Atlantis is locked down for storm

An eventful Tuesday saw Nasa order the shuttle back to its hangar to protect it from an approaching storm and then reverse the decision just hours later.

Assessments of updated forecasts had convinced managers that the weather would not damage Atlantis on the pad.

A rotating service platform should give adequate protection, they said.

Atlantis is set for a construction mission to the International Space Station (ISS).

It will deliver and fit the P3/P4 truss, a 17-tonne segment of the station's "backbone" that includes a huge set of solar arrays and a giant rotary joint to allow them to track the Sun.

The solar arrays, which will span more than 70m (240ft) when fully extended, will power science laboratories, living chambers and other systems onboard the ISS.

Depending on the effects of Tropical Storm Ernesto on Florida's Kennedy Space Center, a new launch date for Atlantis could be set once storm damage is evaluated and work resumes at the launch pad.

A launch attempt may be possible next week - just before the current launch window closes on 13 September.

If Nasa fails to fly Atlantis in that time, the next opportunity to lift off during daylight is in late October.

Only daytime launches have been permitted since the loss of the shuttle Columbia and seven astronauts in 2003.

Daylight enables the space agency to take pictures of the shuttle to check for debris from the external fuel tank that could damage the orbiter.

Nasa's administrator Mike Griffin has said the agency may lift the restrictions and allow launches at night if the Atlantis flight goes well.

The shuttle was almost halfway into the 12-hour journey back to its assembly building when Nasa managers reversed course.

"We made a call that surprised some folks," said launch director Mike Leinbach. "We feel good about the decision. This is the best way to go," he was quoted as saying by the Associated Press.

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