http://www.spaceflightnow.com/shuttle/sts121/status.html
1853 GMT (2:53 p.m. EDT)
The Orbiter Closeout Crew is departing the pad.
1850 GMT (2:50 p.m. EDT)
The Main Propulsion System helium system is being reconfigured by pilot Mark Kelly. Soon the gaseous nitrogen purge to the aft skirts of the solid rocket boosters will be started.
1853 GMT (2:53 p.m. EDT)
The Orbiter Closeout Crew is departing the pad.
1850 GMT (2:50 p.m. EDT)
The Main Propulsion System helium system is being reconfigured by pilot Mark Kelly. Soon the gaseous nitrogen purge to the aft skirts of the solid rocket boosters will be started.