The main topic of the news item is______.

(1)The space shuttle Endeavour is taking off on its final endeavor. The launch was delayed due to mechanical problems, but NASA officials said those were all fixed.
    The shuttle and its crew are headed to the international space station. This is a 16-day mission and the next-to-the-last mission for the space shuttle program. Mae Jemison has flown on Endeavour before. On that mission, she became the first African-American woman to travel into space. She said yesterday’s launch brought up mixed emotions.
    "Things are transitioning. When we spoke last year, we were there talking about the fact that the shuttle era was coming to an end, and now the United States was putting more of its research money into how to do interplanetary travel, how to come up with the kinds of engines that are needed to go, to taking us to an asteroid.(2)So, that transition is great, but it’s sort of hard to see the shuttle program ending. "