Space shuttle Atlantis' crew spent Saturday inspecting the craft's heat shield for damage as they prepared to pay the last visit to the International Space Station in U.S. space shuttle history.

It was the first full day in space for Atlantis' four-member veteran crew after blasting off from the shuttle's space port in Florida on Friday. About one million sightseers witnessed the milestone in the 30-year history of the U.S. shuttle program.

We have been determined to finish strong and this was a great beginning, said LeRoy Cain, deputy shuttle program manager.

Atlantis is scheduled to dock on Sunday at the space station, a $100 billion project of 16 nations that took more than a decade to build 230 miles above Earth.

The ship is scheduled to spend about a week at the station, transferring more than 5 tonnes of food, clothing, science experiments and other gear to the station and packing up old equipment to be returned to Earth.

The crew used Atlantis' robot arm to inspect heat-resistant tiles on the shuttle's nose and wings on Saturday. The inspections have been required on every mission since 2003, when shuttle Columbia broke apart as it returned to Earth, killing all seven crewmembers.

NASA engineers will spend a few days studying the data before giving Atlantis' heat shield a clean bill of health. But there are no obvious anomalies and the vehicle is extremely clean, Cain said.

NASA limited the number of astronauts on the final shuttle flight to four, rather than the six or seven typically assigned. That will accommodate the smaller Russian Soyuz capsules that will serve as the Atlantis crew's lifeboats.

NASA originally planned for Atlantis to land on July 20, but could add an extra day to the mission if shuttle supplies allow, Cain said.

NASA is ending the shuttle program mainly due to high operating costs. Its legacy includes launching and servicing the Hubble Space Telescope and dispatching dozens of planetary probes and Earth-orbiting satellites. But the program also has a troubled safety record.

(Editing by Christopher Wilson)