The Global hawk is one of the most sophisticated UAV in operation in unmanned aviation. According with the article (Global Hawk High-Altitude Long-Endurance)  “ The Global Hawk UAV is optimized for high altitude, long range and endurance; it is to be capable of providing 28 hours of endurance while carrying 3,000 pounds of payload and operating at 65,000 feet mean sea level”. The sensory operation of the system is describe below by  (Global Hawk High-Altitude Long-Endurance)

“The integrated sensor suite consists of SAR, EO, and IR sensors. It is one of the                  most sophisticated UAV in operation.  The Global Hawk radar and EO/IR payload are carried simultaneously. Radar is capable of multiple modes -- SAR strip at one meter, SAR spot at a foot, GMTI mode down to four knots operating all at 20 to 200 kilometers range. The EO/IR payload provides NIIRS 6 or 5.5 depending on whether it's EO or IR. Global Hawk will integrate with the existing tactical airborne reconnaissance architectures for mission planning, data processing, exploitation, and dissemination. It will provide both wide area search radar and EO/IR imagery (40,000 sq. nm per mission) at 1m resolution and up to 1900 spot images per mission at 0.3m resolution, and will support targeting accuracy of at least 20m CEP”.

The system structure for the Global Hawk can be configured according to the missions with variation of air vehicles, sensors payloads, avionics, and data links. With trained personal in the ground, the recovery element with the mission control and integrated solid ground communications equipment and GCS operations and support.  

In regards to the GCS operations and the vehicles equipment and according to (Global Hawk High-Altitude Long-Endurance) consists “of the MCE for mission planning, command and control, and image processing and dissemination; the LRE for controlling launch and recovery; and associated ground support equipment. By having separable elements in the ground segment, the MCE and the LRE can operate in different separate locations, and the MCE can be deployed with the supported command’s primary exploitation site. Both ground segments are contained in military shelters with external antennas for line-of sight and satellite communications with the air vehicles. Specific  connectivity  in general,  call for the SAR, EO/IR, and GMTI data to be transmitted simultaneously via line of sight (LOS) (CDL) and beyond line of sight (BLOS) (Ku band SATCOM) to CIGSS compliant imagery exploitation systems.  The versatility of the system is capable for both direct line of sight communications with the ground station by a common data link or beyond line of sight through Ku band SATCOM. Ground stations can directly receive imagery data from the Global Hawk”

Therefore the communications can be done simultaneously BLOS and LOS. Some of the limitations to consider are when switching from LOS to BLOS, the data rate, latency, and anti-jam requirements, as this system needs good bridge between communications systems. Once the change of control is done, human factors risk and lost link are widely increased. Interactions of more ground, ATCs and air stations with satellite communications links are needed depending on the complexity of the mission. Line of sight operations imitations are present during high altitude terrain or high obstacles that limit the range of the operation.

Reduced risk in losing the UAV by constantly keeping human sight on it. The Global Hawk, have seen and avoided procedure, this future replaces an onboard pilot. Human factors are the main concern went it is flying below 50,000 feet, where heavy volume of aircrafts is operating. Multiple cameras on the Global Hawk help to reduce this risk by displaying views in the screens of the ground stations. Most of the accidents related to these UAVs have been related to some CRM deficiencies as lack in operators training, algorithms mishaps and communications between the ground controllers, the UAV and loss of satellite link. This problems need to be corrected before to integrated this systems to the NAS. More tested and improvements should be done before they can be used for commercial applications.  Actually some of these global hawks have been use by USA immigration and law enforcement sectors with some of the regulatory limitations to operate into the NAS.   

References

Bibliography

(n.d.). Global Hawk High-Altitude Long-Endurance. Ai r Force Programs.