The Mirror is an insidious enemy that uses its energy shield to repel your bullets. Depending on the hit angle it may reflect the bullets in your direction and damage you, so take care when shooting a mirror down.

Tips
-The mirror shield is disabled when its shooting you, take this chance to shoot it down.
-Also, you can destroy the 4 satellites creating the mirror shield, disabling it permanently and providing you an easy coreshot to the its main body inner core.