Peräpäästä tietysti paistaa moottori / suihkuvirtaus. Mutta, etupäästä näkyvät ilman vastuksen takia lämpenevät etuosat ja johtoreunat.
http://aviationweek.com/awin/gripen-sensors-claim-counter-stealth-performance
he JAS 39E will have three Selex-ES sensors. The Raven ES-05 active, electronically scanned array radar (AESA), developed by the company's Edinburgh unit, will be the first production AESA to be mounted on a “repositioner,” a rotating mount that gives the radar a ±100-deg. field of view around the nose. The Skyward-G infrared search and track (IRST) system (from Nebbiano, Italy) is based on experience with the
Eurofighter Typhoon's Pirate IRST and Selex-developed land- and sea-based IRSTs. The fighter also has a new identification friend-or-foe (IFF) system with three electronically steerable antenna arrays, which matches the radar's range and field of view.
The three main sensors will cue one another automatically to display to pilots a fused picture of airspace around the fighter; it will also be fused with the JAS's new electronic-warfare system. Finally, sensor data can be shared between Gripens in a flight via data link.
The IRST is capable of detecting low-RCS targets at distances compatible with a beyond-visual-range missile launch, Mason says. “We have seen them,” he responds when asked if Selex IRSTs have tracked low-RCS targets. “We are looking at very small delta-Ts [temperature differences between the target and the background]. Some infrared absorbent paints cause more friction than standard surfaces, and that causes kinetic heating that the IRST will pick up.” Skyward-G does not depend on a supersonic target—
“skin heating at 300-400 knots is significant”—and detects heat radiating through the aircraft's skin from the engine, as well as skin friction and the exhaust plume.
Jos kiinnostaa, niin kannattaa lukea tämä hyvin ymmärrettävästi kirjoitettu opus:
TRENDS IN AIR-TO-AIR COMBAT
IMPLICATIONS FOR
FUTURE AIR SUPERIORITY
https://www.google.fi/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwikg7eM6JTLAhXKFJoKHSMcA_QQFggiMAE&url=http://csbaonline.org/wp-content/uploads/2015/04/Air-to-Air-Report-.pdf&usg=AFQjCNGuPkE3Fnei78vEdeXIqm-RbU3r4w&sig2=tuURE_KpC4i1br-m1IhLzQ&cad=rja
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