The Starfleet exploration class of the 2380s whose most famous member was William Riker's USS Titan.
The Luna-class was a Starfleet starship design of the 2380s, used for exploration. Its best-known member was the USS Titan, which William Riker commanded after leaving the Enterprise-E.
Under Riker the Titan came to the rescue of the USS Cerritos when the Pakleds attacked it in 2380, and the class remained a familiar sight in Starfleet. A later ship of the name, the USS Titan-A, was an entirely different and larger design.