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Sentinel R1
Airborne Stand-Off Radar (ASTOR)

The Sentinel R1, also known as the Airborne Stand-Off Radar, is a reconnaissance aircraft based on the Bombardier Global Express airframe. The aircraft was originally intended for conventional war-fighting tasks such as strategic reconnaissance and tracking of armored formations, but was also used in tactical intelligence roles by the United Kingdom's Royal Air Force in Afghanistan as part of Operation Herrick.

Under the mid-1980s Staff Requirement (Land/Air) 925, an existing commercial business jet aircraft was to be modified to carry the radar and air-to-ground data links. The aircraft was to be based on a modern, class-leading, large business jet. It would be able to operate above 40,000 feet and have an endurance in excess of 9 hours. The aircraft identified as suitable candidates for what became known as the Airborne Stand-Off Radar were the Bombardier Global Express and the Gulfstream V.

ASTOR was designed a ground surveillance system designed to provide information about the deployment and movement of enemy forces. It would use state-of-the-art radar technology to obtain high resolution imagery of static features and, operating in an alternate mode, it was to be capable of identifying and tracking moving vehicles. Imagery gathered would be transmitted in near-real-time to a network of distributed Ground Stations deployed with the front-line forces. Facilities within the Ground Stations would permit the display and analysis of imagery, thus ensuring that the tactical commanders were aware of the latest developments on the ground.

Experiences during operations in the Gulf in 1990-1991 further promoted the development of such a system. Widespread use of Synthetic Aperture Radar (SAR) and Ground Moving Target Indicator (GMTI) during the response to Iraq's invasion of Kuwait had clearly shown their value. In 1993, the UK Ministry of Defense approved the requirement for the ASTOR system.

In June 1999, the UK Ministry of Defence selected Raytheon Systems Limited, the UK subsidiary of the Raytheon Corporation, to build the ASTOR. The deal, worth 800 million ($1.3 billion), was one of the most intensely competed and thoroughly analyzed multi-mission programs in business aviation history. Two UK-based teams, led by Lockheed Martin Tactical Systems UK and Raytheon Systems Limited, were in competion following receipt of the 1995 Ministry of Defense project definition contracts. They were joined by a bid from Northrop Grumman for a deiravtive of the E-8 JSTARS mission systems package on a Gulfstream V.

The ASTOR system was expected to comprise 5 aircraft and 8 ground stations, together with comprehensive training and maintenance facilities at the main operating base. The equipment procurement costs were expected to be approximately 800 million. The in-service date was expected to be 2004/5, assuming contract award late 1999. Bids for the ASTOR contract were been received from Lockheed Martin, Northrop Grumman and Raytheon. The bids were under review by early 1999 and an announcement was expected in April 1999. All the proposed system solutions made extensive use of commercially available equipment to minimise risk and cost. Irrespective of the choice of eventual contractor, there will be a substantial UK industrial participation in the execution of the contract.

The joint RAF/Army battlefield surveillance system selected would be installed on 5 Bombardier Global Express business-jets, produced by Bombardier/Shorts, and would be based at RAF Waddington in Lincolnshire when it entered service, expected at that time to occur in 2005. This new capability would be supported by a team of some 350 RAF and Army personnel and some 50 civilian contractors. ASTOR consisted of a dual-mode SAR, utilizing the ASARS-2 radar technology, similar to those used by American U-2R spy planes and GMTI radar as used on the American JSTARS surveillance system. This allowed near-realtime monitoring of static and moving ground targets in all weather conditions. The Global Express aircraft was capable of operating at an altitude in excess of 45,000 feet (13,724 meters), almost twice that of J-STARS and had a range of up to 6,000 miles (9,660 kilometers). The aircraft had a mission endurance of up to 13 hours. The aircraft component was subsequently named the Sentinel R1.

The Global Express airframe offered numerous advantages over competing aircraft in its category and had set new standards in business aviation. These included the longest non-stop range in corporate aviation and a top cruise speed that reached nearly the speed of sound, as well as the largest cabin of any corporate aircraft at the time. It also featured the highest United Kingdom content by far, with 36 percent of the aircraft to manufactured in the United Kingdom. Bombardier Aerospace Shorts unit designed and manufactured 25 percent of the Global Express airframe in Belfast. Motorola, the world's leader in advanced tactical ground stations, would provide ground systems. Motorola planned to build 2 types of ground stations for the ASTOR project: Operational Level Ground Stations (OLGSs) for large, centralized headquarters facilities and Tactical Ground Stations (TGSs) for highly mobile, tactical platforms. The 8 planned ground stations were divided between 2 OLGS and 6 TGS.

The dual mode SAR/GMTI was the main sensor in the ASTOR system, enabling radar data to be available in near real time for processing and exploitation both on the platform and the ground. This provided monitoring of land-based targets to assess military capability and behaviour patterns. Targets could be classified at long range for interdiction, with wide area GMTI surveillance used to determine the position of a variety of vehicles travelling over a wide range of radial velocities.

ASTOR was not an airborne battle management or command and control system, such as JSTARs, although operators could analyze the imagery on board the aircraft, in the ground stations, and at other military sites as ASTOR passed the information in near real-time. The system would provide a 24-hour, all weather, battlefield surveillance capability. The radar range was such that the aircraft would be able to operate successfully at a safe 'Stand-off' distance behind the forward-edge-of-battle, greatly reducing the risk of loss to enemy action. ASTOR would be able to interface with the proposed military communications architecture and to be interoperable with other NATO forces. It would be a new capability for the UK Armed Forces, and the most advanced system of its kind anywhere in the world when it entered service. It would be a vital force multiplier in the modern conflict, where speed of battle was such that up-to-date information was crucial if troops were to be deployed effectively.

As part of the UK's 2010 Strategic Defence and Security Review, a successor to the Sentinel R1 and its associated ground component were planned. The Sentinel R1 would be retained at least as long as UK forces remained deployed with the International Security Assistance Force (ISAF) in Afghanistan. After that time, a new platform for the ASTOR system would be developed.

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Page last modified: 11-07-2011 02:51:18 ZULU