Two astronauts have moved outside the International Space Station to carry out maintenance work.
They will remove a new ammonia tank from the shuttle and disconnect the station's old tank that supplied the cooling system. It will take 3 spacewalks to complete the job.
"The US space shuttle Discovery successfully docked with the International Space Station early Wednesday," NASA said.
They were also supposed to do some battery work on the far left end of the space station, along the sprawling power truss. But NASA cancelled the task this week because of concerns that the 2 might get electric shock.
The work instead will be carried out on the next shuttle flight, once the astronauts' suits are better protected.