 On Titan launches, the Titan booster would launch the IUS, carrying the payload into low Earth orbit where it was separated from the Titan and ignited its first stage, which carried it into an elliptical "transfer" orbit to a higher altitude.On Shuttle launches, the orbiter's payload bay was opened, the IUS and its payload raised to a 50° angle, and released.After the Shuttle separated from the payload to a safe distance, the IUS first stage ignited and, as on a Titan booster mission, entered a "transfer orbit".