The arrival roster at Deep Space 9 listing Capt. Sondheim
S. Sondheim was a starship captain in the 24th century. He was the commander of the USGS Powell.
In 2370, he was listed on the Deep Space 9 arrival roster. (DS9: "Whispers", production art)
His name was not mentioned in dialog, it was simply listed in an okudagram graphic of an arrival roster on a viewscreen. The graphic was also populated by a number of other in-jokes. He was presumably named after composer Stephen Sondheim, given the nearby presence of Captain "H. Prince".