As they prepare for what could be a record-tying launch attempt, Endeavour astronauts are mostly relaxing today following launch scrubs on consecutive days because of weather.
"Taking it easy today," mission commander Mark Polansky wrote in a Twitter post this morning. "Two scrubs in a row take a little out of you physically."
The mission's sixth launch attempt is scheduled for 6:03 p.m. Wednesday.
Another scrub Wednesday would tie the record for the most by a shuttle mission, set by Columbia missoins in 1986 and 1995.
The STS-61C mission in 1986 - piloted by President Obama's nominee for NASA administrator, Charlie Bolden, and also including current Florida Sen. Bill Nelson as a payload specialist - scrubbed six times and launched on a seventh attempt.
STS-73 in 1995 also launched on its seventh countdown.
NASA technically only counts a delay as a "scrub" if a shuttle has been fueled for launch, so Endeavour's delay Saturday because of lightning strikes near the launch pad wouldn't be counted.
But whatever you call it, the mission has endured five launch delays with countdowns in progress, and a sixth Wednesday would tie the other missions.
Polansky wrote yesterday that his crew was undeterred by the delays.
"We're fine in spite of this, and we'll hope for Wed.," he wrote on Twitter, noting that "it's just not easy to launch a shuttle."
Today's forecast from the Air Force's 45th Weather Squadron suggests NASA would have struggled again to launch Endeavour today, and the chances are better Wednesday.
There's a 60 percent chance of favorable launch weather Wednesday, compared to 40 percent today. But the odds dip back to 40 percent again on Thursday, should NASA elect to make a launch attempt then.
That would require cutting some content from the planned 16-day International Space Station assembly mission, most likely the last of five spacewalks.
Today's poor forecast was the main reason for not trying to launch again today, though NASA also prefers not to make astronauts and launch crews go through three countdowns in a row.
As Polansky said, it's tiring work.
The day off also gives KSC workers a chance to fix a loose cover over a thruster before anticipated rain showers reach the pad.
Overnight, they closed the rotating service tower around Endeavour at launch pad 39A to be able to access the forward thruster.
Work to replace the cover started at 8:30 a.m. and was expected to take about five hours, according to a United Space Alliance spokeswoman. That includes the replacement, tests and inspections.
The service tower is scheduled to be retracted at 11 p.m. to prepare to fill up Endeavour's external fuel tank again Wednesday around 8:30 a.m.
Mission managers plan to meet at 8 a.m. to decide whether to proceed with fueling.
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