Multiple realities(covers information from several alternate timelines)
Dick D'Angelo was a Starfleet officer in the 24th century.
In 2353, he was listed as a Starfleet Operational Support Services officer on a directory placard in Starbase 32, Maxia sector. His office was located in room #75274. (TNG: "Violations", directory)
In 2367, he was a lieutenant aboard the USS Enterprise-D. According to the Engineering Division duty roster, he was an ops engineer for the Third Shift Antimatter Operations Unit. This roster was on display via the desktop monitor in the ready room. (TNG: "Suddenly Human", okudagram)
In 2371, he was a crewmember aboard the USS Voyager. He was among the crew stranded in the Delta Quadrant, when Voyager was forcefully brought there by the Caretaker. In that year, his name was listed on a crew manifest. (VOY: "Projections")
In 2372, he was listed on the Planetary Geosciences Division duty roster. (VOY: "Parturition")
In an unknown, alternate future timeframe, he was listed as a Tactical Systems officer on the dedication plaque of the USS Pasteur. (TNG: "All Good Things..." dedication plaque)
This character was only mentioned in writing.