ADCO was an agency or title held by a Starfleet officer at Starfleet Command's Fleet Operations Center, Sol Sector.
In January of 2155, Starfleet officers J. Rudolph, J. Mees, M. Westmore, J. McMeikan, D. Curry, and M. Gullesserian were working in or as ADCO. It and the officers' names were listed on directory placards. (ENT: "Demons", directories)