Thanks for your advice.
I will try to redo my AMM settings as soon as I come back home.
but I think I already managed to do all what you said since I had the same setting
1 msl fc Missile Fire Control FC237-R1 (40%) #1 (3v1 PD Mode 3600): No Target Assignment
Size 1 Missile Launcher #1 - Patriot (Ready To Fire)
or something very similar.
My problem is that this setting doesn't stay : if i check another ship and come back on the first one, it has disapeared.
I wonder if the fact that my AMM are much closer range than yours is relevant or not.
In fact, in my campaign, I have absolutly no scientist in sensor and fire control, so I completly suck at long range sensing of incoming missiles, so I decided to have AMM salvo launched at "close" range (2 millions km) with my manual assign method.
And the results are very poor : in fact, my gauss gun turrets (which don't need any target assignments nore any kind of setting to auto-fire at incoming missiles) do all the anti-missile defense job for me.