Space shuttle Endeavour sits atop launch pad 39A before Mission STS-134 at the Kennedy Space Center in Cape Canaveral
Space shuttle Endeavour sits atop launch pad 39A before Mission STS-134 at the Kennedy Space Center in Cape Canaveral. It will be the last mission for the spacecraft. Reuters

From NASA's web site:

Shuttle Launch Director Mike Leinbach has scrubbed today's STS-134 launch attempt because of an issue associated with Auxiliary Power Unit 1 heaters. There will be at least a 48-hour scrub turnaround while engineers assess the issue. NASA Television will air a news conference later this afternoon.

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