From Halopedia, the Halo wiki
The UNSC Andraste was a UNSC Navy vessel attached to the UNSC Home Fleet, featured in concept art for Halo 3. Concept art for this vessel was shown in the book Art of Halo 3, as an early concept of what would evolve into the frigate UNSC Forward Unto Dawn. The name is a reference to Andraste, a Celtic war goddess.
Class and development
It appears that during the development of Halo 3, the Andraste underwent a change from corvette into a frigate. The Art of Halo 3 refers to the ship as a corvette, and the Andraste's hull classification symbol as seen in concept art is K-201; 'K' was once a United States Navy hull classification for a corvette but has since been retired.
However, the design of the ship is unmistakably similar to a UNSC frigate; it is possible that at the point when that particular image was made, the ship had already been established as a frigate. In addition, Isaac Hannaford, the artist who produced the image in question, identifies the ship as a UNSC frigate in his concept art blog.
Due to its hull classification sharing the same number as the UNSC Forward Unto Dawn (201), it is likely that the ship was replaced by the Forward Unto Dawn in the game, and that the "K" in the hull classification symbol in the concept art was a remnant from an earlier point in development when the ship was still to be a corvette.
The frigates in Halo 3 differ from the Andraste's design in a variety of ways, including a larger underside hangar. This change may have been made due to story necessities; including a scene in The Ark where the Forward Unto Dawn lowers multiple armored vehicles from its hangar, and in the end of the level Halo, where players must use a Warthog to jump into the open hangar. However, the design was more closely adapted to the Paris-class heavy frigates in Halo: Reach.
List of appearances