EADS flight tests Typhoon AESA radar
Initial flight tests with an active electronically scanned array (AESA) radar designed to equip the German-Italian-Spanish-UK Eurofighter Typhoon fighter aircraft have been successful, EADS Defence Electronics (Ulm, Germany) said at the ILA 2006 air show in Berlin.
Flight trials in a real Typhoon are now anticipated to take place possibly later in 2006, depending on Eurofighter test aircraft availability.
The tests, held earlier this year -- using a BAC One-Eleven flying testbed aircraft -- at Bournemouth, southern England, involved the prototype of a future electronically scanning Captor-E derivative of the mechanically scanning Captor radar that is currently in production for the Typhoon Tranche 2 aircraft, said Dr Elmar Compans, head of the company's sensors department.
The prototype is known as CAESAR (Captor AESA Radar) and features an array with a classified number (between 1,000-2,000) of transmit/receive (T/R) modules. Its diameter is "slightly larger" than the mechanically scanned antenna that is now on Captor.
CAESAR has been developed since April 2002 by the four-country Euroradar consortium, led by Selex in the UK and including EADS Defence & Security in Germany; Galileo Avionica in Italy; and Indra in Spain.
Compans described the current mechanically scanning Typhoon radar, which he referred to as "Captor-M", as a "high-end multifunction X-band (10 GHz) pulse-Doppler radar with a modular architecture and more than 30 operational modes for air-to-air and air-to-ground operations". The radar, developed and produced by Euroradar (and delivered to BAE Systems in Warton, England), has a high resistance against electronic countermeasures and multitarget capability including track-while-scan, he said.
Scanning, however, is done by mechanically pointing the radar's antenna, which means that "a lot of time is wasted moving the antenna so that relatively little time can be spent on analysing targets", Compans added, "particularly if several targets spread out in space have to be tracked.
"By moving to an AESA radar, featuring an array packed with many hundreds of independently controlled [T/R] modules, it would become possible to do zero- delay switching between differ- ent look-angles
of the antenna, greatly enhancing the track-while-scan process."
Another advantage is the ability to introduce adaptive power management, which means that the radar's computer uses no more transmitting power than is needed to obtain the required information for each individual target -- resulting in a reduced probability that hostile forces can intercept the radar's signals.
Furthermore, the large number of T/R modules means that an AESA radar is not immediately in trouble if components start to fail, a process known as graceful degradation. "Performance degradation becomes
visible only after about 10 per cent of the T/R modules become extinct; you can lose around 100 before you have to cancel the mission," Compans explained.
In the fully developed version, a future Captor-E radar features multichannel signal processing and space-time adaptive processing, allowing the radar to distinguish between a moving target on the
ground and the ground clutter (ground moving target indication -- GMTI). The radar is also capable of adaptive beamforming, which includes the generation of multiple independent beams by dividing up the AESA array into sub-arrays. This is useful for jammer suppression.
According to Compans, an AESA fighter radar such as Captor-E will be able to simultaneously perform search, track, datalink, synthetic aperture radar imaging and other functions.
CAESAR was started in 2002 as a Euroradar-funded technology- demonstrator project. It was backed by a bilateral German-UK Captor radar e-scan risk-reduction project known as CECAR, which started in 2003.
According to Compans, CAESAR and CECAR objectives are to:
· perform experimental flight trials to demonstrate the feasibility of e-scan technology and its potential operational benefits;
· make maximum use of existing Captor radar subsystems;
· gathering data on the performance of the AESA array placed inside the standard Captor radome so that the radar's air-to-air radar modes could be optimised;
· de-risking the possible development and integration of an e-scan radar by identifying critical integration issues early on; and
· demonstrating the e-scan radar capabilities of the four Euroradar companies.
"The concept for CAESAR was to take the existing Captor radar; to replace its mechanically scanned antenna with the new AESA array, and to leave the whole of the back-end as it is, with the exception of
the antenna control unit and the antenna power supply unit. All Eurofighter avionics also remain unchanged. In terms of the new array there are no weight or centre of gravity issues that the aircraft cannot deal with.
