Space shuttle Discovery is seen docked to the International Space Station is featured in this image photographed by one of the STS-119 crewmembers during the mission's first spacewalk on March 19, 2009.
Astronauts aboard the International Space Station are packing up their spacecraft Wednesday as the shuttle Discovery prepares to head home after delivering new solar wings to the outpost.
Discovery astronauts will bid adieu to the International Space Station?s three-man crew and undock later today after a landmark eight days of construction to complete the orbiting lab?s power grid and backbone.
?We leave with a sense of accomplishment,? Discovery skipper Lee Archambault radioed Mission Control late Tuesday. ?It?s been a great docked timeframe and we look forward to what?s next.?
If all goes well, Discovery?s seven astronauts will get the glimpse of their orbital handiwork later this afternoon, when they undock from the space station at about 3:53 p.m. EDT (1953 GMT). Shuttle pilot Dominic ?Tony? Antonelli will be at the helm to guide Discovery in a victory lap while his crewmates snap photographs.
The astronauts delivered the space station?s fourth set of solar arrays, anchoring their 16-ton girder support to the outpost?s starboard side. With the addition, the station now has eight solar wings in all ? two per array - with four wings on each side.
?I think I should have time to enjoy the view if everything is working correctly,? Antonelli told reporters before flight. ?I?ll be right there at the window when that happens, so I?m looking forward to that.?
The new solar arrays boosted the station?s power grid by 25 percent, leaving the outpost capable of generating enough electricity to power a neighborhood of 42 average size homes. The space station will need that extra power to support its planned shift to six-person crews- double the current size - later this year.
?We want to thank you for bringing the space station up to full power,? Mission Control told the astronauts Tuesday.
Archambault and his crew launched March 15 on a 13-day mission to deliver the solar wings and a critical replacement part for the station?s urine recycling system to prime the station to support more science and larger crews. Both systems appear to be working well, and the astronauts will collect about four liters of water samples recycled through the urine processor later for the trip home.
Three spacewalks were performed by the astronauts, who spoke with U.S. President Barack Obama about their mission on Tuesday. They are expected to shut the hatches between Discovery and the space station at about 12:53 p.m. EDT (1653 GMT).
?I?d like to say that the crew of Discovery were the best houseguests we?ve ever had,? the station?s Expedition 18 commander Michael Fincke told Mission Control. ?Expedition 18 is very thankful to this great crew.?
Like the space station, Fincke?s Expedition 18 crew changed with Discovery?s arrival.
The shuttle brought up Japanese astronaut Koichi Wakata, Japan?s first long-term resident of the station, to join the Expedition 18 crew. Wakata replaced NASA astronaut Sandra Magnus, who is returning to Earth aboard Discovery after living in space for four months. He will join Fincke and Russian cosmonaut Yury Lonchakov for about a week and then stay aboard to serve aboard the next station crew, which is due to arrive on Saturday.
?It?s a bit sad that Sandy?s leaving and I?ll be saying goodbye to the [shuttle] crew,? Wakata radioed Mission Control Tuesday night. ?That?s a kind of sad feeling, but I?m also feeling ecstatic and looking forward to working with Yury and Mike.?
Wakata?s next crewmates, Expedition 19 commander Gennady Padalka of Russia and NASA astronaut Michael Barratt, are due to launch Thursday aboard a Russian Soyuz spacecraft with American billionaire Charles Simonyi, who is paying about $35 million for his second trip into space.
The new station crew is due to arrive at the space station on Saturday a few hours before Discovery is slated to land in Florida.
SPACE.com is providing continuous coverage of STS-119 with reporter Clara Moskowitz and senior editor Tariq Malik in New York. Click here for mission updates and SPACE.com's live NASA TV video feed. Live undocking coverage begins at 2:30 p.m. EDT (1830 GMT).
- Video - Meet the Expedition 19 ISS Crew
- Video - Discovery's STS-119 Night Launch
- Easy Skywatching: See the Shuttle and Space Station