After a nearly two-day pursuit, the US space shuttle Discovery arrived at the International Space Station (ISS) and docked with it at 5:19 p.m. EDT (2119 GMT)on Tuesday as they flew over southern Australia, according to NASATV.

The linkup took place some six minutes behind the planned docking time of 2113 GMT.

The US space shuttle Discovery docks wiht the International Space Station (ISS) at 5:19 p.m. EDT (2119 GMT)on Tuesday. [Xinhua]

Before arriving, Discovery's commander guided the shuttle through a 360-degree backflip so the station astronauts could photograph its belly. The digital pictures were immediately transmitted to the Earth. Experts will scrutinize the images for any signs of launch damage.

The station and shuttle crews will open the hatches between their vehicles and greet each other in about two hours. The first priority for the 10 astronauts, once united, was a crew member swap. Koichi Wakata, who arrived aboard Discovery, will switch seatliners with station astronaut Sandra Magnus and replace her as Expedition 18 Flight Engineer. Wakata will also be the first Japan Aerospace Exploration Agency's resident station crew member.

Discovery's mission will feature three spacewalks to help install the S6 truss segment to the starboard, or right side of the station and the deployment of its fourth and final set of solar array wings. Altogether, the station's arrays can generate as much as 120 kilowatts of usable electricity -- enough to provide about 42 2,800-square-foot (260 square meters) homes with power. The arrays will provide the electricity to fully power science experiments and support the station's expanded crew of six in May.

The truss is a high-tech girder structure made up of 11 segments. It provides the backbone for the station, supporting the US solar arrays, radiators and other equipment. After S6 installation, the truss will be 335 feet (102 meters) long.

The flight will also replace a failed unit for a system that converts urine to potable water.

The ISS' Urine Processing Assembly that removes impurities from urine in an early stage of the recycling process is not working. The entire Water Recovery System was delivered and installed during the space shuttle Endeavor's STS-126 mission in November, 2008. Astronauts were able to coax it into use by performing in-flight maintenance, but a distillation unit failed after Endeavor's departure.

Discovery, with seven astronauts aboard, was launched into space Sunday night. If all goes well, it is scheduled to undock from there on March 25, towards a planned March 27 landing at the Kennedy Space Center in Florida.

(Xinhua News Agency March 18, 2009)