More than 400 hours of the crew's time will be dedicated to the USML-2 experiments. The seven-member crew onboard Columbia will work dual 12-hour shifts which allows the experiment operations to continue around the clock in the "shirt-sleeve" microgravity environment of the Spacelab module. Microgravity is approximately one millionth the gravity experienced on Earth, made possible in low Earth orbit by a condition known as freefall. Freefall provides the microgravity environment for the occupants and experiments onboard as the Shuttle falls around the Earth in such a way that it stays the same height above ground.
Pa yload Specialist Sacco activated two instruments which will determine what effect crew movements, equipment operations and Shuttle maneuvers can have on sensitive USML-2 experiments. The Space Acceleration Measurement System collects data for post-mission evaluation, while the Three Dimensional Microgravity Accelerometer collects acceleration data for both post mission and real time data analysis. Armed with data collected by these instruments, scientists can make changes to their experiments to compensate for on- orbit disturbances, thus utilizing their microgravity time to the fullest.