"Port Royal" and are the original cruisers for the navy's Linebacker Program (Milestone Phase I, II and III), which provided theater ballistic missile defense capability, as test platforms to detect, track, cue, intercept, and interact with other national assets to shoot down ICBMs. The vessel's Aegis and Standard Missile Tracking systems have been upgraded with "long range surveillance and track (LRS&T)", and the ships were outfitted to carry the modified SM-2 Block IVA TMD. As of 2009, "Port Royal" along with "Lake Erie" and were the only three s to be equipped for the Aegis Ballistic Missile Defense Program. "Port Royal" participated as a tracking ship during operation "Stellar Athena" FTM 12 on 22 June 2007 off Hawaii. "Port Royal"s role has been taken by .