Yes, this specific topic is somewhat complex and can be broken up into multiple parts...
1. Pre-launch targeting;
2. post-launch mid-course updates;
3. a case of losing mid-course updates before weapon is active.
These may not always be 1-to-1 related to each other. Using AMRAAM as an example, but the same discussion would apply to any similar weapon. When an active radar guided missile (such as AMRAAM) is given its pre-launch targeting information, whether a radar tracking is required or not is not particularly a weapon limitation but that of launch platform interfacing the weapon. To my knowledge, most circa 2000 era users of AMRAAM do require an active radar track (such as STT or TWS designation) of target to give the missile its initial targeting information. The exception is a 'maddog' launch, in which the missile is fired without any targeting information whatsoever, goes immediately active and guides into first target the active seeker acquires. I understand that most A-to-A ARH missiles are capable of being launched this way.
I don't know the details of platform-to-AMRAAM interface communications, however, I would believe there are no fundamental technical reasons to not be able to target a missile to a target designated by other on-board sensors or fusion of sensors, or even one datalinked to a launch platform. I'd expect several up-to-date, circa 2020 era launch platforms to be able to do at least the former. I'd also expect similar capability from modern-day Russian (or other) platforms.
Now, after the launch, it is by default the launch platform that must provide the missile its mid-course updates of the target's changes. This will almost certainly make the launch platform somewhat vulnerable to detection in comparison to a case where it would remain with its radar completely silent. What makes an interesting aspect is what happens should the launch platform not give the missile any post-launch updates. To my knowledge, at least the major variants of AMRAAM should not go blind in a same way a SARH missile would, but should be capable of continuing with the last known target information. Noteworthy thing is that there reportedly are (were?) variants of AMRAAM that lack the mid-course update capability entirely; I don't see why the variants having such capability would be any dumber should they not receive the mid-course data (well, I can think of one reason, but anyway). Obviously, left alone the missile is less likely to readily acquire the target by the time it goes active, depending on the maneuvering of the intended target.
It would be interesting to find some details of the platform-to-weapon communications interfacing, but it is unlikely there are too much material in the public. Because the launch platforms in general do require radar tracking specifically, I suspect the AMRAAM cannot be targeted in "a target position only" way, or in bearing only (except for 'maddog') but at least an artificial estimate of target's position by the calculated time of impact is probably needed. I'd guess the target's speed is the key ingredient that is missing from a generic, 'raw' IRST targeting information.
< Message edited by AKar -- 2/22/2019 6:16:30 AM >