From Halopedia, the Halo wiki
In October 2552, it was stationed at Earth with the Home Fleet during the Battle of Earth. The Redoubtable descended near New Mombasa to aid UNSC forces in the battle taking place there. It was one of four ships fast enough and close enough to follow the UNSC In Amber Clad and the High Prophet of Regret's CAS-class assault carrier, Solemn Penance, into slipspace. The Redoubtable, as well as the UNSC Paris and the UNSC Coral Sea, was faster than the UNSC Dusk and sped out of the prowler's sensor range while in slipspace.
While the fate of the Paris is unknown, Coral Sea and the frigate were present towards the end of the Battle of Installation 05, during which Redoubtable, Coral Sea, and a number of other human ships conducted scans of the Halo’s surface. Redoubtable picked up a unique sequence emanating from the ring’s internal systems, which would eventually be cracked by acclaimed scientist Luther Mann in his studies on Forerunner numbering.
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