Type-48 Artillery Platform

You may be looking for the related articles Anti-Aircraft Battery or Covenant Air Artillery The Covenant Artillery is a piece of ground-based Covenant field artillery. It fires bolts of plasma in indirect parabolic trajectories, and is essentially a larger version of the Plasma Mortar mounted on Type-25 Wraiths.

Halo 2 E3 Demo
The Covenant Artillery gun was first seen in the Halo 2 E3 Demo. When the Covenant invaded Mombasa, they stationed a handful of artillery pieces on the ground, which demolished UNSC buildings. Eventually, SPARTAN-117 and his group of Marines encountered one, and Sergeant Banks called in a Longsword air strike to destroy the stationary mortar. A sizable difference is that in the demo the Anti-Aircraft Battery is larger than its Halo 2 and Halo 3 successors.

Halo 2
The roles of the artillery guns as an active part of the Covenant assault were greatly downgraded in Halo 2, as the Earth levels featuring the guns were completely redesigned. Several artillery pieces were seen deployed on the beach of Old Mombasa in the level Outskirts, but none of them were seen firing during gameplay.

Trivia

 * The Covenant Locust in Halo Wars bears noticeable resemblance to the Halo 2 design of the AA battery.
 * In Halo 2, it is unknown whether the Covenant placed them as a deterrent or as an effective offensive weapon, since none are actually fired.
 * In Halo 2, if you mod the maps with the AA battery present, you can witness the intended projectile of the weapon. It is very similar to the E3 Demo projectile. This projectile looks exactly the same as a Wraith's Plasma Mortar shot, but has very high damage and an extremely large explosion radius, which is about twice that of the Scarab's main gun beam.
 * The versions of the Anti-Aircraft Batteries featured in the Halo 2 E3 Demo appear to be several times larger than the ones featured in the final version of the game. An explanation for this could be that Bungie did not want to scrap the model after rewriting the layout and storyline for the level Metropolis. As a result, Bungie downsized and reused the model for the level Outskirts in order to avoid having to scrap the battery's model which they had worked so hard to design.