WASHINGTON, Sept. 17 (Xinhua) -- The U.S. space shuttle Atlantis undocked from the International Space Station (ISS) at 8:50 a.m. EDT (1250 GMT)Sunday after astronauts had finished the installation of new solar panels to the orbiting outpost, NASA TV reported.

After a busy week of challenging construction work, the Atlantis crew bid farewell to its host -- the station crew -- and left the space station.

The hatches between the station and shuttle Atlantis closed at 6:27 a.m. EDT (1027 GMT).

The two crews conducted leak checks before Atlantis undocked slowly from ISS and began its nearly three-day-journey home.

Following the undocking, Pilot Chris Ferguson will do a 360-degree fly-around of the station to allow his crewmates to collect imagery of the newly-expanded station.

The fly-around, which will reveal the station's new configuration in full view, will last for more than an hour.

Atlantis' STS-115 mission is the first of a series of the shuttle missions that will perform on-orbit construction of the station.

Atlantis delivered the new integrated truss to the station, and its crew used the shuttle and station robotic arms to attach the truss to the orbital outpost and then conducted three arduous spacewalks in four days to prepare the truss and its solar arrays for operation.

The truss' 240-foot (73 meters) solar arrays will eventually double the station's power capabilities, setting the stage for future expansion.

The STS-115 and Expedition 13 crew held the traditional joint crew news conference earlier Saturday. STS-115 Commander Brent Jett said this mission is a good start for the series of upcoming construction flights.

"All of the rest of the assembly missions are going to be challenging," Jett said. "We have similar payloads flying in the future."

"We are off to a good start on assembly. I think we can pass along a lot of the lessons to the future crews," he added.

Atlantis is scheduled to touch down at 5:57 a.m. EDT (0957 GMT)Wednesday at Kennedy Space Center in Florida. Enditem