Weather-wary NASA clears space shuttle for launch

CAPE CANAVERAL, Fla, Aug 26 (Reuters) With a wary eye on the weather, NASA managers have cleared the US space shuttle Atlantis for launch from Florida tomorrow to restart construction of the International Space Station.

The shuttle and six astronauts are scheduled to lift off at 4:30 p.m. (0200 hrs Ist) on the first station assembly mission since before the 2003 Columbia accident.

''We feel very good about where we are going into the weekend,'' said LeRoy Cain, the senior shuttle program manager at Florida's Kennedy Space Center.

The US space agency needs to fly 16 missions to the orbital outpost to finish construction of the half-built, 0 billion space station before the shuttle fleet is retired in 2010.

''This is the first of many steps we must take to complete the space station,'' program manager Mike Suffredini said.

Getting Atlantis off the ground will be the first challenge.

Thunderstorms and rain are expected to clear the area by the shuttle's launch time, which is determined by the rotation of Earth relative to the space station's orbit, as well as other factors such as daylight launch requirements.

That rule was imposed after the Columbia disaster, which was triggered by a piece of falling foam insulation that fell off the fuel tank and struck and damaged the shuttle. The ship broke apart 16 days later over Texas as it flew through the atmosphere to land, killing the seven astronauts aboard.

Any rain during liftoff might damage the spaceship's heat-shielding tiles, and a lightning strike could knock out the computers that control the ship. Even some kinds of thick, high clouds make launch hazardous.

Atlantis' mission follows two test flights, one in July 2005 and another last month, to demonstrate that safety upgrades made after the accident were successful.

Another disaster or serious problem likely would end the shuttle program and jeopardize the space station's future.

Engineers were assessing a lighting strike at the shuttle's seaside launch pad yesterday. The bolt is believed to have struck a cable that is part of the pad's lightning protection system, with no impact to the vehicle, launch director Mike Leinbach said.

NASA managers also were keeping tabs on a newly developed tropical storm that could threaten the Gulf Coast late next week.

The fifth named storm of the season, Ernesto, is expected to develop into a Category 1 hurricane by Monday, with 65-knot, or 119-km-per-hour, winds.

If NASA's Mission Control Center in Houston had to be evacuated, the shuttle likely would be forced to land early.

Suffredini said the launch team would do everything possible to install the 15,876-kg power module Atlantis is hauling to the station before coming home.

''We would undock from the space station and de-orbit the (shuttle) at the first safe opportunity,'' Cain said.

If necessary the shuttle could land with the module still in the cargo bay, but Cain said that would be last-choice option.

''I don't know that we've ever landed with that much cargo in the payload bay before,'' he said.

REUTERS VJ BST0630