On Friday, April 29, a mass audience that includes President Barack Obama will be watching a momentous event; thousands will watch in person and millions on TV.

No, it's not the Royal Wedding. While Prince William's wedding to Kate Middleton will certainly be watched by many, a sizeable crowd will focus on Cape Canaveral, Fla., to watch the final launch of the space shuttle Endeavour. NASA officials said they were not aware of the wedding when they moved the launch from April 19. The original launch was delayed because of a coinciding Russian Soyuz launch.

I didn't realize when the wedding was until we moved the launch date, NASA's associate administrator for space operations, Bill Gerstenmaier said. We set that date independently, and then as I was setting the date somebody called me and told me about the wedding.

The launch date is not going to be moved again, regardless of the big wedding in the U.K. That's because the space shuttle can't visit the space station when its orbit is at a certain orientation -- called the beta angle -- relative to the sun. The angle changes constantly, but when it is more than 60 degrees, the sun keeps shining on the spacecraft because (as seen from orbit) the Earth never passes between the shuttle and the sun. When it isn't docked, the shuttle can do slow rolls to make sure one side doesn't heat up too much. But when it is docked, that can't happen.

We work beta constraints and we work launch-range constraints. I haven't yet put on our manifest charts 'wedding constraints. So we didn't factor that into our thinking, Gerstenmaier said.

In an interview with SPACE.com, NASA's space shuttle director, Gary Horlacher, said he realizes the royal wedding will get a lot of media coverage; but he hopes people are still interested in Endeavour's final launch.

The last launch of the Endeavour space shuttle should get some media attention of its own. Not only is it the end of a historic ride for the well-traveled fleet, but it also will feature commander Mark Kelly, husband of congresswoman Gabrielle Giffords, who was nearly shot to death earlier this year. Both Giffords and the President will be in attendance as Endeavour makes its final journey into space.

The 14-day mission will see the crew of the Endeavour deliver the Alpha Magnetic Spectrometer (AMS) and spare parts including two S-band communications antennas, a high-pressure gas tank, additional spare parts for Dextre to the International Space Station. After it finishes up, NASA will conclude the space shuttle program with the Atlantis. Following that, the three remaining space shuttles and a fourth prototype will head to museums across the country.

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