Cassini was a Federation Starfleet science officer in the late 24th century.

In June 2376, Ensign Cassini was assigned to the USS Defiant during its three month mission of exploration in the Gamma Quadrant. (DS9 - Mission Gamma novel: Twilight)

He brought with him a pair of self-heating slippers which he lost in a game of poker while on Vanimel. (DS9 - Mission Gamma novel: This Gray Spirit)