Yes, the HARM missile is modelled as an anti-radiation (ESM sensor) missile. I have not checked the db thoroughly, but if there is a sensor created, then other real-world antiradiation missiles in the game could be modelled as well.
In terms of anti-ship missiles, none of these are anti-radiation missiles as far as I know. Light anti-ship missiles use IR like the Penguin, but generally speaking an anti-ship ASuW missile is a large fast or sea-skimming vampire, making an active radar seeker the best homing option.
In terms of evading an anti-ship missile, make sure you have your CIWS 20mm on AUTO in the Weapons Control station and an SM-2 missile loaded. Also, have your CM Autocrew engaged (bridge). When you get a vampire warning, fire your SM-2's at 'em! What don't die from the SAM's ell catch it from the vulcan!
Well, theoretically...
Actually, the generally consensus is that the OHP is toast from a barrage of Kitchen, Shipwreck, or 54E in RL, and some people think just one, or even half of one (
)...
I don't have much experience with OHP, so I'm not sure about tactics involving the radar and EMCON, Emission Control (radars off), but I'd imagine having the air search radar on would greatly improve your ability to respond to ASM missiles. In fact, you'd probably want to have both of your radar's on most of the time, since just about anything in the water, air, or on the sea will be able to detect you before you detect them. However, I'm sure a more experienced OHP commander could fill in here. :hmm: