The Aeolus-class frigate was a family of light frigate classes in service with the UNSC Navy. With three similar but separate subclasses based on a shared hull, the aim of the Aeolus-class was to provide a broad range of functions with three differing variants, whilst sharing parts, design costs and infrastructure and maintaining a greater degree of inter-operability than separate classes would allow. Multiple subclasses was not initially planned, however, with the class entering service in 2544 as simply the Aeolus-class frigate; subsequent subclasses would recieve II and III designations. The Aeolus I-class frigate was operated as a standard light frigate, participating in predominantly in patrol and pursuit in remote regions and operating alongside warships of heavier tonnage in larger scale action. The Aeolus II, introduced in 2556, was a heavily modified stealth vessel with an emphasis on electronic intelligence and surveillance, and covert insertion of ODST personnel. The Aeolus III, which entered service in 2559, was based on a modified Aeolus I hull and specialised in amphibious operations, expeditionary warfare and providing close air support to deployed ground forces.
Aeolus I-class frigate
The Aeolus I-class frigate, initially simply known as the Aeolus-class, was the first conceived of the three variants. Originally no variants were planned, and the vessel was destined to operate as a standalone light frigate class, but operational experience quickly indicated the viability of a stealth variant, and later, a variant tailored for atmospheric support. The success of these variants was a testament to the efficiency and versatility of the original design; while not being as well armed as the Charon-class frigate, the Aeolus was similarly well armoured and signficantly faster and more agile. The Aeolus was originally designed solely for patrol of remote areas and skirmishes with light, fast pirate and insurrectionist vessels, as well as the lightest of Covenant craft such as the Banshee-class starfighter; a role in which its light but versatile armament and rapid speed would suit it perfectly. However, as a result of its excellent combat performance, being able to outperform ships significantly stronger than it was designed to, the Aeolus was also applied to direct fleet action against Covenant forces. This proved vital to the UNSC as often defence was organised hastily, with no time to give consideration to a ship's roles making it unsuitable for direct action.
Commonly referred to mistakenly as a dedicated stealth frigate, the Aeolus II's role and function encompassed far more than a stealth capability, although this was a crucial part of its operation. The Aeolus II was a specialised warship utilised to provide a set of highly specific functions to a battle group. These included reconnaissance, electronic intelligence and surveillance, electronic support including command, control and communications, and anti-prowler/anti-stealth warfare. These functions made it highly valuable when deployed as part of a battle group, as it was able to actively supplement the systems and capabilities of other battle group components; however this also meant its ability in combat without such support was restricted.
While the Aeolus II had a limited combat ability when deployed without a battle group, it routinely performed non-combat operations, such as electronic intelligence gathering and reconnaissance, independently of the unit it was part of. Vessels of the subclass featured enhanced stealth features and countermeasures, in addition to strong shielding and high velocity typical of a light frigate, in order to increase effectiveness and survivability. A major role of the Aeolus-II was to covertly insert Orbital Drop Shock Troopers to a target using SOEIV pods, often in preparation for a full scale assault by UNSC forces.
The UNSC Arcady, an Aeolus II-class frigate, is destroyed in 2604.
Another imperative role performed by the Aeolus II was command and control of prowler units. The frigate could keep pace with prowlers and remain at a similar level of undetectability, whilst having better endurance and armament and an expanded communications suite. This allowed the Aeolus II to function as a control and coordination vessel to deployed prowlers in order to coordinate efforts. The vessel also had the ability to replenish prowlers while underway. In order to accomplish its unique roles, the Aeolus II was the most drastically altered of the subclasses, with an external hull altered to minimise RADAR cross-section. The ship's interior was similarly heavily modified to accommodate large quantities of electronic and sensory equipment.
Aeolus III-class frigate
A prototype Aeolus III-class frigate being refitted.