Weather Remains 70 Percent Go For Shuttle Launch Friday

NASA is counting down to the planned launch Friday of shuttle Atlantis and six astronauts and the weather forecast remains favorable for an on-time liftoff.

The shuttle and its crew are scheduled to blast off from launch pad 39A at Kennedy Space Center at 2:20 p.m., midway through a 10-minute opportunity. NASA selects the middle of the window because that is when the rotation of the Earth and Atlantis systems give the shuttle the most propulsive power on the way uphill.

The Air Force 45th Space Wing Weather Squadron issued a forecast today that says there is a 70 percent chance conditions will be good enough to go.

More specifically, the forecast says:

"High pressure continues to dominate Florida and is expected to persist through Sunday. As a result, favorable weather conditions will continue for pre-launch and launch operations. Early mornings will have light winds with a slight chance of a coastal rain shower. Winds will be out of the east and increase through the afternoon hours with peak winds near 18 to 22 knots. Partly cloudy and generally dry conditions will dominate the afternoon hours. On launch day, low clouds will form and move into the area due to afternoon heating and convergent low-level flow. This will bring a chance of a low-cloud ceiling in the afternoon.

Our primary concern for launch is a low-cloud ceiling. Weather remains similar for a 24-hour and 48-hour delay; however, winds on Sunday will increase enough to make crosswind conditions more of a concern for Return-to-Launch Site (RTLS) operations at the SLF."

At the space center today, engineers and technicians will:

++Configure avionics systems for launch.

++Review flight software stored in mass memory units and display systems.

++Verify backup flight system software in Atlantis’ general purpose computer.

Navigation systems were activated and tested earlier today and preparations were completed in advance of the loading of cryogenic reactants into the shuttle's fuel cell system. The system combined liquid hydrogen and liquid oxygen to generate electricity to power all spaceship systems.

Crew equipment is being stowed in the shuttle's crew compartment and preliminary flight deck inspections are under way.

NASA will hold its prelaunch news conference a little later this morning. The briefing is scheduled for No Earlier Than 11 a.m. and will be broadcast live in The Flame Trench. Click the NASA TV box on the right side of the page to launch our NASA TV viewer and live coverage.