The payload canister transporter delivers its cargo lower left to Launch Pad 39B below the Rotating Service Structure.

Hours before dawn, the payload canister transporter delivers its cargo (lower left) to Launch Pad 39B, below the Rotating Service Structure (RSS). Inside the canister is the Chandra X-ray Observatory, primary payload on mission STS-93, scheduled to launch no earlier than July 20 aboard Space Shuttle Columbia (right). The canister will be lifted up to the Payload Changeout Room in the RSS where it will be relieved of its cargo. After the RSS rotates to a position behind Columbia, the observatory will then be installed vertically in the orbiter payload bay. The world's most powerful X-ray telescope, Chandra will allow scientists from around the world to see previously invisible black holes and high-temperature gas clouds, giving the observatory the potential to rewrite the books on the structure and evolution of our universe