Space Shuttle Discovery STS-124 is scheduled to launch today at 5:02 PM EDT. They are on loading fuel as I type. Here's the latest update from NASA:

The loading of space shuttle Discovery's external tank with 500,000 gallons of liquid oxygen and hydrogen began at 7:38 a.m. EDT, and the "topping off" of the tank's propellants will continue until launch time. All systems onboard Discovery are functioning normally.

The weather is looking promising for launch day, according to Shuttle Weather Officer Kathy Winters. Isolated coastal showers may be in the area during the morning hours, but a sea breeze will develop in the afternoon, clearing the coast and causing any showers to move inland. There is an 80 percent chance of favorable weather at launch time.

This mission will carry the largest payload so far to the station and includes three spacewalks. It is the second of three missions that will launch components to complete the Japan Aerospace Exploration Agency's Kibo ["Hope"] laboratory. The crew will install Kibo's large Japanese Pressurized Module and Kibo's robotic arm system. Discovery also will deliver new station crew member Greg Chamitoff and bring back Flight Engineer Garrett Reisman, who will end a three-month stay aboard the outpost.

Perhaps the most important task, however, is a plumbing job to fix the toilet on the International Space Station. (Someone will presumably check their union cards before boarding.)

In other space related news, the Phoenix Mars Lander made a successful and spectacular landing Sunday and is sending back some amazing images of the Arctic Plain of Mars.

Blog coverage from earlier in the week:

Steve at WhitesCreek: Way to go, Scientists and Engineers, and their teachers back in 5th grade who showed them how to make a battery out of a potato...

Russ McBee: I'm frankly astounded at the technical skill necessary to make a landing mission like this work at all, but I'm left speechless and awestruck by the fact that NASA's engineers could direct a satellite, orbiting a planet millions of miles away, to capture a fleeting image of a second craft traveling thousands of miles an hour through its field of vision.

(All photos courtesy of NASA)

UPDATE: Mission underway after a perfect launch at 5:02, right on time. Nine minutes later Shuttle Discovery is in orbit, chasing down the International Space Station for rendezvous on Monday.