Site Omega is a surface platform that's a part of PATHOS-II, being it's sole surface-built surface. It served as the weather and communication station of PATHOS-II.
The site's purpose was to function as the main communication and weather broadcasting relay for PATHOS-II, with one of it's functions being generating and broadcasting feedback messages over the success of each launch performed by the Omega Space Gun. It was unmanned, being occasionally visited by the MS CURIE for maintenance.
While it is not seen or explored by Simon Jarrett in-game, various bits of information on Omega such as maps and other paraphernalia can be found within the main underwater stations. Simon can also find audio recordings from staff members mentioning Omega, and is able to set routes to the site while in the Shuttle Transport.
Item #4540 provides insight about the station, describing it as "like a small oil rig, fitted with work rooms, a weather station, a couple of offices and a small habitat with beds and a kitchen" and confirms it has survived the Impact Event.
Behind the Scenes
All featured complexes in the game are named after a letter of the Greek alphabet; Omega is the twenty-fourth and last letter, in reference to how Omega is technically the final site as it is connected to the Omega Space Gun, which marks the end of PATHOS-II.