HOUSTON Atlantis crew members threw open the doors to the International Space Station (ISS) late Monday and began the process of moving equipment and supplies into the orbital outpost this morning.

Commander Terry Wilcutt and mission specialist Ed Lu opened the first of 12 hatches in the station Monday at about 10:47 p.m. Eastern Daylight Time (Tuesday, 02:47 GMT) to start the process of sampling air and placing air ducts to improve the ventilation inside the 143-foot- (42.9-meter-) long structure.

Early Monday morning Lu and cosmonaut Yuri Malenchenko made a spacewalk to install cables and attach a boom to a magnetometer. Later, Atlantis fired its thrusters in the first of three attempts to boost the station into an orbit about 230 miles (370 kilometers) above Earths surface.

Atlantis lifted off Friday from Kennedy Space Center on an 11-day mission to deliver supplies and make the space station ready for its first occupants, set to arrive this fall.

At about 01:50 a.m. EDT (05:50 GMT) Tuesday, Wilcutt and Malenchenko opened the hatch, entered the Russian-built service module and shook hands. The crew briefly wore safety glasses and dust masks as precautions against dust and dirt that might have been stirred up in the stations newest module.

"We see a good view of the service module," said astronaut Rex Walheim from Mission Control. "There are a lot of people smiling down here"

"Same here," Wilcutt replied. "Its absolutely beautiful."

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The shuttle commander and veteran Mir cosmonaut were the first to enter the module since it was launched July 12 from the Baikonur Cosmodrome in Kazakhstan. The module will provide living quarters for space station crews.

Wilcutt reported a comfortable 79 degrees Fahrenheit (26 degrees Celsius) and 42-percent humidity inside the service module as the crew set to work.

The crew also entered the Russian-built Progress supply ship docked to the aft end of the service module. More than 1,300 pounds of supplies to outfit the service module will be transferred to the station. Additionally, the Progress carries liquid propellant for the stations attitude control system.

Atlantis commander Terry Wilcutt and cosmonaut Yuri Malenchenko wear breathing masks as they work through their checklists inside the Zvezda service module Tuesday morning in this image from NASA TV.

Before the crew moved equipment into the station from the orbiter or the Progress, items no longer needed such as the service modules docking probe and equipment along with launch restraints and hardware and were moved for return to Earth.

Late Tuesday evening, the crew will install three batteries in the service module and swap another in the Zarya module.

Office supplies, repair parts and hygienic items are included on the Progress manifest for unloading. Among the gear to be delivered and installed from the Spacehab module aboard Atlantis include clothing, medical kits, laptop computers and critical life-support equipment such as oxygen generators and carbon-dioxide scrubbers.

Cosmonaut Boris Morukov supervises unloading the Progress this morning while mission specialist Rick Mastracchio will oversee the unloading of the more than 8,000 pounds (3,600 kilograms) from the Spacehab module.

"Well have checklists of all the items that we plan on carrying into orbit with us," Mastracchio said. "At the end of each day were going to get together with the ground controllers and compare notes and lists and make sure that, if I sent an item over to the station, Dan Burbank got it and stowed it where it needed to be."

Mission specialist Burbank makes sure each item goes to the right place in the cramped confines of the station so future crews or occupants can find it. Items moved into the station are tagged with their identity and where they should be stowed.

Shuttle Atlantis will remain in space one more day than planned thanks to the conservation efforts of the seven-member crew, NASA managers announced this morning.

Landing is now scheduled for September 20, one week from tomorrow.

Any tasks not completed by the time Atlantis undocks will likely fall to the stations first crew, since the next shuttle mission to the station already has a full agenda.

Space Shuttle Discovery and a seven-person crew are set to be the next visitors to the station after an October 5 liftoff. During their flight, the crew will make four spacewalks to deliver and install the Z-1 truss which houses gyroscopes and an antenna. The stations first permanent crew, consisting of astronaut Bill Shepherd and cosmonauts Sergei Krikalev and Yuri Gidzenko, will fly aboard a Soyuz launched from the Baikonur Cosmodrome in late October.