Asst. CEO
From Star Trek : Freedom's Wiki
The Assistant Chief Engineering Officer is an officer underneath the Chief Engineer. They operate by helping the Chief of the department by managing task on a day to day or lower level. A department may have many assistants because each assistant may have a team within the department (i.e., alpha shift, beta shift etc.) They also have many similar responsibilities of the Chief Engineering Officer when the Chief Engineering Officer is off ship or off duty.