"Six months, as you know, is a long time to be on orbit and away from family and friends," Williams said in an interview. "It's very good to be back on Earth."
As an ISS flight engineer, Williams worked, lived, ate and slept high in Earth orbit before returning to constant pull of gravity on Sept. 28 with his Expedition 13 commander Pavel Vinogradov and U.S. space tourist Anousheh Ansari.
Expedition 13, which launched on March 29, saw NASA's second return-to-flight shuttle mission and first new space station construction work since late 2002.
"It was an honor to be onboard the space station during that time," Williams said. "Obviously, there were a lot of key milestones met."
Among those, Williams said, was the success of NASA's second post-Columbia accident mission, STS-121 in July, which delivered European Space Agency astronaut Thomas Reiter to the ISS, bumping the station's population back up to a three-person crew.
Less than two months later, NASA's STS-115 crew aboard the Atlantis shuttle arrived to add a pair of new portside trusses and solar arrays to the orbital laboratory.
"It's a startlingly different configuration now with the additional solar arrays," Williams said as he recalled his last look at the ISS from his departing Soyuz spacecraft. "I jokingly said it borders on ugly right now, so we have to complete the assembly to get the other side to look the same."
Construction of the space station stalled after the 2003 Columbia accident as NASA worked to recover from the loss of the shuttle and its astronaut crew.
But after two test flights and one successful ISS assembly mission, the $100 billion project is once more underway as NASA prepares for the December launch of its Discovery shuttle's STS-116 mission.
"Every step is important," Williams said when Discovery rolled out to NASA's Florida launch pad Thursday. "We want to get all the laboratory modules up three and we want to increase [the station] to a crew of six. We need the shuttle to do that."
A brief emergency aboard the ISS in September, prompted by an overheating oxygen generator and chemical leak, proved the value of station crew training to Williams when he and his Expedition 13 crewmates responded.
"I think due to the training and the procedures, we went through the response not without thinking about it, but in a very methodical and logical way that saved the situation fairly early," he said.
Snapshots and silence
A colonel in the U.S. Army, Williams served as NASA's ISS science officer during the Expedition 13 mission and performed a host of experiments.
One such project, dubbed SPHERES, tested the ability of two free-flying satellites to determine their position in space.
But orbital photography, it seems, was Williams' forte. The astronaut set an all-time record for the most photographs taken during an ISS expedition. During Expedition 13, Williams snapshots of Earth, space and the ISS pushed the station's total photograph output past the 240,000 mark.
"I didn't set out to try to capture any records," Williams told SPACE.com, adding that orbital photography was one part hobby and one part travelogue to remember his mission. "I learned from my first flight that really, when you come back, the most important thing that you have are the pictures and video."
One photo session in particular stands out, in which Williams caught the brief eruption of the Aleutian Islands' Cleveland volcano.
"There are so many high points in six months," the astronaut said, adding that Cleveland's eruption was one of those unique moments. "It was a very short eruption, probably a bit longer than an hour, and was very exciting."
With Expedition 13 complete, Williams has racked up 193 days of orbital living and spent more than 19 hours working outside inside a spacesuit during three career spacewalks.
About 10 of his orbital days were spent during NASA's STS-101 shuttle flight aboard Atlantis.
But returning home was a no-brainer, the veteran spaceflyer said. For one thing, it's quiet.
"On the space station, as you know, you have continuous fans and pumps running, and some of these are louder than others," said Williams, adding that even the din of recovery crews on landing day on the steppes of Kazakhstan amounted to a whisper in his ears after Expedition 13. "For six months, not being able to get away from that noise, I really missed that."
Williams missed his family, wife Anne-Marie and two sons, more however, and is eagerly settling back into life moored to his home planet.
"Right now, we want to get our life back in order," Williams said. "I'll be working on things in the house that need to be worked on."
After that, he added, he'll think about what will follow his orbital trek.
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