Federation vessels in the mid 24th century used for deep-space exploration and science used in 2370's.

Named after Greek mythology. A conjectural class, there isn't an entry for the Chimera-class in the Star Trek Encyclopedia.

USS Portland NCC-57418
   Searched for Odo and Garak in the Algira sector after their runabout became missing in 2371.
   "The Die is Cast" - DS9