Jump up into the air and press Guard. You will immediately jump out of the sky and the homing missiles will not hit you. This is also good against any mech (Virturoid) in the game, and especially against homing attacks such as Viper II's Homing Blast, Bal-Bas-Bow's homing explosives, and the Vr Raiden's Double Twin Lasers and Quadruple Standing Laser.