ADCO was a department, division, or position within Starfleet's Fleet Operations Center on Earth.
In January of 2155, Starfleet officers J. Rudolph, J. Mees, M. Westmore, J. McMeikan, D. Curry, and M. Gullesserian worked in (or as) ADCO. (ENT: "Demons" set artwork)
ADCO was seen on directory listings seen on the set of "Demons".
, like many of the other divisions, departments, or positions on the listing, is a reference to NASA
terminology, in this case, the "Attitude Determination and Control Officer".