At the Kennedy Space Center in Florida, technicians have started removing Discovery's three valves, two of which will undergo detailed inspection. Approximately 4,000 images of each valve will be reviewed for evidence of cracks. Valves that have flown fewer times will be installed in Discovery. Engineering teams also will complete analysis and testing to understand the consequences if a valve piece were to break off and strike pressurization lines between the shuttle and external fuel tank. Hardware modifications may be made to the pressurization lines to add extra protection in the unlikely event debris is released.

NASA and contractor teams have been working to identify what caused damage to a flow control valve on shuttle Endeavour during its November 2008 flight. Part of the main propulsion system, the valves channel gaseous hydrogen from the main engines to the external tank. After a thorough review of shuttle Discovery's readiness for flight on Feb. 20, NASA managers decided more understanding of the valve work was required before launching Discovery.

The Space Shuttle Program will hold a meeting March 4 to review new data and assess ongoing work. Managers then will determine whether to move forward with a flight readiness review March 6.

If Discovery’s tentative launch date holds, there will be no effect on the next two shuttle launches: STS-125 to NASA's Hubble Space Telescope and STS-127 to the International Space Station.