CAPE CANAVERAL, Fla. - Endeavour and its six astronauts showed up at the International Space Station on Wednesday with the most expensive payload ever carried by a shuttle, a $2 billion magnetic device scientists hope will unravel the mysteries of the cosmos.

Shuttle commander Mark Kelly - the husband of wounded U.S. Rep. Gabrielle Giffords - carried out Endeavour's final docking. The lead flight director described the linkup as "really silky smooth" and noted Kelly has been performing "unbelievably" well in orbit.

Giffords was supposed to undergo surgery in Houston on Wednesday, two days after attending her husband's launch. Doctors planned to replace part of her skull with a plastic implant. She was shot in the head in early January during a political event in her hometown of Tucson, Ariz.

"If you didn't know any of that was going on, you wouldn't have any idea that those kinds of things are going on in his personal life," flight director Gary Horlacher told reporters. "The surgeons are keeping him informed appropriately."

Now that he's at the space station, Kelly can use the Internet-protocol phone there. He also has access to the Internet aboard the orbiting outpost, and can speak privately with NASA's flight surgeons via Mission Control whenever he wishes.

The two orbiting crews will attach the Alpha Magnetic Spectrometer to the space station Thursday.

Endeavour - making its final journey and the next-to-last flight of NASA's shuttle era - docked with the space station as the two vessels soared more than 200 miles above the planet, near Chile.

Kelly was the first to float into the space station. He was greeted with handshakes and hugs.

"Hey, you guys wore coordinating shirts," Kelly told the six space station residents, all dressed in blue polo shirts and tan slacks. "We didn't do that."

The combined crews include seven Americans, three Russians and two Italians.

The space station occupants rang the ship's bell to mark Endeavour's arrival. It is the 12th and final visit by Endeavour to the space station; after this mission, the baby of NASA's shuttle fleet will be decommissioned and sent to a museum in Los Angeles.

Atlantis will carry out the final shuttle trip in July.

Kelly and his crew will spend nearly two weeks at the space station. Their main job is to install the 7-ton Alpha Magnetic Spectrometer, an international collaboration representing 16 countries and led by Nobel-winning physicist Samuel Ting of the Massachusetts Institute of Technology.

At the heart of the spectrometer is a 3-foot, doughnut-shaped magnet. The instrument will seek out invisible dark matter as well as antimatter; whether any of this is found or not, the results will help explain what the universe is made of and how it formed.

As soon as the spectrometer is installed, it immediately should begin working. Ting expects to start receiving data within an hour or two.

The AMS will remain anchored to the space station for the rest of its life. The outpost will continue to operate until at least 2020.

Endeavour's crew also will unload spare parts for the space station and carry out four spacewalks, the first one scheduled for Friday.

Horlacher said he doesn't dwell on the fact that the AMS constantly seems to be overshadowed by attention on Kelly and Giffords.

"I know folks are kind of focused on Mark and his situation," he said. "But AMS is going to be around talking to us for a long, long time. So I'm very much looking forward to the results over the years."

For now, 12 astronauts are aboard the shuttle-station complex. On Monday, three of the six space station residents will climb into their Russian Soyuz capsule and return to Earth after a five-month stay. Endeavour's two-week launch delay resulted in the mission interruption.

NASA will continue to rely on Russia to transport U.S. astronauts back and forth to the space station for the foreseeable future. The space agency wants private companies in America to take over this operation, hopefully within a few years.

The Obama administration wants NASA focusing on interplanetary travel, once the shuttles are retired.