If you want to launch a SAM from a sub you first need to find whatever it is you want to shoot at. And if you radiate you're dead, you're limited to passive detection. And you have to stick something up to do that with--and the AWACS can see you from much farther away than you can see it.
The one thing that strikes me as a realistic threat would be to put up only a tiny antenna that can detect the radar of the AWACS. If you think it's in range you fire something like the AIM-120 on the line of bearing, radiation-seeking and then switch to it's active seeker when the target goes dark (as it almost certainly will if it thinks there's a radiation-homer out there.) They are slow, lumbering beasts that probably can't get out of acquisition range before the seeker goes active.
You still have the problem that you just left a flaming streak pointed right at you, a suicide move if you're anywhere near the fleet. It would make deploying an AWACS far from the fleet a bad idea, though. (Back with the old Harpoon wargame I found by far the best strategy was to station an AWACS a few hundred miles from the fleet in the general direction of the enemy. Russia had nothing with air-to-air weapons and the legs to engage it. It wouldn't be as effective against a competent enemy but it would still take a big bite out of maximum range by forcing the attackers to take a big detour around it.)
I also wonder how well an AWACS might be able to defend itself with it's radar. What happens to the seeker if the AWACS focuses it's radar on the missile?
Locate AWACS from ground/air/space sensors. (they're radiating like hell)
Communicate target location to sub via low-freq.
Sub transits to location. (realistically, would already need to be nearby)
Sub deploys canister. (have ICBM-dimensions to work with)
Canister hangs out just under surface, with surface communications buoy. Registers itself onto the fires network with LPI comms. ("I'm at XY cords w/ Z weapon", ACK)
Other assets then send order to fire when appropriate, w/ sufficient track. (since weapon is active, it just needs navigational track before it goes active)
Ideally, it's IR-guided, so AWACS doesn't get any lock warning.
Given SLBMs can toss a nuclear warhead at range, I expect they'd at least be able to loft several LREW / AIM-174 / AIM-260 class weapons to engagement altitude/speed. (~130,000 lbs vs 2,000 lbs)
The one thing that strikes me as a realistic threat would be to put up only a tiny antenna that can detect the radar of the AWACS. If you think it's in range you fire something like the AIM-120 on the line of bearing, radiation-seeking and then switch to it's active seeker when the target goes dark (as it almost certainly will if it thinks there's a radiation-homer out there.) They are slow, lumbering beasts that probably can't get out of acquisition range before the seeker goes active.
You still have the problem that you just left a flaming streak pointed right at you, a suicide move if you're anywhere near the fleet. It would make deploying an AWACS far from the fleet a bad idea, though. (Back with the old Harpoon wargame I found by far the best strategy was to station an AWACS a few hundred miles from the fleet in the general direction of the enemy. Russia had nothing with air-to-air weapons and the legs to engage it. It wouldn't be as effective against a competent enemy but it would still take a big bite out of maximum range by forcing the attackers to take a big detour around it.)
I also wonder how well an AWACS might be able to defend itself with it's radar. What happens to the seeker if the AWACS focuses it's radar on the missile?