The National Aeronautics and Space Administration (NASA) estimates that without a servicing mission to replace key components, the Hubble Space Telescope will cease scientific operations in 2008. In January 2004, then-NASA Administrator Sean O'Keefe announced that the space shuttle would no longer be used to service Hubble. He indicated that this decision was based primarily on safety concerns in the wake of the space shuttle Columbia accident in 2003. Many critics, however, saw it as the result of the new Vision for Space Exploration, announced by President Bush in January 2004, which focuses NASA's priorities on human and robotic exploration of the solar system. Hubble supporters sought to reverse the decision and proceed with a shuttle servicing mission. Michael Griffin, who became NASA Administrator in April 2005, stated that he would reassess whether to use the shuttle to service Hubble after there were two successful post-Columbia shuttle flights. The second post-Columbia flight took place successfully in July 2006. In October 2006, NASA approved a shuttle mission to service Hubble. That mission is now scheduled for October 8, 2008.