Christina Sierra is a supporting character in Kidou Senshi Gundam 00, serving as a bridge operator for the private military organization Celestial Being. She is calm, professional, and dependable, helping coordinate Gundam operations from the Ptolemaios. Christina plays an important support role in the series, contributing to mission control, communication, and ship operations. Her presence adds emotional grounding to the crew, and she is remembered as one of the more sympathetic and humanizing members of Celestial Being.