From Halopedia, the Halo wiki
UNSC Marine Corps
Staff Sergeant Elena K. Bobrov (service number 91532-11116-EB) is a non-commissioned officer serving in the UNSC Marines that was assigned to the UNSC Infinity during the Battle of Requiem.
In July 2557, Bobrov was aboard the Infinity when the ship was caught by the gravity well of the shield world Requiem. She was later assigned to Gypsy Company to destroy the particle cannons that defended the gravity well generator. The Company was sent to the location of the particle cannons, designated "Sniper Alley", along with an M510 Mammoth. Bobrov was in charge of driving and controlling the Mammoth during the engagement.