Angelo Tassoni was a crewmember aboard the USS Equinox under the command of Captain Rudolph Ransom in 2371. In that year, the Equinox was stranded in the Delta Quadrant by the alien entity known as the Caretaker.
Tassoni participated in criminal experiments to augment their warp drive by murdering a series of nucleogenic lifeforms and converting their remains into a source of fuel, presenting the crew with the opportunity to return to the Alpha Quadrant in mere months.
The Equinox crew hid their vessel in orbit of a planet with a parthogenic atmosphere, where Noah Lessing led a landing party of himself and Tassoni to localize deuterium ore deposits. While on the planet, however, the team was ambushed by a team from Voyager, and both were taken into custody.
After the death of Captain Ransom and the destruction of the Equinox, Tassoni was integrated into Voyager's crew along with four other Equinox crewmembers. As a consequence of his actions, he, alongside his fellow Equinox survivors, was stripped of rank, granted severely limited privileges, and ordered to serve under heavy supervision until he could re-earn Janeway's trust. (VOY: "Equinox", "Equinox, Part II")
Tassoni was played by stunt actor Brian Simpson who also played another officer in VOY: "Infinite Regress".
In the novelization of Equinox, this character was called Angela Tassoni, implying that the character was female.