HOUSTON--The shuttle Discovery glided to a picture-perfect docking with the International Space Station on Saturday, the veteran space plane's 13th and final linkup with the orbiting outpost.

With commander Steven Lindsey manually flying Discovery from the aft flight deck, the shuttle's payload bay docking system engaged its counterpart on the front end of the station's Harmony module at 1:14 p.m. CST.

"Station and Houston, Discovery has capture confirmed," an astronaut radioed.

The shuttle Discovery, docked to the International Space Station&39's forward port.

The historic linkup marked the first time in the station's 12-year history that spacecraft from the United States, Russia, the European Space Agency, and Japan were docked at the outpost at the same time.

Later in the mission, if all goes well and mission managers concur, three station crew members will undock in a Russian Soyuz spacecraft to photograph the lab complex and all the visiting vehicles from afar, capturing a unique moment that, with the shuttle's looming retirement, will never be repeated.

But first, the combined crews have to complete the primary objectives of Discovery's mission, including attachment of a final U.S. module, loaded with critical supplies and equipment, and an external storage platform carrying a spare set of radiator panels.

With the shuttle attached to the station, and with all of the visiting vehicles attached, the combined shuttle-station complex masses some 1.2 million pounds. It took longer than usual for relative motion between the two spacecraft to damp out, allowing the docking mechanism to firmly lock the shuttle in place, but it wasn't immediately clear if that was due to the mass of the vehicles or some other factor.

Station commander Scott Kelly (center, facing camera) looks on as the shuttle Discovery&39's crew enters the space station.

About 45 minutes later than planned, a final hatch between Discovery and the station was opened at 3:16 p.m., and 20 minutes after that, Expedition 26 commander Scott Kelly, along with Alexander Kaleri, Oleg Skripochka, Dmitry Kondratyev, Catherine Coleman, and Paolo Nespoli welcomed Lindsey and his shuttle crewmates--Eric Boe, Al Drew, Stephen Bowen, Michael Barratt, and Nicole Stott--into the space station.

After a mandatory safety briefing, the flight plan called for the shuttle astronauts to press ahead with work to transfer spacesuits and other gear to the station.

Barratt and Stott, operating the station's robot arm, planned to pull a cargo pallet out of Discovery's cargo bay. The pallet, known as external logistics carrier No. 4, is loaded with a spare set of radiator panels for the station's ammonia cooling system.

ELC-4 will be mounted on the underside of the station's right-side solar power truss. To get it there, Barratt and Stott will hand it off to the shuttle's robot arm, operated by Boe and Drew.

The station arm then will be repositioned, inchworm fashion, moving from the Harmony module to its mobile base workstation. When the move is complete, the shuttle arm will hand ELC-4 back to the station arm and the pallet will be mounted on the solar power truss for future use as needed.

Because it took longer than expected to complete the docking procedure, the actual attachment of the cargo pallet may be deferred to Sunday.

The shuttle Discovery performs a backflip maneuver during approach to the International Space Station, allowing the lab crew to photograph its heat shield.

Lindsey and Boe began the terminal phase of the rendezvous at 10:33 a.m. with a rocket firing to begin closing the final 9.2 miles to the station.

Just after 1 p.m,. with the shuttle poised 600 feet directly below the lab complex, Lindsey guided Discovery through a routine-but-still-spectacular end-over-end backflip maneuver, allowing the station crew to photograph the orbiter's heat shield.

Working in the Russian Zvezda command module, Coleman and Nespoli photographed Discovery's heat shield, using 400mm and 800mm telephoto lenses respectively, as the orbiter flipped about. The images will be downlinked to analysts in mission control at the Johnson Space Center here for detailed evaluation.

During Discovery's launching Thursday, several pieces of foam insulation fell away from the ship's external tank, including some that appeared to contact the shuttle's heat shield. The foam shedding occurred well after the first 2 minutes and 15 seconds of flight when the dense lower atmosphere can cause debris to hit with a high relative velocity.

Engineers do not believe the foam lost Thursday caused any significant damage, and nothing out of the ordinary could be seen in television views of the maneuver. But the photos taken by Coleman and Nespoli will be carefully scrutinized to make sure.