RQ-4A Global Hawk (Tier II+ HAE UAV)
On 26 January 2012, the Department of Defense announced that the Global Hawk Block 30 program would be terminated. It had been determined that though the Global Hawk Block 30 program had been initiated to provide essentially the same capability as the U-2 manned aircraft, but at a much reduced cost to both purchase and operate, these savings had not materialized. Although this was said to be "a significant disappointment," the experience with Global Hawk Block 30 was expected to help other Global Hawk programs like the US Air Force Global Hawk Block 40, NATO's Alliance Ground Surveillance (AGS), and the US Navy's Broad Area Maritime Surveillance (BAMS).
The Global Hawk (Tier II+) High-Altitude, Long-Endurance Unmanned Aerial Vehicle (HAE UAV) program was an Advanced Concept Technology Demonstration (ACTD) designed to satisfy the Defense Airborne Reconnaissance Office's (DARO) goal of providing extended reconnaissance capability to the Joint Force commander. Extended reconnaissance was defined by the Director, DARO, Major General Kenneth Israel, as "the ability to supply responsive and sustained data from anywhere within enemy territory, day or night, regardless of weather, as the needs of the warfighter dictate." Two complementary HAE UAV systems were being developed under this program, a conventional design (Tier II Plus) and an Low Observable configuration (Tier III Minus).
The Global Hawk UAV was designed to be 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 integrated sensor suite consists of SAR, EO, and IR sensors. Each of the sensors provides wide area search imagery and a high-resolution spot mode. The radar also has a ground moving target indicator mode.
The HAE UAV was expected to be capable of long dwell, broad area coverage, and continuous spot coverage of areas of interest with high resolution sensors. Global Hawk's 24-hour operationally persistent dwell would support persistently viewing and tracking targets like critical mobile targets. The Global Hawk was focused on the radar integrated into the system for all-weather, wide-area and spot capability that could provide high quality imagery with targeting accuracy.
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 provided NIIRS 6 or 5.5 depending on whether it's EO or IR. Global Hawk was designed to integrate with the existing tactical airborne reconnaissance architectures for mission planning, data processing, exploitation, and dissemination. It would 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 would support targeting accuracy of at least 20m CEP.
The Global Hawk UAV system comprises an air vehicle component (with air vehicles, sensor payloads, avionics, and data links), a ground segment (with a launch and recovery element or LRE), a mission control element (MCE) (with embedded ground communications equipment), a support element, and trained personnel.
The ground segment 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 could operate in geographically separate locations, and the MCE can be deployed with the supported command's primary exploitation site. Both ground segments would be contained in military shelters with external antennas for line-of-sight and satellite communications with the air vehicles.
The initial mission and communications requirements for the Global Hawk UAV were well documented in the Global Hawk CONOPS and ORD and IMINT Annex, particularly in the Information Exchange Requirements portion of the ORD. The specific interoperability and connectivity requirements were called out. In general, they called 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 (IES). Whether the IESs were within line of sight determined the communications path to transmit data to them. The Spiral 1 IESs were the AF-DCGS, ETRAC/MIES, TES, TEG, JSIPS-N, and potentially other appropriately equipped IESs (such as a JIC or AOC). Future spirals called for interoperability and connectivity with JSTARS, AWACS, and potentially other appropriately equipped ISR and/or battle management platforms (such as ACS or the multi-mission aircraft or MMA). Future spirals also call for sensor control from the IESs mentioned.
When linked with systems such as the Joint Deployable Intelligence Support System (JDISS) and the Global Command and Control System (GCCS), imagery could be transferred NRT to the operational commander for immediate use. HAE UAV data would be accessible for Indications and Warning (I&W), cueing, rapid strike/restrike tasking, combat assessment and further analysis up and down the chain of command within minutes of receipt.
