Space shuttle Endeavour has blasted off on the next-to-last flight fo the programme under the command of Mark Kelly, the husband of shooting victim Gabrielle Giffords.
The congresswoman watched the launch in private from Kennedy Space Centre.
As many as 45,000 guests jammed NASA’s launch site. The crowd outside the gates was estimated to be in the tens of thousands.
It was the second launch attempt. Late last month, an electrical problem halted the countdown.
Endeavour and its six astronauts will arrive at the International Space Station on Wednesday. They are delivering a two billion dollar particle physics experiment. The mission will last 16 days.
Only one other shuttle trip remains.