Space Commander was a rank within the Federation. Most notably, this was a rank held by Travis who after his direct appointment by Servalan to hunt Blake and his crew (TV: Seek-Locate-Destroy), directly reported to the Supreme Commander (TV: Project Avalon, Weapon).
Prior to this, Travis's role as Space Commander was being engaged in surface operations, including the ambush of Blake (TV: Seek-Locate-Destroy, AUDIO: Velandra) and direct involvement in fighting (TV: Trial).
Another Space Commander in charge of the attack on the Liberator with 20 plus pursuit ships. After the attack failed, Servalan ordered him to put himself under arrest (TV: Hostage).