Final launch of space shuttle Endeavor set for today

When Space Shuttle Endeavour blasts into space for the final time today, the launch will be particularly emotional for the commander on board.

Back on the ground, Cmdr. Mark Kelly's wife, U.S. Rep. Gabrielle Giffords, will watch the shuttle's ascent. Three months ago, Giffords was clinging to life after a gunshot wound tore through her brain in January's Tuscon, Arizona, mass shooting.

Kelly will lead a crew that includes pilot Gregory H. Johnson; mission specialists Michael Fincke, Greg Chamitoff and Andrew Feustel; and European Space Agency astronaut Roberto Vittori. Liftoff is scheduled for 3:47 p.m. ET.

Endeavour has logged more than 103 million miles in space, blasting off 24 times, but its 25th flight will be its last.

As NASA's shuttle program winds down with the last launch scheduled this summer, many in the astronaut corps are wrestling with what to do next. For the foreseeable future, Russian rockets will be the only way for U.S. astronauts to get to space.

As for this mission, four spacewalks are planned. The space walkers will retrieve experiments, install new ones, refill tanks and lubricate parts at the International Space Station.

In its cargo bay, Endeavour will carry the Alpha Magnetic Spectrometer. At $1.5 billion, it is the most expensive piece of equipment a space shuttle has ever carried.

The AMS is designed to capture space particles like antimatter and dark matter which scientists know very little about but believe exist in the universe. The AMS will be mounted outside the International Space Station. If it's successful, it could lead to a better understanding of how our universe began and evolved.

(Via CNN)

UPDATE: NASA calls off today's shuttle launch, citing problems with one of the heaters' switch boxes.