Today at 1pm, we're joined for a live web chat with Dr Jeff Hoffman, a veteran of five space shuttle flights, including the first mission to retrieve and repair the Hubble Space Telescope in 1993. Please post your questions for him below.
Dr Hoffman has logged more than 1,211 hours in space and became the first astronaut to notch up 1,000 hours aboard the shuttle. He has travelled 21.5 million miles in space.
He flew twice on Columbia, which was destroyed on return to Earth in 2003, and once on Atlantis, which – weather permitting – is due to launch from Kennedy Space Centre tomorrow, marking the last mission of the shuttle era.
Hoffman has made numerous space walks and worked on tethered satellites that were dragged behind the space shuttle to generate electricity.
He holds a PhD in astrophysics from Harvard University and is now a professor at the Department of Aeronautics and Astronautics at MIT.
