STEWART PENNEY / LONDON
First Airborne Stand-Off Radar scheduled for delivery to UK in third quarter 2004
Raytheon has modified the array for its Airborne Stand-Off Radar (ASTOR) ground surveillance aircraft by incorporating active array elements into the passive antenna system.
ASTOR is a synthetic aperture radar and moving target indicator sensor being developed for the UK's Ministry of Defence.
Peter Robbie, Raytheon Systems UK director of radar and reconnaissance systems, says: "We have distributed some active transmitter modules throughout the antenna to slightly change the power distribution."
A traditional antenna has a single high power transmitter; its active equivalent has an array of low-power transmit/receive modules. The advantage of a passive antenna is that it is lighter, cheaper and needs less cooling. BAE Systems will build the array.
Robbie says a hybrid passive/active antenna was offered to the MoD during the competition.
The benefits he says, is "that we're giving the radar more sources of power". He adds that "it increases reliability and helps with the system's growth potential".
Problems with development of the Lockheed Martin U-2's ASARS-2A radar - the ASTOR system is derived from ASARS - has not affected the programme, Robbie says.
The radar has passed its preliminary design review and is approaching its critical design review (CDR). The CDR encompasses a range of tests that will probably be concluded towards the end of the first quarter of next year.
Robbie says Bombardier's Global Express business jet test aircraft fitted with the ASTOR underfuselage canoe fairing and satellite communications radome has flown to 49,500ft (15,100m), proving the aircraft's ability to operate at the high altitudes required for long-range surveillance.
As well as the radomes the aircraft has been fitted with large delta fins under the rear fuselage and a fin-top extension to provide extra directional stability to counter the presence of the fairings. The satcom has also been moved back to reduce drag.
The first ASTOR is due to fly in October 2003, with initial delivery by third quarter of 2004.
Source: Flight International
