The US space agency NASA says the space shuttle Endeavour is on track for a scheduled nighttime lift-off. VOA's Jessica Berman reports space officials say Endeavour's payload is one of the heaviest in the history of the space shuttle program.

The crew of space shuttle Endeavour have spent hours studying the plan for a busy 15 days in space

The space shuttle Endeavour is scheduled to blast off a little bit before 01:00 UT Saturday from the launch pad at the Kennedy Space Center in Florida.

NASA Test Director Charlie Blackwell-Thompson said final preparations are virtually complete inside and outside the shuttle for its 15-day mission to the International Space Station.

"All of our systems are in good shape. Countdown work is on schedule. I have no issues to report," Blackwell-Thompson said. "Endeavour is ready to go. And we are really excited to share our version of a sunrise tomorrow night."

Carrying almost 16,000 kilograms worth of supplies and equipment, NASA officials say Endeavour's payload is one of the heaviest ever ferried by a shuttle to the International Space Station.

It is weighted down with extra bedrooms, a bathroom and kitchenette to expand living space aboard the space station to double the number of long-duration astronauts aboard from three to six by the middle of next year.

Also in the payload, the first recycling system to come aboard the ISS that will purify waste water and urine into drinking water for the crewmembers.

Endeavour's crew will perform four complicated space walks to repair and lubricate a massive solar alpha rotary joint that has become stuck with metal shavings. The astronauts will also perform preventive maintenance on the second solar joint.

The alpha joints must work properly for the solar arrays to track the sun for maximum power.

Barring difficulties, Endeavour is scheduled to return to Kennedy Space Center Florida on Saturday November 29.