Melbourne class

The Melbourne-class was a class of galactic survey cruiser that saw service in Starfleet during the 25th century. Its secondary hull was designed more like the secondary hulls were.

The prototype of the Melbourne-class was still in the planning stages in 2375. One of the study models were in Benjamin Sisko's ready room. 

However, due to internal wrangling among Starfleet, the Melbourne-class was not ready for production for over 40 years. The USS Melbourne (NCC-99247) was the lead ship of the class, still under construction as of 2415. It had more sensor equipment and more weapons than its predecessor, which rendered it capable of besting starships one-on-one.

Production notes
The length comes from a starship comparison chart of Federation science vessels and escorts in.