Disc MOAs are a variant of the MOA initially released on Update 28.0 (2020-06-11) with the Corpus Ship remaster. As of Update 29.10 (2021-03-19), each of the Corpus Proxima regions have their own models.
The Juno models fire small energy orbs that can ricochet off of surfaces once. The projectiles will dissipate on either the second collision or on contact with a target.
The Taro, Axio, Vorac, and Orm models fire simple fast moving disc projectiles.