Before space shuttle Atlantis' encounter with the international space station Sunday, astronauts took more photographs of a section of peeled-back thermal blanket on the spacecraft.
NASA engineers are focusing their attention on a gap about 4 inches (10 centimeters) by 6 inches (15 centimeters) that was discovered after Friday's launch from Kennedy Space Center.
Engineers were not sure if stitching on the blanket came loose or if the blanket, covering a pod of engines near the shuttle's tail, was hit by debris during launch.
Prior to Atlantis' arrival at the space station, 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 (183 meters) below the orbiting outpost.
The pictures were taken when Atlantis commander Rick Sturckow maneuvered the shuttle into a 360-degree back-flip - part of an inspection technique. Engineers want to make sure there is no damage from launch like the kind that doomed Columbia in 2003.
Atlantis was scheduled to dock with the space station at 3:38 p.m. EDT (1938 GMT) Sunday. It was to be the first visit by a shuttle to the space station this year.
Soon after docking, U.S. space station resident Sunita Williams and shuttle astronaut Clayton Anderson will trade out seatliners on the Russian emergency vehicle attached to the station. The seatliner exchange marks the official replacement of Williams by Anderson as a space station resident.
The shuttle astronauts' wake-up song Sunday, "Riding the Sky," written by two Johnson Space Center employees, was dedicated to Anderson in honor of his move to the space station.
Williams will return to Earth aboard Atlantis after more than six months in space.
NASA engineers want to study more photos of the torn blanket, including images taken by cameras attached to the solid rocket boosters that separated from Atlantis after launch.
On Saturday, astronauts took photographs of the thermal blanket and heat shield using a camera attached to the end of a robotic arm and boom.
Engineers can build models from the images and perform tests to determine if the peeled-back blanket would be problematic when Atlantis returns to Earth.
Thermal blankets came unstitched during flights of Discovery in 2005 and 2006 with no problems, and thermal tiles were lost in the same area where the blanket is on Atlantis on two of the earliest shuttle flights.
The area does not get hotter than 1,000 degrees Fahrenheit (538 Celsius) during the shuttle's re-entry, compared with other vehicle parts, where temperatures can reach 2,900 degrees Fahrenheit (1,593 Celsius).
If the blanket needs to be fixed, Atlantis' astronauts could trim it off, tuck it back into protective tiles or cover it with a plate held in place by adhesive goo during three planned spacewalks or an extra one that could be added.
After the Columbia disaster, a shuttle repair kit was included in all shuttle missions.
During the 11-day mission, Atlantis will also deliver to the station a new segment, which includes a third pair of solar arrays. The new addition was expected to be attached to the station Monday during the first spacewalk.