Seven astronauts have snoozed away
the days before their planned launch aboard the space shuttle Endeavour, but it
is all part of their plan for an overnight mission so extreme that one
spaceflyer dubbed it a "stealth flight."
Endeavour is poised to blast off
from Florida Wednesday morning at 5:40 a.m. EDT (0940 GMT) on a grueling 16-day
construction flight to the International Space Station. To rest up for the
predawn liftoff, the shuttle's six-man, one-woman crew has been going to sleep
in the morning and waking up at night.
"This represents one of those
flights where we have to shift into a completely different time zone," said
Endeavour astronaut Julie Payette, who represents the Canadian Space Agency.
"For that, we've become a bit of a stealth flight."
Payette and her
crewmates are due to wake up tonight at about 6:45 p.m. EDT (2245
GMT) and eat breakfast about a half-hour later, when most people on the East
Coast may be sitting down to dinner. Their mission has been delayed since June
13, when a hydrogen gas leak in a vent line on Endeavour's external tank
prevented the first launch attempt.
NASA calls the process "sleep
shifting" and it is something astronauts do regularly to tailor their day-night
cycle, or circadian rhythm, to the rigors of a specific space mission or single
event, such as a docking or spacewalk at the International Space Station.
Sleepy science in space
By adjusting their daily routines,
the astronaut are able to stay alert and focused no matter when their mission
"days" begin, NASA officials said.
For example, during Endeavour's construction
flight the astronauts plan to perform five tricky spacewalks and
challenging robotic arm work using three space cranes to install a new Japanese
experiment porch. The first spacewalk will begin Saturday at 12:30 a.m. EDT
(0430 GMT) and last more than six hours.
"We require crews to sleep shift in
order to meet critical mission objectives that must occur during their usual
sleep periods," said NASA flight surgeon Terrance Taddeo, chief of the Medical
Operations Branch at the Johnson Space Center in Houston.
"If done properly the crews avoid the performance decrements associated with sleep
deprivation and circadian desynchrony."
In space, the shuttle and station
orbit Earth once every 90 minutes, which gives astronauts 16 sunrises and
sunsets a day, instead of just one. That means that rather than 12 hours of
light and 12 hours of night, they make the switch every 45 minutes. If left
unchecked, that can cause serious disruptions in crew work and rest cycles,
NASA officials said.
In addition to changing their sleep
schedule before launch, astronauts are also subjected to modified lighting
conditions inside their crew quarters that simulate their daily schedule
regardless of whether the sun is up outside. The swings between high-intensity
light and darkness typically begin between three and 10 days before a launch,
depending on the time shift, and mimic the sun's role in resetting a person's internal
clock each day, NASA officials said.
Astronaut mealtimes, flight
simulations, mission training and all other activities are shifted accordingly,
and even Mission Control teams adjust their schedules for an upcoming
spaceflight, a NASA spokesman told SPACE.com.
Red eye trip
Payette said she is hopeful that the
public will follow her crew's construction marathon ahead at the International
Space Station despite its nocturnal schedule. The mission is NASA's third
shuttle flight of the year and the first ever to boost the space station's
population to 13 people, its
highest ever.
The space station doubled its
permanent crew size to six people in late May. Two Russian cosmonauts and
astronauts from the United States, Japan, Belgium and Canada are now aboard the
station and represent all of the outpost's major international partner space
agencies.
"It's truly exciting to go and join
six other people on the space station that represent all five partner
agencies," Payette said, adding that it will be the first time two Canadians
are in space simultaneously. "We'll be 13 on board, that'll be quite
interesting. We'll definitely tell you how that was."
SPACE.com is providing continuous
coverage of Endeavour's STS-127 mission with Staff Writer Clara Moskowitz in Cape Canaveral, Fla., and
Senior Editor Tariq Malik in New York. Live launch coverage begins at 12:30
a.m. EDT (0430 GMT) Wed. Click
here for mission updates and SPACE.com's live NASA TV video feed.
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