Amidst greetings, hugs and handshakes with the 11-member Shuttle Atlantis Crew, who arrived at the orbiting outpost, Indian American astronaut Sunita Williams wrapped up her six-month long tour of duty as a station crew member by switching places with Mission Specialist Clayton Anderson.

However, amid the smiles and salutations, questions remained unanswered about a section of peeled-back thermal blanket on the shuttle.

Engineers continued to review photographs of the affected area to determine whether it could pose a problem when Atlantis returns to Earth.

NASA [Images] is taking no chances after the Colombia disaster in February 2003, when Indian-born astronaut Kalpana Chawla and six other crew members perished mid-air. The shuttle disintegrated on re-entry to earth when a protective foam tile shook loose and a hole burned into the shuttle's body.

NASA engineers are focusing their attention on a gap about 4 inches by 6 inches that was discovered after Friday's launch from Kennedy Space Center.

Engineers were not sure whether stitching on the blanket came loose or whether the blanket, covering a pod of engines near the shuttle's tail, was hit by debris during launch.

Prior to Atlantis' arrival, the astronaut Danny Olivas took additional photographs from inside the shuttle of the area where the thermal blanket had peeled back. The images were sent to Mission Control for analysis.

Astronauts inside the space station also took photographs of the shuttle's belly when Atlantis was 600 feet below the orbiting outpost.

The rest of the vehicle appeared to be in fine shape, NASA said.

Sensors reported six hits on the wing during launch, but engineers were not concerned. After the Columbia disaster, a shuttle repair kit was included in all shuttle missions.

Hatches between the two spacecraft opened about one-and-a-half hours after the shuttle docked with the space station.

"Atlantis arriving," Sunita Williams, said after the traditional ringing of a bell. Atlantis' astronauts floated into the space station's Destiny laboratory and hugged each of the station's residents, which includes the commander, Fyodor Yurchikhin, and the cosmonaut Oleg Kotov.

After a busy Sunday at the International Space Station [Images], attention has turned to the mission's first spacewalk. The excursion, which will focus on the on-orbit assembly of the station, is slated to begin at 1:53 pm EDT Monday.

Space Shuttle [Images] Atlantis and the STS-117 crew arrived at the station on Sunday at 3:36 pm EDT, delivering a new truss segment and crew member to the orbital outpost. The STS-117 crew entered the station for the first time after the hatches between the shuttle and station opened at 5:04 pm.

The STS-117 astronauts quickly jumped into joint operations with the station's Expedition 15 crew. The crews also began preparations for Monday's installation of the Starboard 3 and 4 (S3/S4) truss segment and the spacewalk.

The crews used the shuttle robotic arm to lift the S3/S4 out of Atlantis' payload bay and to hand it off to the station arm.

The S3/S4, which contains a new set of solar arrays, is scheduled to be attached to the station prior to the start of the spacewalk conducted by STS-117 Mission Specialists John 'Danny' Olivas and Jim Reilly.      

Olivas and Reilly are spending the night in the station's Quest Airlock in preparation for the spacewalk.