Washington - Space shuttle Endeavour continued to enjoy a problem-free journey throught space Saturday on its way to link up with the International Space Station (ISS).

The shuttle is expected to rendezvous with the station around 0100 GMT on Sunday, 24 hours after takeoff from Cape Canaveral.

The shuttle's 15-day mission will include four spacewalks to repair joints that allow the station's solar panels to rotate toward the sun. Astronauts will also install a nitrogen tank, a global positioning system and a camera outside the ISS

Work will also focus on preparing the space station for expansion and delivering items to make it a more comfortable place to live. Those additions include an exercise machine, a second toilet, two sleep stations and a water recycling pump to turn urine into drinking water. The shuttle crew is also bringing two food warmers and a larger refrigerator.

The upgrades to the space station's living space should enable it to house more residents on longer-term assignments after the retirement in 2010 of the US fleet of aging reusable orbiters.

The payload will be delivered in the reusable, Italian-built Leonardo module that will be transferred to the ISS using the shuttle's robotic arm. Astronauts will later fill it with old equipment and scientific samples and bring it back to Earth aboard Endeavour.

Endeavour astronaut Sandra Magnus will stay behind as a member of the ISS crew while Greg Chamitoff will return to Earth with the seven- member crew after more than five months in space.

While en route Saturday, the crew will use a camera attached to a robotic arm to check for any damage to the shuttle sustained during takeoff. Since the launch occurred in the evening, it was difficult to tell whether any insulation had broken off from the shuttle. (dpa)