Spaceflight

At Kennedy Space Center's (KSC) launch pad 39B Space Shuttle Discovery’s countdown is on a hold expected to last until at least 1935GMT as final Orbiter systems and weather checks are made.

At 1935 NASA could restart the countdown and take it down to 5min, if a short final countdown is needed for an opportunistic launch at 1944 and 40s, the very beginning of the launch window.

Otherwise the 9min countdown would restart at 1939 for a 1948 launch, which is the optimum time to go to reach the International Space Station with the propellant Discovery has onboard.

Discovery’s hatch has been closed and the failed thruster heater issue has been closed by the mission management team (MMT).

While the launch team and MMT discuss the situation during the hold the weather is being monitored by two aircraft.

The NASA Shuttle Training Aircraft is flying on approaches to the KSC runway checking weather conditions in the immediate vicinity while a Northrop Grumman T-38 flies a much wider route for the local area.

The weather is currently the only issue that could stop the launch.

STS-121/Discovery is the eighteenth US mission to the ISS and the 32nd flight for Discovery.

The mission commander is Steven Lindsey and his crew of five NASA astronauts comprises, pilot Mark Kelly, mission specialists Michael Fossum, Lisa Nowak, Stephanie Wilson and British born Piers Sellers; and European Space Agency astronaut Thomas Reiter joins them to be transported to the space station to become the third member of the current ISS Expedition 13.

This second return to flight mission will see supplies delivered, replacement of a pump and a communication umbilical reel assembly for the ISS’s mobile transporter fitted, and Shuttle thermal protection system tile repair techniques tested.