Photo credit: Pat Benic/UPI/Newscom

I can’t believe something as important to me as the penultimate shuttle launch slipped my mind, but somehow it did: I forgot that Endeavour‘s rescheduled launch date was today, so I was caught off-guard this morning by the news that she had blasted off on her final mission, designated STS-134, at 8:56 a.m. EDT, or just before I got up at 7 a.m. mountain time. The official launch video, for those who enjoy such things, is here. (For some reason, NASA has disabled embedding on the video; I have no idea why, considering Discovery‘s final launch clip was — and still is — readily available.) The vid is somewhat disappointing — it’s almost all overexposed footage from the fish-eye cam on the top of the external fuel tank, with the earth appearing as a big white crescent in the background and the tank itself nearly lost in the glare — but there is some interesting stuff at about 6:00, when the shuttle rolls to reorient itself to Earth, and at 8:45, when the tank is jettisoned and the orbiter lifts free. Watch closely during that sequence; you can actually see puffs of gas from the shuttle’s maneuvering thrusters.

This is the 25th flight for Endeavour, which is the youngest of the shuttle fleet, and also, I believe, the lightest in weight. (Interesting tangent: I read an interview not too long ago with one of the engineers who designed the shuttles — sorry, I’ve lost the link and the guy’s name — and he said they were intended to go 100 flights each and in his opinion, they are still capable of doing so. Just a little food for thought…) Named after Captain Cook’s sailing ship HMS Endeavour, she was constructed as a replacement for the destroyed Challenger, flying for the first time in 1992, and was the first shuttle to make a service call to the Hubble Space Telescope. She also carried the first American-built segment of the International Space Station.

On this flight, Endeavour is carrying spare parts for the ISS, as well as a scientific package called the Alpha Magnetic Spectrometer (AMS). For something with such a dry name, the AMS actually sounds pretty exciting, or at least potentially so; it’s a collection of eight different instruments designed to look for clues to the origins of the universe, including the mysterious substances known as dark matter and anti-matter. If those long-theorized things actually exist, the AMS is supposed to be able to find them. Endeavour‘s crew will make four spacewalks to install all this stuff. The mission is scheduled to last 16 days, with a middle-of-the-night landing in the wee hours of June 1.

One final word about the photo at the top: Endeavour launched under an overcast sky this morning, leading to some very cool videos of her disappearing into the clouds and at least one really awesome photo of her punching through the cloud deck above. Man, I love this stuff…