The threat that is driving Block III and IRST has not been identified, but China analyst Richard Fisher of the International Assessment and Strategy Center points to Chinese advances in X-band active, electronically scanned array (AESA) radars, which are able to be used as very powerful jammers. A large group of incoming aircraft jamming at megawatt power levels could make radar use challenging, he says.
Other air forces are farther down this road. “The U.K. went with IRST, Meteor and Asraam (AIM-132 Advanced-Short-Range AAM) on Typhoon for this very reason (intense jamming),” comments a British industry executive and former RAF fighter planner. MBDA's Asraam is not unlike the Block III concept. Its Raytheon-designed seeker is related to that of the AIM-9X, and it has a considerably larger motor.
The performance of the Typhoon's Pirate IRST has increased due to better processing and software since it entered service in 2007, says a Eurofighter engineer. The service-entry standard was “pretty raw.” Better processing exploits the fact that the IRST is extremely agile, capable of performing complex tailored scans, because its steering mirror is much lighter than a radar dish. It can scan faster than an AESA, in some cases, because it does not transmit. “The angular and thermal accuracy provides the processor with enough data to analyze the core and the edges” of objects in the field of view, the engineer says. “It's like a fingerprint.”
This is key to IRST performance, because as a passive system it provides no time-based range data, and has been historically susceptible to false alarms from stars, cloud reflections and ground targets. Better processing and fbriast scanning also make it possible to use geometrical techniques for range measurement.
The updated Pirate is believed to have shown its ability to detect the F-22 at significant ranges in 2010, when four of the stealth fighters were deployed to Lakenheath AFB in the U.K., according to European industry sources. Selex leads the EuroFirst consortium that produces Pirate, and its Skyward-G for the Saab JAS 39E Gripen uses similar technology.
The Super Hornet IRST mates a new processor to the sensor of the AAS-42, which was developed in the 1980s for the Grumman F-14D. It has already been supplied to export F-15 operators, including South Korea and Singapore, and is under contract for Saudi Arabia's new and upgraded F-15s.