KENNEDY SPACE CENTER, Fla. — The shuttle Endeavour closed out a grueling 16-day space station assembly mission with a smooth Florida landing on Friday, bringing Japan’s first long-duration astronaut back to Earth after four and one-half months in orbit.

Approaching from the south after a high-speed computer-orchestrated descent, the mission commander, Mark Polansky, took over manual control 50,000 feet above the Florida spaceport, banked to line up on runway 15 and guided the 110-ton shuttle to a picture-perfect touchdown at 10:48 a.m. Eastern time.

“Welcome home. Congratulations on a superb mission from beginning to end,” astronaut Alan Poindexter radioed from mission control in Houston. “Very well done.”

“Well, thanks to you and the whole team,” Polansky replied. “That’s what it’s all about. We’re happy to be home.”

Polansky and his shuttle crewmates — Marine Col. Douglas Hurley, the pilot; the Canadian flight engineer, Julie Payette; Dr. David Wolf; Dr. Thomas Marshburn; and Navy Cmdr. Christopher Cassidy — left Army Col. Timothy Kopra behind on the space station and brought Koichi Wakata back to Earth in his place.

Representing the Japan Aerospace Exploration Agency, Wakata was launched to the station aboard the shuttle Discovery last March. His stay at the lab complex was extended by a month when Endeavour’s launching was delayed from June 13 to July 15 by technical problems and bad weather.

As all returning space station astronauts do, he made the trip back to Earth resting on his back, in a recumbent seat on Endeavour’s lower deck, to ease the transition back to gravity.

Asked what he was looking forward to the most after reunions with family and friends, he listed fresh sushi, cold noodles and a visit to hot springs back home.

During a departure ceremony before Endeavour’s undocking from the station on Tuesday, the station commander — Gennady Padalka, a Russian cosmonaut — offered rare praise and “a special thanks to Koichi-san.” “He’s very dedicated and a very, very good flight engineer,” Padalka said. “As crew commander, I want to say we could rely on him in any situation.”

Among his scientific duties and routine maintenance chores, Wakata also tested bacteria-killing, water-absorbing Japanese underwear designed to be worn in space for weeks at a time.

“I wore them for about a month, and my station crew members never complained!” he said Thursday. “So I think the experiment went fine.”

Swapping out station crew members was just one of the goals of Endeavour’s mission.

Wolf, Marshburn and Cassidy, a Navy SEAL, staged five spacewalks, attaching an experiment platform to Japan’s Kibo lab module, replacing aging solar array batteries and storing critical spare parts.

The astronauts also rewired two of the station’s stabilizing gyroscopes, installed television cameras needed for the docking of a Japanese cargo ship in September, and deployed a jammed spare-parts mounting mechanism on the station’s main truss.

Only seven more shuttle flights remain before the fleet is retired next year, and NASA is launching as many spare parts to the station as possible to protect against future failures when smaller cargo ships may not be able to accommodate large components.

With Endeavour safely home, NASA will turn its attention to readying the shuttle Discovery for launch around Aug. 25 on a mission to deliver more supplies and equipment to the space station along with Kopra’s replacement, Nicole Stott.

Engineers are still assessing what caused an unusual amount of foam insulation to fall from the central section of Endeavour’s external tank during launch on July 15. Testing indicated that Discovery’s tank is in good shape, but additional checks were ordered on Thursday.

Assuming no problems are found, Discovery will be hauled to launch pad 39A on Monday.