NASA, the nation and the world are observing this week the anniversaries of human losses in spaceflight: Apollo 1 (forty six years ago Sunday, January 27), Challenger (twenty seven years ago yesterday, January 28), and Columbia (ten years ago this coming Friday, February 1).
Here is a link to a NASA multimedia presentation for today's Day of Remembrance.
NASA - Day of Remembrance
Alan Boyle has more on the impact of these tragedies on space exploration and links to media coverage of each event.
NASA celebrates its fallen astronauts