From Halopedia, the Halo wiki
The Stasis Cannon is a Covenant stasis weapon found on the Vampire's frontal section. When fired, it disables the targeted enemy aircraft, rendering it unable to move or fire. Once the Vampire is upgraded with Stasis Drain, the weapon not only stops its target, but also drains its energy regenerating the Vampire itself and making the hostile crash onto the ground. Its second upgrade, Stasis Bomb, causes drained aircraft to explode, inflicting Area Of Effect damage.