All of them may be going for RF seekers based on whats available to them & what's also possible. The obvious problem is ranging with a passive seeker. That has significant problems with a missile that flies out a huge distance and hence cannot rely on mid-course updates alone to accurately judge & target a maneuvering target.
But IIR seeker equipped missiles at range or even multi-spectral ones are clearly the future. Either today, or tomorrow, they are coming, with exponential advances in datalinking infrared imagery. Even today, the PRC has cottoned onto it as well.https://www.popsci.com/china-new-long-r ... ir-missile
The VLRAAM's backup sensor is a infrared/electro-optical seeker that can identify and hone in on high-value targets like aerial tankers and airborne early warning and control (AEW&C) radar aircraft. The VLRAAM also uses lateral thrusters built into the rear for improving its terminal phase maneuverability when engaging agile targets like fighters.
Now, lets look at even the US, as cited below. We can have a 10 Mn word debate on this, but the obvious reason to go for such investments in IRST tech., is because the US is not too sure that even its AESA equipped fighters are that future proof against massive ERP jammers equipped with wide bandwidth DRFM.
As the conventional RF detection field gets crowded, the crowd will start eyeing the optical side, and then the real exotics which are still maturing in labs. The same applies for acquisition sensors on aircraft OR on their weapons.
We can't get into the FPA/MCT game fast enough. Sadly, funding.
In making a virtue out of a necessity, and replicating what PIRATE long claimed to a degree and what Rafale also likely does, we have:https://nationalinterest.org/blog/the-b ... inas-25964
As Gillian explained, while the IRST Block II is not part of the Block III program, the advanced processing, datalinks and sensor-fused display onboard the new Super Hornet variant enable the new capabilities envisioned for the new sensor. As Bob Kornegay, Boeing’s capture team leader for domestic F/A-18E/F and EA-18G programs, explains, the critical Common Tactical Picture sensor-fused display will be enabled by the Block III aircraft’s powerful high speed anti-jam TTNT datalink and the sheer computing power of the DTP-N processor, which is needed to run the complex algorithms that make multi-aircraft data-fusion possible.
What makes the new IRST particularly capable is that it operates in the long wave infrared band, which allows the sensor to passively detect and track targets well beyond the range of the APG-79 radar. “It can see a hot airplane,” Kornegay said. “It has much longer range—it is a long wave long range IRST—so it can see much further than radar can.”
Boeing has taken into account the traditional limitations of infrared sensors, where performance can be severely degraded by inclement weather—particular clouds and atmospheric moisture—when testing the new sensor, Kornegay said. The new IRST is so advanced that it still consistently generates tracks at extended ranges even taking into account inclement weather and other factors. “We’re not assuming a clear day,” Kornegay said.
A single Block III Super Hornet equipped with a Block II IRST would be able to detect and track a low observable enemy aircraft such a J-20 or Su-57 at extended ranges. However, that lone Block III jet would not be able to generate a weapons quality track on that enemy stealth aircraft because an infrared sensor cannot independently generate range data.
“If you have a single IRST ship, with your IRST, you can get a line of bearing—it’s going to see a hot spot out there, what direction it’s in, but it doesn’t have the distance. You don’t have a weapons quality track,” Kornegay said. “Now if you combine two aircraft, the fusion algorithm, now you have lines of bearing from two different sources. Where those two sources cross, the algorithm is going to compute a weapons quality track on that aircraft. So that’s a huge advantage for the warfighter to see that long before you’re in the enemy’s radar range.”
Indeed, as Gillian noted, the IRST is explicitly a counter-stealth development designed to defeat enemy low observable aircraft. “If the enemy aircraft coming at you is low radar cross section—low radar signature—it is still emitting a heat signature,” Kornegay said. “So it helps us as the enemies are starting to develop their stealth aircraft. It helps us to defeat that by moving outside of that X-band range.”
The U.S. Navy demonstrated the capability of the networked IRST, DTP-N and TTNT during the service’s Fleet Exercise 2017 onboard a pair of specially modified Super Hornets. The feedback from the naval aviators who flew during the exercise was that the capability was “eye-watering”—they were developing weapons quality tracks on targets that they had never seen before, Kornegay said.
Capt. David ‘DW’ Kindley, the Naval Air Systems Command’s (NAVAIR) F/A-18 and EA-18G Program Office (PMA-265) program manager, said that he could not talk about the specific types of platforms that the Navy practiced against during Fleet Exercise 2017. “Can’t talk about specific experiments and specific threats, but IRST is designed to be a long-range counter-stealth technology,” Kindley said.
Indeed, the Block I IRST was so effective during Fleet Exercise 2017 and other tests that the U.S. Air Force—which has traditionally been the Pentagon’s leading proponent of stealth technology—is planning on buying 130 of the pods for its Boeing F-15 Eagle fleet as a counter to emerging enemy stealth aircraft. Thus, ironically, the best counter to fifth-generation threats is a fourth-generation fighter equipped with new sensors and networking capability.