The International Space Station as it is today. This image was taken in July 2009 by departing astronauts on the space shuttle Endeavour after they undocked from the outpost during the STS-127 mission.
This story was updated at 5:07 p.m. EDT.
Space shuttle Discovery is closing in on the International Space Station for a late Sunday rendezvous in orbit around Earth.
Discovery and a crew of seven astronauts are due to dock at the space station tonight at 9:04 p.m. EDT (0104 Aug. 31 GMT) and boost the outpost?s population to a record-tying 13 people. The shuttle is packed with nearly 8 tons of supplies and new science gear.
?I?m looking forward to seeing the station,? Discovery commander Rick Sturckow, who is making his fourth trip to the orbital outpost, told SPACE.com before launching late Friday. ?Every time we?ve been there, it?s gotten a little bigger.?
The International Space Station is currently home to six astronauts and has a wingspan that could cover an American football field. Astronauts have compared its nine main rooms of living space as comparable in size to the cabin of a jumbo jet.
Sturckow will have a more challenging approach for tonight?s docking because of a small thruster failure in a system used for fine attitude control adjustments. Discovery will rely on its larger, primary reaction control thrusters, which have more of a kick and consume more fuel, mission managers said.
?I would characterize it as slightly more challenging,? said deputy shuttle program manager LeRoy Cain, adding that when the bigger thrusters fire, astronauts can?t miss it. ?It?s a noticeable, maybe even impressive, event.?
Before Discovery docks at the space station, Sturckow will fly the ship through an orbital back flip to expose the thousands of heat-resistant tiles on its underbelly to astronauts inside the orbital laboratory. The station crew will take high-resolution photographs of the heat shield and send them to analysts on Earth for review.
The photo survey is part of a routine shuttle health check to make sure Discovery?s heat shield is in good shape after launch. NASA has kept a close eye on heat shield integrity since a hole in the wing of shuttle Columbia led to the loss its seven-astronaut crew in 2003.
Discovery?s astronauts inspected the shuttle?s wing edges and nose cap overnight Saturday as part of their standard shuttle health survey.
?Nothing stood out that I saw,? lead shuttle flight director Tony Ceccacci said early Sunday.
Cain said later on Sunday that analysts are still reviewing data from the inspection, as well as video and imagery from Discovery's launch. They are also awaiting the photographs of Discovery's underbelly from tonight's docking, he said.
Next stop: space station
Discovery?s six-man, one-woman crew will deliver a new crewmember and tons of science equipment and supplies for the six astronauts currently living aboard the space station during their mission. Astronaut Nicole Stott is riding Discovery to the station to begin a three-month mission to the station. She will replace NASA spaceflyer Tim Kopra, who has lived on the station for more than a month.
The astronauts are also delivering a new space treadmill named after television comedian Stephen Colbert.
Colbert won an online poll to name a new space station room after him, but NASA named it Tranquility instead. As a consolation prize, NASA dubbed the treadmill the Combined Operational Load Bearing External Resistance Treadmill, or COLBERT.
The treadmill launched in pieces packed away in a refrigerator-sized rack inside a cargo module in Discovery?s payload bay. Stott and her station crewmates won?t set up the COLBERT treadmill after an unmanned Japanese cargo ship, Japan?s first H-2 Transfer Vehicle, arrives at the station in mid-September.
Discovery will arrive at the space station on the 25th anniversary of its maiden launch on Aug. 30, 1984. That mission deployed three satellites and tested solar array technology for future space stations.
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SPACE.com is providing complete coverage of Discovery's STS-128 mission to the International Space Station with Managing Editor Tariq Malik in New York. Click here for shuttle mission updates and a link to NASA TV. Live docking coverage begins at 6:30 pm ET.