A group of three turian officers can be found chatting inside Purgatory, in an alcove to the right of where James is located at the bar. Listen to their conversation to acquire the mission.
Scan the planet Digeris in the Castellus sector of the Apien Crest cluster. The Banner of the First Batallion is located there.
Completing this mission gives you 5 reputation, 15000 credits, and grants you the Turian Seventh Fleet War Asset.