What were you doing when the International Space Station (ISS) was first being assembled in the year 2000? Maybe you were at school. Perhaps you had just started a new job. But one astronaut, Jeffrey Williams, was there in space at the beginning – and he’s about to go back again.

On May 20, 2000, he was on board the Space Shuttle Atlantis STS-101 mission as it docked with the ISS in its infant form of just two modules (Zarya and Unity), performing important maintenance of the station and delivering supplies ahead of the arrival of the first long-term crew on November 2 that same year. Now, 16 years later, Williams, 58, who is also a grandfather, is about to launch to the space station again – but this time, the ISS is essentially fully complete and operational.

Today at 5.26 p.m. EDT (9.26 p.m. GMT), Williams will launch with Russian cosmonauts Alexey Ovchinin and Oleg Skripochka as part of Expedition 47. This will actually be Williams’ fourth flight, having flown to the station previously in 2006 and 2009. For Skripochka, it's his third flight, while Ovchinin is on his first.

The launch will be streamed live on NASA TV, which you can watch below. Docking is expected at 11.26 p.m. EDT (3.26 a.m. GMT on Saturday), with the hatch opening a little over an hour later.

 

 

 

"It occurred to me that I've had the opportunity to really cover the history of the building of the International Space Station," Williams said prior to launch, reported The Planetary Society. "Now, its assembly is complete; we finished it up about the time I was there last. My visit before that was halfway through. So now, it's in full utilization mode and I look forward to personally sort of completing the story of the International Space Station."

This is what the station looked like the first time Williams' visited in 2000...

^NASA

...and this is what it looks like now.

^NASA

On board the station, Williams and co will join the existing crew of NASA’s Tim Kopra, Roscosmos’ Yuri Malenchenko, and ESA’s Tim Peake. They are replacing the previous crew of Scott Kelly, Mikhail Kornienko, and Gennady Padalka, the former two of which became the first to spend a year in space. The rest are only staying for six months.

Kelly set a new record for the longest time spent in space by an American during that extended stay, 534 days across four missions. But Williams is set to eclipse that record on this mission, specifically on September 7. When he returns later in September, he will have spent about two weeks longer in space than Kelly.

During the mission, the crew will (as usual) be performing a huge range of experiments. One of these will be to try out a new small exercise machine called the Miniature Exercise Device (MED-2). For eventual missions to Mars, using less bulky exercise equipment than is currently used on the ISS will be essential.

^{The Soyuz rocket is seen here ahead of the launch from Kazakhstan. NASA/Aubrey Gemignani}