Candrea Thomas/NASA Launch Commentator: This is Shuttle Launch Control at T-3
hours and holding.
The countdown for launch of space shuttle Discovery's STS-119 mission is under way
here at NASA's Kennedy Space Center in Florida. Teams are monitoring a drop in helium
pressure in one of four liquid hydrogen gap measurement plates at the liquid umbilical
disconnect where the orbiter connects to the tank. The gap measurement plate maintains a
positive purge between the external tank and the orbiter interface to prevent potential ice
formation and keep the electrical equipment at the right temperature.
All four gap measurements are working, but one has dipped slightly below requirements.
The condition will be monitored but is not currently expected to impact tonight's launch.
Teams also are exploring the option of manually adjusting the ground systems valve in
the mobile launcher platform to assist in increasing the pressure.
We'll continue to provide updates on this potential issue as they become available.
Liftoff is scheduled for 7:43 p.m. Eastern time from Launch Pad 39A.
The launch window extends for about five minutes. This mission will deliver the S6 truss
segment and the fourth of final large set of solar array wings.
The arrays will provide 25 percent more power to the station and will fully power science
experiments and support the station's crew expansion to six residents in May.
There will be three spacewalks during this 13-day mission. Discovery also will take up
the Japan Aerospace Exploration Agency's first resident crew member Koichi Wakata
and bring back NASA astronaut Sandy Magnus, who's been living on station since the
STS-126 mission in November of 2008. STS-119 is the 125th space shuttle flight and the
28th flight to the station. It is the 36th flight for shuttle Discovery and the
first flight in 2009.
Discovery's crew of seven began their day this morning at 9 a.m. and have received
medical checks by the flight surgeon. In about 45 minutes the crew will begin putting on
their launch-and-entry suits before heading to the launch pad. At about 10:18 a.m. we
began operations to load the external tank with more than 500,000 gallons of liquid
propellants that will be used by the shuttle's three main engines to lift Discovery into
orbit. Managers and engineers are in Firing Room 4 in the Launch Control Center at
Kennedy Space Center in Florida monitoring the countdown. Tanking operations
generally last about three hours and were completed earlier this afternoon.