Yirbay (pronounced jɪərbeɪ) was a Soong-type android with the appearance of a humanoid female. She was employed by the Soong Foundation and worked as a lead researcher at the Noonian Soong Spire of Ktarn Fleet.
Meaning "Progress" in the native tongue of one of her developers, Yirbay was a second generation Soong Foundation android. After the restoration of the Data personality in the B-4 android, the Soong Foundation was able to use that research to further develop android technologies.
Some of that first group of androids entered Starfleet Academy while others joined the Soong Foundation and the Daystrom Institute. Yirbay chose to stay on with the Soong Foundation and their research.
At the Spire
In a research agreement with Starfleet, the Daystrom Institute and the Soong Foundation gained access to the Solanae Dyson Sphere. Some of their personnel, led by Yirbay, were assigned to work with Ktarn Fleet at the Soong Spire.
Yirbay would eventually become essential in unlocking many of the secrets of the Solanae spire and the work of her team would greatly assist Ktarn Fleet during the conflicts of the early 25th century.
Yirbay was a dedicated and persistent individual. She was known to work tirelessly on her projects, but also led her teams with a fair hand. The missing portion of her face was damage Yirbay received during an experiment gone awry. She chose not to replace the covering as a reminder to be careful in her work.