Thursday, June 29 2006 12:09 Hrs (IST) - World Time -

Washington: The official countdown for the launch of the space shuttle Discovery began as the seven-member crew made final preparations for Saturday's launch. The launch countdown officially began at 5 p.m. (2100 GMT) Wednesday at the Launch Control Center at Kennedy Space Center in Cape Canaveral, Florida, NASA announced at its website. The targeted launch time is 3.49 p.m. (1949 GMT) on Saturday.

The countdown started at 43 hours. It includes 28 hours of built-in hold time, the National Aeronautics and Space Administration said. During a countdown status briefing Wednesday, NASA Test Director Jeff Spaulding said Discovery was in excellent shape. "We're tracking no issues in our preparation at this point," Spaulding said. But there is a 60 percent chance that weather may prevent launch.

The launch could be delayed 24 hours, but NASA said the forecast is the same the next day. The Discovery, grounded since last July's flight because of continuing problems with shedding foam on takeoff, will carry German astronaut Thomas Reiter on its voyage to the International Space Station (ISS). Reiter will join two other astronauts who travelled in April to the ISS in a Russian Soyuz craft - the vehicle that has taken up much of the slack during the US shuttle groundings. Last summer's accident-ridden US flight was the only shuttle launch since the fiery death of seven astronauts on board Columbia as it re-entered Earth's atmosphere in 2003. The final three days of preparations include filling up the 47-metre high external fuel tanks with about 2 million litres of liquid oxygen and hydrogen.

The crewmembers, including two women, will be awakened at 0915 GMT Saturday (5.15 a.m.), followed by breakfast and the obligatory group photo. About four hours before launch, the crew will climb into their space suits.

Discovery, NASA's workhorse with a record 31 flights since its maiden flight in 1984, will be carrying about 14 tonnes of cargo including equipment such as the so-called Minus-eighty Laboratory Freezer, needed to hold samples in deep-freeze temperatures.

The 12-day mission will also deliver water, food and clothing to the station. Astronauts are to carry out urgent repairs on the ISS and test new technology for in-space repairs of the shuttle. The return is slated for July 13 at 1445 GMT to Kennedy Space Center.

Reiter will remain on board with ISS commander Pavel Vinogradov, a Russian cosmonaut, and US flight engineer Jeffrey Williams.

Saturday will mark the 115th launch of a US shuttle, and the 18th launch of a US shuttle to the space station.

Two flight security specialists spoke out against Saturday's launch, but top leadership decided to carry on. NASA grounded Discovery and its other shuttle, Atlantis, for another year after large pieces of solid-foam-coating on the external fuel tanks peeled off and hit the delicate ceramic heat shield tiles on the outside of the spacecraft.

A similar incident was blamed for damaging the heat shield on takeoff of Columbia in 2003, opening a wedge through which superheated air entered the shuttle on its re-entry over Texas. All seven astronauts on board were killed.