We chat to Dr Kathy Thornton, nuclear physicist turned NASA astronaut who went on to fly on four Space Shuttle missions. Dr Thornton flew for over 40 days and completed over 21 hours of EVA, including the famous operation to fix the blurry Hubble Space Telescope. We talk about her life as an astronaut, the Hubble fix and that fateful day in mission-control on Columbia's last re-entry.