In this Feb. 4 file photo, astronaut Mark Kelly prepares to discuss his decision to command the final flight of the Space Shuttle Endeavor during a news conference at Johnson Space Center in Houston, as his wife, U.S. Rep. Gabrielle Giffords, recuperates from a gunshot wound to the head in a Houston hospital. NASA's mighty astronaut corps has become a shadow of what it once was. And it's only going to get smaller. It's down to 60 from an all-time high of 149 just a decade ago, with more departures coming once Atlantis returns this week from the very last space shuttle voyage. In fact, Kelly is retiring in another few months to write a memoir with his wife.
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