CAPE CANAVERAL, Florida - Astronauts aboard space shuttle Endeavour tested their ship's landing systems in preparation for an early Wednesday touchdown at the Kennedy Space Center.

Backdropped by a night time view of the Earth and the starry sky, the Space Shuttle Endeavour is seen docked to the International Space Station in this photo provided by NASA and taken on May 28, 2011. [Photo/Agencies]

The scheduled 2:35 am EDT landing will bring an end to Endeavour's 19-year flying career, the second of NASA's three shuttles to be retired.

NASA plans to close out its 30-year-old shuttle program with a final supply run to the International Space Station aboard Atlantis in July.

"The space shuttle has been the workhorse of the US space program for better than 30 years now, so it'll be sad to see it retired," Endeavour commander Mark Kelly said during an in-flight interview late Monday.

"But we are looking forward to new spacecraft and new destinations and we're all excited about the future," he added.

NASA is retiring the shuttles due to high operating costs and to free up funds to develop new spacecraft that can travel beyond the space station's 220-mile/346 km high orbit where the shuttles cannot go.

Kelly and his five crewmates - pilot Greg Johnson, flight engineer Roberto Vittori with the Italian Space Agency and spacewalkers Drew Feustel, Mike Fincke and Greg Chamitoff - are wrapping up a successful 16-day mission to complete assembly of the US part of the station, a $100 billion project of 16 nations.

International effort

Station construction began in 1998, and crews have been living aboard the outpost continuously since November 2, 2000.

The United States' decision to retire the shuttles without have a replacement ship ready has drawn sharp criticism, including a public rebuke from Apollo 11 commander Neil Armstrong, the first person to land on the moon.

Kelly acknowledged it will be at least four years before NASA astronauts can fly out of the United States again. Until new ships are ready, Russia will transport crews to the station, at a cost of more than $50 million per person.

"It will be a challenging transition, but I expect great things," Kelly said.

Endeavour returns with a new record-holder aboard: Fincke, who previously served two long-duration missions on the space station, will have spent 381 days in space - more than any other US astronaut.

Russia, which flew a series of space stations before partnering with NASA in the international endeavor, dominates the space endurance record books. Top on the list is cosmonaut Sergei Krikalev, who flew six missions on the Soviet-era Mir space station, two shuttle missions and two stints on the International Space Station, for a total of 803 days in space.

"I hope my record is soon broken," Finke said.

The primary goal of Endeavour's flight, the 134th in shuttle program history, was to deliver the station's premier science experiment, the $2 billion Alpha Magnetic Spectrometer particle detector. The crew also conducted four spacewalks to prepare the outpost for operations after the shuttle program ends.