Michael McCulley speaks to a crowd gathered in front of the Space Mirror Memorial to honor space shuttle.

Michael McCulley, former astronaut and chairman of the Astronauts Memorial Foundation, speaks to a crowd gathered in front of the Space Mirror Memorial at the Kennedy Space Center Visitor Complex in Florida to honor space shuttle Challenger's STS-51L crew members who gave their lives for while furthering the cause of exploration and discovery. 2011 marks the 25th anniversary of the loss of Challenger, which broke apart over the Atlantic Ocean 73 seconds into flight on Jan. 28, 1986.

NASA/Jack Pfaller