There seem to be a bunch of misconceptions around the IRIS-T missile.
So this is how the missile actually works in real life (make of it what you will):
This missile - the A2A variant like the SL variants - has a smart bicolor infra-red imaging warhead combined with an active K-band radar proximity fuse which is also used for communication via digital datalink.
So this missile receives (or to be precise it ‘can receive’) sporadic updates via K-band radar signals, and it also uses the K-band radar for the ’ active proximity fuse’.
In other words:
This missile is not just a ‘heat seeking missile’ (to be precise it’s not just an ‘infra red imaging missile with smart target recognition and verification’) and it is also not a ‘radar guided missile’ either, but it can be guided via datalink using K-band radar for digital communication.
So what does all this mean with respect to radar warner systems and missile approach warner systems?
- Well good luck figuring that out because it will all be highly classified.
But a few things can be stipulated:
- Naturally the missile does of course receive and does emit some type and some amount of K-band radar signals (that are more or less easy or difficult to detect), but it does NOT lock on to targets via radar. Whatever this may mean for the missile’s stealth aspects, ECM/EWR and the effectiveness of radar warner systems and missile approach warner systems.
- Any ground based or air based radars used to detect the target will of coursed also emit radar signals and as mentioned the datalink communications between missile and the launching unit will happen via k-band as well but will most certainly be done via a (more or less) precisely focused beam from launcher to missile that may or may not scatter towards the target. (Any modern AESA or PESA antenna array used for this can focus a beam more or less precisely).
So the radar signal used for communication between launcher and missile may almost certainly not be easily detectable, unless the detector or radar warner is positioned within the direction of focused beam.
Whatever these radars (probably networked and cooperating and located at several locations) that are tracking the missile’s target do and how each of their radar signals may change as they ‘lock on’ and increase precision is of course also all highly classified.
So whatever that may mean for each of the target’s specific actual real world radar warner systems and how it may or may not be able to detect a ‘radar lock’ is pretty much speculation at this point and with the (extremely sparse to nonexistent) level of publicly available information.
It will all depend on the specific type and model of radar warner system installed on an aircraft (or ground based or naval or whatever other unit) as well as the specific system’s (smart digital signal processing) capabilities.
I know the Eurofighter Typhoon for example has active millimeter-wave radar as one part of the Praetorian/ EuroDass defense suite, this active radar system can (more or less effectively) detect approaching objects including missiles that do not actively emit any radar themselves.
Another somewhat interesting feature around the IRIS-T missile that many people do not know, is that German Eurofighter Typhoons commonly do NOT have on bord (Pirate) IRST systems the way British and Spanish Eurofighters carry them. (As far as I know Germany currently only has a couple of the two seater Variant equipped with PIRATE IRST for training and testing purposes).
Instead (almost all of) the German Typhoons use the IRIS-T missile’s own warhead as Infra-Red-Search-and Track (IRST) system.
This means once the last IRIS-T missile is fired the German Typhoon will then be ‘blind’ in infra red (other than night-vision goggles pilots may wear).
By the way as a side note, what this also tells you the German Typhoons having “Raptor salad” for lunch in the famous Red Flag exercise must have carried at least one IRIS-T missile under their wings (at a minimum) in order for them to be able to lock on to the F-22, and they could certainly NOT have flown ‘clean’ without any missile as it is so often published.
Also know that the commonly published performance numbers for the Eurofighter Typhoon are in fact usually based on the Tranche 1 Typhoons in interceptor configuration armed with 6 missiles, 4 of which they carry on recessed low drag stations on the underside of the fuselage, 2 of which they carry under the wings.
This is probably because the Tranche 1 interceptor configuration is what the original government contracts were based around, and these data were therefore more or less publicly discussed by politicians, administrators and government employees in those countries’ national parliaments.
So many online arguments and discussions around the Typhoons performance stats compared to other jets carrying their weapons internally, like the F-22 or F-35 do, are usually flawed in the sense that (unlike the commonly discussed numbers for US made F-16s and F-18s) the Typhoons commonly published numbers are for an armed Typhoon jet carrying 6 missiles but no external fuel tanks (a loadout which only produces little more drag than a ‘clean’ and unarmed Typhoon jet does).