Business & GA, Military

Taking the High Ground with ASTOR

By Ian Parker | February 1, 2000
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Since the beginning of armed conflict, those that have held the high ground had great advantages. Not only does the enemy have to fight uphill, but also they can be observed much more easily.

Today that high ground is extremely high, represented by spacecraft or aircraft—often fitted with various sensors—looking down on the Earth. Indeed, current intent is to "out sensor" the enemy by disabling his while ensuring that yours are out of harm’s way.

With this rather basic concept in mind, the United Kingdom set out to acquire airborne stand-off radar. At last year’s Paris Air Show, the UK Ministry of Defence (MoD) announced that Raytheon Systems Ltd. (RSL), the UK subsidiary of U.S.-based Raytheon Co., was the "preferred bidder" to fulfill its Airborne Stand-Off Radar (ASTOR) program (see box for the RSL-led team members). Competing bids came from Lockheed Martin and Northrop Grumman.

The $1.3-billion program will provide a radar surveillance capability during day and night and in all weather. It will supply imagery over a large area of ground (precise details are classified). This imagery can be analyzed on board the aircraft and passed in near real-time to ground stations and other military systems.

Military Global Express

"Our solution will bring great benefits to UK industry as a result of the transfer of radar, communications and systems integration technologies," says Peter McKee, RSL’s managing director. "We believe that this first major defense procurement by this government demonstrates all the elements of its smart procurement methodology," he adds, referring to current Ministry of Defence efforts to maintain efficiency and avoid procurement waste.

The platform for Raytheon’s ASTOR is the Bombardier-Shorts Global Express business jet. Capable of flying up to 50,000 feet, its endurance is 14 hours, although an in-flight refueling capability allows much longer flights, limited only by engine oil use and crew fatigue.

The antenna for the synthetic aperture radar (SAR) is mounted under the forward fuselage. By taking a series of "snapshots" and then digitally melding them into single high-resolution images, the radar will identify hostile forces and present to ASTOR crewmen their number, quantity, direction and speed. Optional optical equipment can provide additional imagery.

The information is sent via secure data links to the ground stations, which are interoperable with U.S. and NATO systems. ASTOR crewmen have options, however; they can exploit the processed images in the aircraft or transfer them for exploitation on the ground.


Data can be transmitted via secure, or non-secure, data links through communications satellites or ground networks. Where required, the airborne unit can operate independently of the ground stations, disseminating data via its communications systems. In this case, an airborne ASTOR crewman could simply relay, say, enemy positions to a commander on the ground by voice.

In addition to the radar mission, ASTOR has the ability to carry an EO-LOROPS (electro-optic long-range oblique photography system) and electronics support measures (ESM). The EO-LOROPS could be provided by such equipment as the DB110 digital camera, also used in the UK Tornado Raptor program.

ASTOR is due to enter service in 2005. The UK will have five aircraft and eight ground stations. ASTOR will be able to deploy at short notice in support of UK, NATO or United Nations operations.

According to George Robertson, UK Secretary of State for Defence, ASTOR "combines the operational advantages of the current American Joint-STARS system and those of the U2 surveillance aircraft. In terms of recent events in Kosovo, if ASTOR had been available, it would, of course, have been extremely useful. It can provide high-resolution imagery in all weather, and its stand-off range would have been beyond the reach of Serb air defense systems."

ASTOR has an advantage over Joint-STARS; it will operate at twice the altitude, thus providing a much larger radar footprint and better quality imagery.

Although ASTOR’s stand-off range is classified, it is known to provide sufficient distance from enemy forces to virtually preclude a surprise attack. The distance also provides protection, which is augmented on ASTOR by electronic counter measures (ECM). Operations in conjunction with the U.S. military’s Airborne Warning and Control System (AWACS) would increase its security still more.

Around the Track

The radar will have two modes of operation—moving target indication (MTI) and synthetic aperture radar (SAR). Two sub-modes of SAR will exist: "swath," which takes a broad view of the ground, and "spotlight," which provides a high resolution of a small area.

In a typical deployment, the aircraft will fly a racetrack pattern somewhere safely behind the forward line of troops. Radar imagery will be sent straight to the decision makers, whether they are at brigade, division or higher levels.

When it arrives on station, ASTOR’s first task, perhaps, would be to validate a map, in SAR swath mode. Although ASTOR acquires the image along a slant line, it can manipulate it to create a straight-down appearance. Even in swath mode, the resolution will be detailed enough to show oil refineries, rivers, ships, etc. The MTI mode will reveal moving vehicles. In Spotlight mode, a skilled interpreter can identify the vehicles—even detect such detail as to whether they have towing hitches or not.

ASTOR reportedly is a candidate for NATO’s Allied Ground Surveillance (AGS) requirement. However, ASTOR-loser Northrop Grumman is keen to rebound from its disappointment by winning the NATO contract with a version of its Joint-STARS. NATO is yet to decide on how large an aircraft it requires.

Meanwhile, in the UK, Raytheon estimates that ASTOR will sustain or create about 2,500 jobs, including about 100 jobs at Shorts, in Belfast, Northern Ireland, where the aircraft will be built. ASTOR’s main base will be RAF Waddington in Lincolnshire, and it will be operated and maintained by both Royal Air Force and Army personnel, with support from contract staff. About 350 service and 50 civilian posts will be created at the station, and up to 40 full-time contractor staff will be employed.

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