SURPIC may or may not have been available from an MPA via HF. If not the lead Buccaneer had to put his radar on and declare a range and bearing to his selected target. Additionally the missiles could be programmed from the cockpit to attack the nearest / furthest/ leftmost/ rightmost/ largest radar contact within its search ambit.
if SURPIC or VASTAC was available the missiles could be launched without radar transmissions and the first warning for the ships would be when the missiles pulled up and put their own radars on.