Since none of the elements are physically connected before they meet on orbit, a Digital pre-Assembly (DPA) is conducted during processing to discover any physical incompatibilities. Computer models of each physical interface are constructed, then these digital models are brought together. Any conflicts that appear can then be safely resolved before the elements reach orbit.
Astronaut crew members are also given an opportunity to participate in "hands-on" testing to prepare them for their individual missions. Multi-Element testing (MEIT) provides an opportunity for engineers and technicians to modify or correct deficiencies while the hardware is accessible on the ground.
Once the hardware has satisfied all test requirements, it is ready to be loaded into the Shuttle's payload bay. It is carefully packed into the payload canister, a large container with an interior identical in size and dimensions to the Shuttle's payload bay. The payload canister is then driven slowly across Kennedy Space Center to the Shuttle. Payloads can be installed in the Orbiter either at the launch pad or in the Orbiter Processing Facility.
At the pad, once the launch package has been installed in the Orbiter's payload bay, real-time test data is transmitted from the pad to the SSPF User Room to verify that the payload is working properly. The payload bay doors are then closed, and the hardware is ready for flight.