When the RTIP program was restructured to become MP-RTIP, the sensor became part of the Global Hawk baseline program. That in itself would not have affected the Global Hawk's communications requirements. However, two MP-RTIP associated factors would cause major perturbations in the Global Hawk's CONOPS and requirements. The AESA radar implementation, while impacting SWAP and performance, allowed for additional modes and employment flexibility of the SAR mission. This would drive CONOPS and interoperability changes. The ISR portion of the JSTARS mission, which includes the CGSs as customers, had been levied on the Global Hawk. This mission would bring with it many new customers for Global Hawk data (CGSs) that were not previously considered. It also will drive a change to Global Hawk CONOPS and interoperability requirements to satisfy these new customers. MP-CDL was a potential way to satisfy the new requirements.
The HAE UAV was designed to strive for commonality with existing Command, Control, Communications, Computers, and Intelligence (C4I) architecture. Collected imagery would be transferred to theater designated exploitation sites utilizing standard formats through existing communications mediums. Selected frames of imagery and reports could then be broadcast electronically by voice or data. The operational commander would determine the preferred means of dissemination and distribution.
The system was designed to be capable of both direct line of sight communications with the ground station by a common data link or beyond line of sight through Ku band SATCOM, direct line of sight capability, good support up to 274 megabits per second (not initially supported) and 50 megabits per second by a Ku band SATCOM. In the future users detached from the ground station could directly receive imagery data from the Global Hawk.
Due to the quantities of CGS customers expected in a Global Hawk orbit area, a broadcast capability seemed to be the most likely solution. This had been referred to as a "broadcast" data link by sources, regardless of the final nature of the implementation. The MP-CDL SPO defined whether those communications requirements were for GMTI data only or also include SAR imagery. The difference in data rates between those two requirements was significant, a reminder that an aircraft C2 link (and/or redundant link) must also be resident.
Therefore, with the advent of the JSTARS mission (driven by MP-RTIP), the communications requirements for the Global Hawk EO/IR and SAR data evolved to simultaneous LOS, BLOS, and broadcast. All or part of these could have been part of MP-CDL. If only a portion of these three links were part of MP-CDL, the MP-CDL implementation had to peacefully co-exist with the remaining links. Other CONOPS considerations (for example range, data rate, latency, and anti-jam requirements), MP-CDL network management requirements, and frequency management requirements had to be considered in the overall implementation as they could have required a bridge between communications systems. The overall implementation had to be within the allowable Global Hawk SWAP limits. Consideration would be given to the station actually controlling the mission (sensor control) also controlling network and frequency management (and not the Global Hawk mission control element).
High data rates, part of any IMINT sensor, could be driven higher by data needed for such applications as coherent change detection. The data rates required by these applications had to be considered in the overall MP-CDL solution. In some cases, minimal latency could be tolerated. In other cases, particularly those affecting TST, latency could not be tolerated. GMTI data rates did not begin to approach those required for SAR imagery. Consideration had to be given to network latency for users with small antenna apertures operating in an anti-jamming environment at extreme ranges versus network (or outside the MP-CDL network) requirements for TST.
The Global Hawk, as would any other aircraft, had a see and avoid requirement, the implementation of which would naturally preclude an onboard pilot. The greatest flight regime of concern is below 50,000 feet where the majority of other aircraft operate. The bandwidth offered by an MP-CDL broadcast could have offered the possibility of using multiple cameras on the Global Hawk and displaying a panoramic view in the LRE.
When Global Hawk missions would be allocated to Army commanders, or an Army officer is the JTF commander, the Enhanced Tactical Radar Correlator (ETRAC) and Modernized Imagery Exploitation System (MIES) (or successor processors) would be responsible for image processing. If the US Air Force were to be the "lead" Service, the processor would be the Contingency Airborne Reconnaissance System (CARS). If the Navy and Marines go in first, the Joint Services Imagery Processing System-Navy (JSIPS-N) would process the imagery. The Common Ground Station (CGS) would display the imagery no matter which system processed it.
The Global Hawk system was built by a team comprised of Teledyne Ryan Aeronautical in San Diego, E-Systems in Falls Church, Virginia, Hughes, Loral, and a number of other companies that were working on various subsystems within the aircraft.
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