In one study, it was found that 82 personnel were required to support one Predator air patrol (Boyle, 2012). However, flight-hour costs are nearly an order of magnitude less then most other U.S. Air Force aircraft at $3,679/hour (Thompson, 2013), and the BLOS architecture costs are shared among numerous users. For either BLOS C2 mode, mission crews follow a lengthy checklist of procedures to gain or lose control of the aircraft from launch and recovery crews that fly the aircraft via line of site C2 from a GCS at the deployed site (Whittle, 2015). From a human factors perspective, control of the aircraft becomes more difficult in BLOS mode, as the distance and processing equipment add 1-2 second delays between pilot inputs and aircraft response. The cumbersome checklist procedures also increase the possibility of mistakes, in a GCS already known for poor usability, resulting in mishaps from partial control or improperly configured systems.
Figure 1. Diagram of Remote Split Operations (RSO) for RQ-1 Predator. Of note, the RQ-1 is only one of several users of the fiber optic network, earth terminal, satellite, and video network. Reprinted from USAF Capabilities briefing.
BLOS Advantages and Disadvantages
BLOS operations offer two primary advantages: extended range and distributed operations. Given satellites with appropriate transponder footprints, a long-endurance aircraft could potentially fly several thousand miles (satbeams.com), keeping the GCS away from potential hazards and requiring fewer launch and recovery locations. Distributed operations provides flexibility. For the RQ-1 case, if mission crews were unable to fly in Nevada due to a natural disaster, another suitably equipped base with access to the fiber optic network could assume those duties. Additionally, if weather was poor in Afghanistan, the same Nevada-based crew could potentially be used to fly an aircraft over Kosovo. BLOS operations can also be a disadvantage. The additional network nodes and communication pathways increase the vulnerability of the total system from a network security perspective (Martellini, 2013). In the most extreme case, a Denial of Service cyber attack could render a UAS completely ineffective, a worry that is absent from manned aircraft.
Commercial BLOS Operations
The suitability of BLOS C2 for commercial operations is completely dependent on the mission, and whether that type of C2 would not be cost-prohibitive. BLOS would be appropriate for essentially any mission where flying extended-range UAS from one or few bases would be profitable. One example is BNSF Railway’s BLOS operation of Boeing-Insitu ScanEagles, which allows them to inspect thousands of miles of track from a single command center (Trimble, 2015). Other examples include agricultural survey, disaster response, and communications relay.
Conclusion
This short essay has researched the BLOS architecture for the RQ-1 Predator to understand the infrastructure, support, and procedures required for such a UAS. Benefits and shortfalls introduced with BLOS operations was also analyzed, along with applicability to commercial ventures. As with nearly any technology, propagation of BLOS UAS will depend on their ability to add value to the mission.
References
Aftergood, Steven. (2002). RQ-1 Predator MAE UAV. Retrieved from https://fas.org/irp/program/collect/predator.htm
Boyle, Ashley. (2012). The US and its UAVs: A Cost-Benefit Analysis. Retrieved from http://www.americansecurityproject.org/the-us-and-its-uavs-a-cost-benefit-analysis/
Martellini, M. (2013). Cyber security: Deterrance and IT protection for critical infrastructures. Cham: Springer.
Thompson, Mark. (2013). Costly Flight Hours. Retrieved from http://nation.time.com/2013/04/02/costly-flight-hours/
Trimble, Stephan. (2015). FAA approves beyond line of sight, urban UAV flights. Retrieved from https://www.flightglobal.com/news/articles/auvsi-faa-approves-beyond-line-of-sight-urban-uav-412021/
SatBeams SPRL. (2016). World of Satellites at Your Fingertips. Retrieved from http://www.satbeams.com/
Whittle, Richard. Predator: The Secret Origins of the Drone Revolution. New York: Picador USA, 2015. Print.
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