The 'UNSC Bright New day was a Paris-Class Heavy Frigate, constructed in 2516. Though a fairly unremarkable ship it saw action in dozens of battles over the course of the Human-Covenant War and destroyed a number of Covenant ships during this period.
During the initial assault on the planet, the Bright New Day had been part of the small defence fleet, made up of one Halcyon-Class Cruiser, the UNSC Konakli, and two other Frigates; the UNSC Troy, and the UNSC Starhood. The other three ships were destroyed, and the Captain, Uriah Maxon, ordered the ship to retreat, landing on the planet as an emergency evacuation point for the stranded UNSC forces. On the 14th of March, 2552, the remaining human forces boarded the Frigate, having been put into full retreat. Captain Maxon was convinced to wait for a few stragglers by Master Chief Petty Officer Fenn-145, who was unwilling to leave Jax-007 and several marine squads behind. Upon leaving the planet, the ship, now laden with survivors, was contacted by the Covenant Destroyer, Justicar. The Ship Master, Felo 'Ranakee, who was not actually on the ship at that time, had been wounded by Jax-007 and was on a Spirit Dropship. He wanted to exchange navigation data to the human homeworld for their lives. Fenn-145 and Lieutenant Martin Keel sacrificed themselves, detonating several nuclear warheads while inside the Destroyer, obliterating it. Shortly after, the Frigate left the Harpa system and travelled to Reach.
The Bright New Day did not play a major role in the Fall of Reach. As a matter of fact, it was decommissioned taken to the Aszod Shipbreaking Yards to be dismantled and destroyed. However, the planet was attacked, and the ship was left intact. On August 30th, 2552, the remnants of Spartan Teams Sigma, Tau and Upsilon, whom were fleeing the Covenant after the Battle for Outpost Foxtrot-Whiskey, arrived, attempting to escape Reach via the UNSC Pillar of Autumn. However, they missed it by minutes. However, upon finding Whiskey-04, an Elite ODST Squad, the Spartans discovered the Frigate, and after fending off Covenant forces, was able to lift off and escape Reach. In accordance with the Cole Protocol, the ship made several random jumps into Slipspace.
After picking up a distress signal from the colony world Hope, the Bright New Day travelled there, only to find it under attack by the Covenant. After a brief skirmish with a Covenant ship, the frigate's FTL drive was damaged, forcing it to land on Hope's surface. Sigma Team set out, leaving the ODST's and crew behind to take care of the ship, to find survivors and the materials needed for a repair. After a short battle in Port Neandra, and after ambushing a large Covenant patrol the Spartans were able to acquire an FTL drive from an undamaged ship stored in the Port Neandra Shipyards. The FTL Drive and Sigma Team were airlifted by Sergeant Major Richard Mack Junior and his team. At this time, Hope began to fall apart. After a lengthy chase, they were able to make it back to the frigate and install the FTL drive, giving them slipspace capability. The Bright New Day was able to escape to the edge of the system as Hope imploded.
Shortly after Hope's implosion, the UNSC Heavens Asunder, a small prowler vessel sent by ONI, arrived in the system, coming out of slipspace dangerously close to the frigate. After some investigation by the SPARTAN-II's of Sigma, the ship's only occupant was Commander Elena-071, someone who had been thought long dead by her comrades. Initiating 'Operation:ASPHALT', the Heavens Asunder jumped again, following the slipspace trail of another UNSC ship to an unknown planet. Shortly after, a message was sent to the Day from Marco-035, requesting assistance from the SPARTAN-III's onboard. The Frigate followed the prowler's trail to the planet, where it dropped of reinforcements for Sigma Team in the form of Martin-A136, Louie-A199 and Alex-A121, while Whiskey-04 waited on standby.
The Bright New Day and its crew arrived back on Earth on November 1st, 2552, only to find it under attack. Knowing that the ship would not last long against Truth's Fleet, he plotted it on a collision run with a Covenant carrier, while the Spartans and ODST's escaped in SOEIV's. The Bright New Day collided with the Covenant Ship destroying itself and the enemy ship in the progress.