Translating BLOS operations to potential commercial UAS operations, a smaller platform from the Global Hawk is Scan Engle. This UAS system was approved by the FAA for BLOS operations to support railway inspection (Miller, 2015). Global Hawk could also be used for commercial applications, since it has a range of 10,000 nautical miles for 32 hours before refueling is required, and provides more options for payload configurations (“Q4 HALE,” 2012). NASA is already using the Global Hawk for atmospheric research (Naftel, 2011).
Reference
Broadway, C.(2009). Global Hawk program reaches 30,000 hours. Retrieved from http://www.afcent.af.mil/photos/380thAirExpeditionaryWing/News/Display/tabid/303/Article/445875/Global-Hawk-program-reaches-30000-hours.aspx
Chivers, M. (n.d.). Differential GPS Explained. Retrieved from http://www.esri.com/news/arcuser/0103/differential1of2.html
FAS Section 3 – Operations. (n.d.). Federation of American Scientists. Retrieved from https://fas.org/irp/doddir/usaf/conops_uav/part03.htm
Naftel, C. (2011). NASA Global Hawk: Project Overview and Future Plans. Retreived from http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110011985.pdf
Miller, P. (2015). Insitu Conducts Historic Beyond-Line-of –Sight Flights for BNSF. Retrieved from http://www.uasmagazine.com/articles/1323/insitu-conducts-historic-beyond-line-of-sight-flights-for-bnsf
Q4 HALE enterprise. (2012). Northrop Grumman Systems Corporation. Retrieved from http://www.northropgrumman.com/Capabilities/GlobalHawk/Documents/Brochure_Q4_HALE_Enterprise.pdf
RQ-4A/B Global Hawk HALE Reconnaissance UAV, United States of America. (2016). Retrieved from http://www.airforce-technology.com/projects/rq4-Global-Hawk-uav/
Global Hawk BLOS Operations
The Global Hawk operates with both line-of-sight (LOS) and beyond line-of-sight (BLOS) communications with the ground control stations (Broadway, 2009). Located under the nose fairing of the UAS, the Global Hawk has a 48 inch Ku-band antenna for satellite relay communication. “Data is transferred by Ku-band satellite communications, X-band line-of-sight links and both Satcom [satellite communication] and line of sight links at UHF-band” (“RQ-4A/B,” 2016, para. 36). This Ku-band satellite relay includes uplink and downlink of information. The Global Hawk is usually operated with a primary command and control ground station, along with separate launch and recovery ground station. Both stations have Satcom capability, along with UHF-band LOS communication with the UAS (“RQ-4A/B,” 2016).
“The pilot in the Launch and Recovery Element (LRE) of the ground segment system controls the operation of the aircraft during its automatic taxi, takeoff and landing, and is assisted by the Differential Global Positioning System (DGPS)” (“Q4 HALE,” 2016, pg. 5) . Line of sight operations is more practical for the purposes of ground maneuvering, takeoff and landing operations. There is a transition to SATCOM for the Mission Control Element (MCE) or other ground control station (GCS) (“FAS,” n.d.). For most Global Hawk operations are controlled out of Beagle Air Force Base in California. There is also another MCE located in North Dakota at Grand Forks Air Force Base (“Q4 HALE,” 2016). Satcom enables the remote operations controlled in the United States where the Global Hawk has a range to fly from these facilities “to the Persian Gulf area without refueling. Global Hawk is capable of flying at altitudes up to 60,000 feet, above inclement weather and prevailing winds for more than 32 hours” (“Q4 HALE,” 2016, pg. 4).
“Due to the unmanned capabilities of the air vehicle, the mission and flight management system and technical sophistication of the system, the deployed crew for Global Hawk is significantly smaller than the personnel required to operate a similar manned ISR platform (“Q4 HALE,” 2016, pg. 4). Beyond line of sight (BLOS) utilizing Satcom enables a broad reach of operations, limited only by the endurance of the Global Hawk UAS systems and fuel. The UAS flight plan is uploaded to the Global Hawk with waypoints, which include takeoff and landing destination instructions. On board navigation systems and sensor suite, along with GPS information allows continued operations when there is a link loss with the ground segment command pilots. This is example of some limited UAS autonomy, but is still pre-planned and monitored by a pilot in the ground control station (Broadway, 2009).
BLOS allows operations remote operations from the GCS, compared to LOS. The latter is used for direct operations, where terrain or other obstacles would not inhibit the signal relay. Just as the LRE utilizes DGPS during takeoff and landing, LOS provides direct link to telemetry and system ephemeris, allowing for more real-time accuracies. “Differential correction techniques are used to enhance the quality of location data gathered using global positioning system (GPS) receivers” (Chivers, n.d., para.1). The DGPS receiver is usually located at the landing site for the most accurate real-time position knowledge for take-off and landings. LOS is a direct link to the UAS and bypassing any potential link delay being relayed through a satellite during sensitive periods of take-off and landing operations.“The UHF SATCOM and LOS radios are interchangeable, providing an in-line spare for both links” (“FAS,” n.d., para.20). Operators follow set procedures for switching command links. Situational awareness is key to ensure no human error is induced, while taking over Satcom relay from LOS operations. There is a coordinated effort to pass this positive control from LRE to main mission operations at the MCE (“FAS,” n.d.). Referencing Figure 1, “during split-site operations, the senior operator will function as the local mission commander until air vehicle control is passed to the MCE” (“FAS,” n.d., para.20).
Figure 1: Over view of Global Hawk Relay Data Links (both LOS and BLOS) Reprinted from FAS Section 3 – Operations. (n.d.). Federation of American Scientists. Retrieved from https://fas.org/irp/doddir/usaf/conops_uav/part03.htm
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