KENNEDY SPACE CENTER, Fla.--With pilot Kevin Ford at the controls, the shuttle Discovery undocked from the International Space Station on Tuesday after delivering a fresh crew member and more than 18,500 pounds of needed equipment, supplies, and fresh water.
"Houston and station, from Discovery, physical separation," an astronaut radioed at 3:26 p.m. EDT as powerful springs in the station's docking mechanism gently pushed the shuttle away as the two spacecraft sailed 220 miles above central Asia in orbital darkness.
Undocking came eight days, 19 hours and 32 minutes after commander Frederick "C.J." Sturckow guided Discovery to a linkup with the space station a week ago Sunday.
For undocking, Sturckow and the rest of the shuttle crew--flight engineer Jose Hernandez, John "Danny" Olivas, Patrick Forrester, European Space Agency astronaut Christer Fuglesang, and returning space station flight engineer Timothy Kopra--assisted Ford as he carefully guided Discovery away.
Kopra was replaced aboard the station by astronaut Nicole Stott, who hitched a ride to the lab complex aboard Discovery. She plans to remain aboard the station until November when another shuttle crew delivers more supplies and equipment.
Ford guided Discovery through a three-quarter-lap fly around, looping up and over the outpost for photo-documentation survey of the outpost before departing the area around 5:10 p.m.
"We'd like to extend our thanks to the Expedition 20 crew for all their great support and assistance during the docked mission," Sturckow radioed the station crew. "Thanks especially to Gennady (Padalka, the commander) ... for your great work."
"C.J., thanks so much to you and the whole STS-128 crew and thanks to (lead Flight Director) Heather Rarick and all the ground teams that brought the good ship Discovery to us," flight engineer Michael Barratt replied from the station. "We're pretty fat with supplies now, thanks to you, and we're in better shape to carry on the work that we're here to do. You guys have a safe trip home, Discovery, it was great hosting you."
Shuttle pilots normally use smaller vernier jets, two in the nose and four in the tail, when maneuvering near the station. But one of Discovery's forward verniers suffered a leak shortly after launch, prompting flight controllers to close a shared propellant manifold that took out both forward jets. That action disabled the vernier system for the duration of the fight.
NASA engineers approved an alternate digital autopilot, or ALT-DAP, technique for using the the shuttle's more powerful primary reaction control system jets to reorient the shuttle-station complex for undocking and for carrying out the fly around. Procedures were put in place to make sure no thruster plumes hit the station's delicate solar arrays.
Sturckow successfully used the big jets for docking and Ford had no problems with the undocking and fly around.
"It should be a real thrill," Ford told CBS News before launch. "The exciting part starts when we get to a certain range, maybe about 400 feet, I'll do some ups and we'll start a maneuver that takes the orbiter up and over the top of the space station and we'll do this full 360-degree fly around at about 650 feet.
"It's a great range, it's far enough away that the jets don't really impinge on station and it's also a good range for photography and a chance for us to take a lot of photos of the exterior of the station for documentation. And of course, sometimes the station gets some pictures of the orbiter flying around it. It'll be really spectacular."
Following the fly around, the shuttle crew turned its attention to a final heat shield inspection, using a laser scanner on the end of a 50-foot-long boom to look for any signs of damage to the shuttle's reinforced carbon carbon nose cap and wing leading edge panels.
The so-called "late inspection" is identical to a procedure carried out the day after launch to look for signs of ascent impact damage. This time around, engineers were looking for any signs of damage from orbital debris or micrometeoroid impacts that might have occurred since the initial inspection.
There were no immediate signs of any problems, but it will take engineers at the Johnson Space Center in Houston another day to complete their analysis.
The astronauts plan to spend the day Wednesday packing up and testing the shuttle's re-entry systems. Landing back at the Kennedy Space Center is targeted for 7:05 p.m. Thursday, weather permitting.