CAPE CANAVERAL, Fla. - The space shuttle Discovery is just one day away from launching into orbit before sunrise on Monday on what is expected to be NASA's last scheduled shuttle flight to lift off in darkness.
Discovery and a crew of seven astronauts are slated to make an Easter Monday shuttle launch toward International Space Station. The shuttle is launching hot on the heels of a Russian Soyuz spacecraft that ferried three new crewmembers — two Russians and one American — to the orbiting laboratory this morning.
"The crew is ready to go and we're looking forward to our mission to the International Space Station," shuttle commander Alan Poindexter told reporters after arriving at the launch site earlier this week.
The space station's population doubled in size when the Soyuz arrived early Sunday, jumping to a full crew of six for the first time since November 2009. When Discovery's own four-man, three-woman crew arrives there will be an even larger crowd — 13 people on the station.
"Have 'em scoot over a bit, 'cause here WE come!" Discovery astronaut Clayton Anderson wrote on his Twitter page, where he is chronicling the shuttle flight as Astro_Clay.
Night shuttle launch
Discovery is slated to lift off at 6:21 a.m. EDT (1021 GMT), about 47 minutes before sunrise, which makes it NASA's last scheduled shuttle mission to launch in darkness. There is an 80 percent chance of good weather for the launch attempt, with fog the only concern.
Early-rising skywatchers along the United States East Coast may have a chance to see the shuttle on its way into orbit, weather permitting [how to watch the shuttle launch].
The International Space Station is also expected to fly over Discovery's launch site about 15 minutes before liftoff. The space station weighs nearly 800,000 pounds and is as long as a football field. It can be easily seen from Earth by the unaided eye if you know where to look.
Discovery's upcoming mission is one of four final shuttle flights planned before NASA retires its space plane fleet in the fall — ending nearly 30 years of shuttle spaceflight. It is the second-to-last mission for Discovery, the oldest of NASA's three shuttles.
Shuttle weather officer Kathy Winters said Discovery's launch has the potential to be stunning, with the shuttle launching in darkness just before sunrise, then brightening noticeably as it reflects sunlight on the still-dark ground during the climb into space. Once the sun begins to rise, it may illuminate the shuttle's exhaust plume in a rainbow of colors, she added.
"It should be a really, I think, a beautiful sight," Winters said. "I'm hoping that the visibility holds out for us."
NASA has two chances to launch Discovery before mission managers would stand down for three days to avoid another space traffic jam with a secretive unmanned Air Force space plane that is slated to launch April 19 (close to the shuttle's landing day).
Stocking up station
Set to launch spaceward aboard Discovery with Poindexter are rookie pilot Jim Dutton and mission specialists Dottie Metcalf-Lindenburger, Rick Mastracchio, Stephanie Wilson, Clayton Anderson and Japanese astronaut Naoko Yamazaki, who represents the Japan Aerospace Exploration Agency.
Metcalf-Lindenburger is a former high school teacher, while Yamazaki is Japan's second-ever female astronaut to launch into space.
Together the seven-astronaut crew will deliver a nearly 27,000-pound (12,246-kg) cargo module packed with science experiments, supplies and other gear — including a new astronaut bedroom and a novel system designed to create water from waste hydrogen and carbon dioxide gas.
The shuttle is also hauling a new gyroscope and ammonia cooling system tank for the space station — pieces so large that only NASA's space shuttles can carry them. It will take three spacewalks to install them on the space station.
It's a busy mission for the astronauts and for NASA.
The space agency will celebrate the 29th anniversary of its shuttle program on April 12, just before President Barack Obama is expected to visit Florida on April 15 for a space summit to discuss details of his plans for NASA's future.
At the same time, NASA's astronaut corps and shuttle engineering teams are taking great care to make each of the last shuttle missions safer than the last.
"This is a very human space program, not just with the humans flying in the shuttle but with the folks building it, preparing it and getting ready to launch it," said shuttle integration manager Mike Moses. "I don't think there's too many people out there right now at their desks worried that we're about to end. They're all looking forward to Monday morning and a launch."
SPACE.com is providing complete coverage of Discovery's STS-131 mission to the International Space Station with Managing Editor Tariq Malik in Cape Canaveral, Fla., and Staff Writer Clara Moskowitz based in New York. Click here for shuttle mission updates and a link to NASA TV.