Professor Ballard was a teacher at a university during the mid-24th century.
He had a daughter named Lyndsay, who was assigned to the USS Voyager. He had met Harry Kim on at least one occasion.
When Lyndsay died, and was turned into Jhet'leya by the Kobali, she couldn't remember her real father anymore. (VOY: "Ashes to Ashes")
This character was only mentioned in dialogue.