NASA announced today July 1 to 19 is the new launch planning window for Space Shuttle Discovery's mission, designated STS-121. The new window gives the agency time to do additional engineering work and analysis to ensure a safe flight for Discovery and its crew.

Space Shuttle Program Manager Wayne Hale made the announcement during a news conference from NASA's Johnson Space Center in Houston. The decision to target July followed a two-day meeting on the external fuel tank's engine cutoff, or ECO, sensors. The sensors indicate whether the tank still has fuel during liftoff. During testing, one of the four ECO sensors had a slightly different reading than is expected. Shuttle officials have decided they will remove and replace all four liquid hydrogen sensors.

"We've been saying for months that our engineering work would determine when we fly our next mission. Targeting July is the right choice in order to make smart decisions," said Bill Gerstenmaier, NASA associate administrator for Space Operations.

Other issues factored into the decision to adjust the STS-121 planning window.

- Testing and analysis are required on the space shuttle's modified external tank. The testing will help verify that the tank is safe to fly without the protuberance air load, or PAL, foam ramp. The PAL ramp was removed after a large piece of foam fell from that area during shuttle Discovery's July 2005 launch. Also, more analysis is needed to decide whether changes are needed on the tank's ice frost foam ramps.

- Repair work on the shuttle's robotic arm must be completed. Space shuttle technicians on a work platform device accidentally bumped the arm last week, causing a tiny crack. The arm will be removed for repair.

The STS-121 mission will take Shuttle Commander Steve Lindsey and six crew members to the International Space Station. This is the second mission in the Return to Flight sequence to evaluate new heat shield inspection and repair techniques and to deliver supplies and equipment to the station