"We believe that this evolutionary approach toward introducing an AESA radar on board Typhoon is the only way that it will be affordable for the customers." However, the proposed Captor-E is still expected to be more expensive than the standard Captor-M, Compans admitted. "It will certainly not be a factor two more expensive, but it will not be factor one," he said.
The SMTRM T/R modules in the CAESAR prototype are based on expertise gathered by EADS Defence Electronics in several other programmes, including the French-German-UK AMSAR fighter radar technology
programme, the SOSTAR-X airborne ground surveillance radar programme, the MEADS air-defence radar, the TERRA-SAR space-based radar and the BÜR next-generation ground-surveillance radar.
The standardised modular T/R modules (known as SMTRMs, size 64.4x13.5x4.5 mm) for CAESAR were completed by EADS Defence Electronics in April 2004, after which integration of the AESA array plus ground and environmental tests started in Ulm in July 2004.
Around that time, EADS also performed a fit check using a German Eurofighter at Manching, Germany, to verify that the CAESAR array would actually fit with the mechanical interfaces and the radome. In May 2005, the array was shipped to Selex in the UK where it was integrated with the rest of the radar.
In September 2005, the first transmission test of the complete CAESAR system was done, followed by: system integration in November 2005, installation on the BAC One-Eleven flying testbed aircraft at FR
Aviation in Bournemouth in December 2005/January 2006 and flight tests starting on 24 February 2006.
The flight-test campaign involved seven missions during which a total of 50 test runs were made over Wiltshire county in the southwest of England. "The AESA array operated successfully for more than 20 hours within one single T/R module failure," Compans stated. For the campaign, two aircraft were available to fly co-operative target profiles (these were an Alpha Jet A jet trainer and a Hawker Siddeley 748 twin-turboprop aircraft). "These targets were detected and tracked, including during crossing and weaving manoeuvres, while it was also possible to distinguish between them when they were flying
in close formation," said Compans.
"Various targets of opportunity were also detected and tracked. Data recording was successful and we have demonstrated track revisiting [looking back at targets detected earlier]. For cost reasons, the
CAESAR array was not fully populated with T/R modules, but approximately 75 per cent." The flight tests on the BAC One-Eleven involved the radar operating at "limited range but still representative of the full-up system". The AESA array's datalink capability was not included.
According to Compans, the CAESAR and CECAR projects have opened the door to full-scale development of the Captor-E radar for Typhoon Tranche 3, deliveries of which are scheduled to start in 2012. "That
means the radar deliveries are to start in 2011, and that means that there is less than six years left for development, industrialisation and production. We propose to use the existing back-end of the Captor
as is used in Tranche 2, as this is basically e-scan ready. The AESA array and the new LRUs [line-replacable units] are to be inserted in a plug-and-play fashion while the main avionics software would also not need to be changed.
"The intention is that the first production Captor-E sets should have the same functionalities that are now available in the Tranche 2 variant. Some easily implemented 'low hanging fruits' may also be added, but more difficult new capabilities will probably be introduced later as part of the radar's growth path."
In case the Tranche 3 aircraft are not built (Compans stressed that the contract for them has been signed), the Captor-E radar could be retrofitted into the fleet of Tranche 2 aircraft.
"The next step now is to perform CAESAR flight tests on board a real Typhoon aircraft, the main goal being to check out the radar's features in relation with the overall weapons system. There is no date fixed for this yet, but I would be disappointed if it did not take place during 2006," Compans said. He could not say at which location the Typhoon AESA flight trials will happen, but added that he "would be happy with any location as long as it happens".
Euroradar completed deliveries of Captor radars for Eurofighter Typhoon Tranche 1 at the beginning of 2006. The Tranche 1 version of Captor cannot be readily converted to an AESA radar because it features older, less performant processing technology. The Tranche 2 Captor radar that is now in production has the latest processing equipment and features a high-resolution ground-mapping mode that is not available in Tranche 1.