After saying goodbye and closing the hatches, Discovery crew members smoothly sailed away from the ISS at 5:32 am (1030 GMT).

"Discovery has physical separation," shuttle Commander Pam Melroy reported to mission control in Houston, Texas, over on open radio channel.

"Thank you guys for the module and all your help," responded Peggy Whitson, the station commander.

Before heading home the shuttle will perform a fly-around to allow crew members to collect video and imagery of the station in its new configuration.

Discovery arrived at the station on October 25, delivering the Harmony module, which was installed during the first of the mission's four spacewalks.

The module will eventually connect together two Japanese and European scientific laboratories to be delivered to the ISS in the coming months.

During the third spacewalk, the crew also moved a truss and installed a pair of solar arrays.

But the mission underwent unforeseen modifications after astronauts discovered that one of the solar arrays on the truss was torn and needed fixing.

American Scott Parazynsky, a medical doctor by profession, spent more than four hours attached to the end of a robotic boom knitting together the damaged panels with makeshift wire "cufflinks" to fix the problems caused by a snagged wire when the panels unfurled.

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