Launch of Dawn Postponed 4 Hours to Sunday, July 8

The launch of NASA’s Dawn spacecraft aboard a United Launch Alliance Delta II rocket has been postponed 24 hours.

A lightning advisory this morning precluded the start of the Delta II second stage fueling as scheduled. If weather remains unacceptable this afternoon, fueling will be performed on Friday. Also this morning, the temperature within the fairing was causing the required temperature of the second stage to be too warm for fueling to begin. The fairing temperature is being lowered by ten degrees so that loading of oxidizer can begin this afternoon if weather is acceptable.

The countdown dress rehearsal scheduled for today has also been postponed until Friday.

The launch window on Sunday, July 8, extends from 4:04 to 4:33 p.m. EDT. The chance of not meeting the launch weather criteria on Sunday is 60%. Required launch telemetry assets downrange will be in place to support the launch.

The Dawn mission science briefing scheduled for Friday, July 6 will be held as scheduled starting at 1 p.m. EDT. The prelaunch press conference will be held on Saturday at 1 p.m. following the Launch Readiness Review.