UNSC Atlas
From Halopedia, the Halo wiki
The UNSC Atlas was a carrier in the UNSC fleet in 2525. On April of that year, the vessel went on patrol in the Lambda Serpentis System. Unbeknownst to most of the crew, the Spartans were aboard for this mission, to recover from their augmentations - and bury their dead - in the microgravity atmosphere.
The Atlas had a detatchment of ODSTs from the 105th Orbital Drop Shock Trooper Division. One morning, in the Atlas gym, an apparent training exercise between John and four ODSTs left two of the ODSTs dead. Unbeknownst to John, or apparently ONI for that matter, the Lieutenant in command of those four ODSTs was Antonio Silva, who would, as a Major, lead the ODST detatchment of the UNSC Pillar of Autumn.
