WEBVTT

00:00:00.000 --> 00:00:03.000
Candrea Thomas/NASA Launch Commentator: This is Shuttle Launch Control at T-3

00:00:03.000 --> 00:00:05.000
hours and holding.

00:00:05.000 --> 00:00:10.000
The countdown for launch of space shuttle Discovery's STS-119 mission is under way

00:00:10.000 --> 00:00:15.000
here at NASA's Kennedy Space Center in Florida. Teams are monitoring a drop in helium

00:00:15.000 --> 00:00:20.000
pressure in one of four liquid hydrogen gap measurement plates at the liquid umbilical

00:00:20.000 --> 00:00:25.000
disconnect where the orbiter connects to the tank. The gap measurement plate maintains a

00:00:25.000 --> 00:00:30.000
positive purge between the external tank and the orbiter interface to prevent potential ice

00:00:30.000 --> 00:00:34.000
formation and keep the electrical equipment at the right temperature.

00:00:34.000 --> 00:00:39.000
All four gap measurements are working, but one has dipped slightly below requirements.

00:00:39.000 --> 00:00:44.000
The condition will be monitored but is not currently expected to impact tonight's launch.

00:00:44.000 --> 00:00:49.000
Teams also are exploring the option of manually adjusting the ground systems valve in

00:00:49.000 --> 00:00:53.000
the mobile launcher platform to assist in increasing the pressure.

00:00:53.000 --> 00:00:58.000
We'll continue to provide updates on this potential issue as they become available.

00:00:58.000 --> 00:01:04.000
Liftoff is scheduled for 7:43 p.m. Eastern time from Launch Pad 39A.

00:01:04.000 --> 00:01:09.000
The launch window extends for about five minutes. This mission will deliver the S6 truss

00:01:09.000 --> 00:01:14.000
segment and the fourth of final large set of solar array wings.

00:01:14.000 --> 00:01:19.000
The arrays will provide 25 percent more power to the station and will fully power science

00:01:19.000 --> 00:01:23.000
experiments and support the station's crew expansion to six residents in May.

00:01:23.000 --> 00:01:29.000
There will be three spacewalks during this 13-day mission. Discovery also will take up

00:01:29.000 --> 00:01:34.000
the Japan Aerospace Exploration Agency's first resident crew member Koichi Wakata

00:01:34.000 --> 00:01:39.000
and bring back NASA astronaut Sandy Magnus, who's been living on station since the

00:01:39.000 --> 00:01:47.000
STS-126 mission in November of 2008. STS-119 is the 125th space shuttle flight and the

00:01:47.000 --> 00:01:52.000
28th flight to the station. It is the 36th flight for shuttle Discovery and the

00:01:52.000 --> 00:01:54.000
first flight in 2009.

00:01:54.000 --> 00:01:59.000
Discovery's crew of seven began their day this morning at 9 a.m. and have received

00:01:59.000 --> 00:02:04.000
medical checks by the flight surgeon. In about 45 minutes the crew will begin putting on

00:02:04.000 --> 00:02:10.000
their launch-and-entry suits before heading to the launch pad. At about 10:18 a.m. we

00:02:10.000 --> 00:02:14.000
began operations to load the external tank with more than 500,000 gallons of liquid

00:02:14.000 --> 00:02:18.000
propellants that will be used by the shuttle's three main engines to lift Discovery into

00:02:18.000 --> 00:02:24.000
orbit. Managers and engineers are in Firing Room 4 in the Launch Control Center at

00:02:24.000 --> 00:02:29.000
Kennedy Space Center in Florida monitoring the countdown. Tanking operations

00:02:29.000 --> 00:02:33.000
generally last about three hours and were completed earlier this afternoon.

00:02:33.000 --> 00:02:35.000