Lieutenant DeLong was a Starfleet officer in the 24th century.
In 2367, DeLong was assigned to the Engineering Department of the USS Enterprise-D. When it became apparent that the entire system of power transfer conduits would be back online before the starship finished performing scheduled impulse maneuvers, DeLong ordered a Pre-Cervantes calibration of the antimatter injector modules by the third shift personnel. This action would help the department with a scheduled avitable alignment. (TNG-R: "Galaxy's Child")
This character was only mentioned in writing.
For the remastered edition of "Galaxy's Child", the original Okudagram was replaced by a new graphic. DeLong was mentioned in that graphic.