Update at 12:26 p.m. ET. Launch Scrubbed:
NPR's Mark Stencel, who is at Cape Canaveral, reports NASA has scrubbed Endeavour's launch for at least 48 hours. On its twitter account NASA said it was working to fix two heaters associated with the shuttle's Auxiliary Power Unit 1.
The crew, Mark reports, was in the Astrovan headed to the shuttle and when news came in, it turned back around to take them back to the crew quarters. NASA said it would begin draining the external fuel tank. "Engineers will assess the issue," NASA announced on Twitter, and will give an update on the situation in press conference later today.
Our original post:
At 3:47 p.m. ET., the shuttle Endeavour is set to launch on its 25th and final flight. The launch is also the penultimate space shuttle mission. The 30-year-old shuttle program is set to end when Atlantis launches in June.
NASA released this stunning photo of the Endeavour on its final night in waiting amid a thunderstorm:
We'll update this post as launch time nears. Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.