Washington - The space shuttle Discovery docked Tuesday with the International Space Station on a construction mission that will eventually allow the station to double its crew.

The Discovery is delivering the fourth and final solar panel that will enable the ISS crew to grow from three to six astronauts.

Three spacewalks are planned to install the solar panels and conduct other construction projects. Two spacewalkers are scheduled to put the panels in place on Thursday with help from the station's robotic arm.

"Welcome to the space station, Discovery. We're glad you're here," the ISS crew said as the two orbiting spacecrafts made contact at 2120 GMT above Australia.

The mission delivered Japanese astronaut Koichi Wakata, who officially joined the permanent crew on the orbiting space station later Tuesday. He replaces US astronaut Sandra Magnus, who now joins the Discovery crew for the flight back to Earth.

About two hours after docking, the crews opened the hatches between the vehicles in a welcoming ceremony.

"We've been waiting for you for a while and understand you have some important things for us, first and foremost Koichi-san," said ISS commander Mike Fincke, referring to the weeks of delays Discovery faced due to safety concerns arising from hydrogen fuel valves.

In recognition of the first permanent ISS resident from Japan, Discovery astronauts awoke on Tuesday morning to Radio Exercise, a song used by Japanese schoolchildren to exercise and performed by the Tokyo Broadcast Children's Choir.

Kuniaki Shinakuri of Japan's Jaxa space agency called Wakata's arrival "a great accomplishment for Japan's ISS programme" and said that Wakata's stay will pave the way for future Japanese space efforts.

The shuttle launched Sunday after weeks of delays to inspect and study the hydrogen fuel valves and a later leak in a fuel vent.