Dr. Grunsfeld is Deputy Director of STScI and a retired NASA astronaut, nicknamed the "Hubble Repairman" because he was the lead mission specialist on the three shuttle flights to repair and refurbish the Hubble Space Telescope. On 19 Dec 2011, it was announced Dr. Grunsfeld will take over as the new administrator for NASA's Science Mission Directorate on 4 January 2012.