The Intergalactic Travel Visa is a visa by law that ships that travel across the galaxy must have. If a ship does not have one, or has one that is expired, they are not allowed to travel across the galaxy. Although Zerard has a 3 day docking exceptance to those who don't have a valid visa card.
The Dorgenark has an expired Travel Visa card, so the Dorgenark docks at Zerard to renew their Travel Visa. Jaster, Lilika, and Simon are sent out to retrieve one.