US space shuttle Endeavour undocked on Sunday from the International Space Station and after a nine-day mission is heading back to Earth. 

The shuttle is scheduled to land Tuesday at NASA's Kennedy Space Centre on Cape Canaveral, Florida. The shuttle was previously scheduled to undock Monday from the ISS and to arrive on Wednesday in Florida.

According to NASA, the earlier landing opportunity was selected in the event Hurricane Dean threatens the Houston area. It allows an opportunity for the shuttle to land before Mission Control, Houston, would be shut down in preparation for a storm. Also the fourth spacewalk was reduced by two hours in order to allow the preparations for return.

According to NASA’s protocols, the STS-118 crew is conducting the post-undocking heat shield inspection. The seven astronauts will use Endeavour’s robot arm and a 50-foot-long Orbiter Boom Sensor System to inspect the nose cap and the leading edges of the wings. This process is conducted after undocking from the station to make sure the orbiter is ready for re-entry on landing day.

During their mission, the astronauts installed the Starboard 5 (S5) truss segment and transferred tons of cargo between the shuttle and the station. The STS-118 crew conducted four spacewalks at the station. The two major objectives were the installation of the S5 and the replacement of a failed attitude control gyroscope.

Late Thursday NASA mission managers in Houston decided not to repair the space shuttle Endeavour’s heat shield. "After hours of reviewing data and imagery collected during the inspections by the (shuttle) crew, the managers decided the damage did not pose a safety risk to the crew or Endeavour," a NASA statement said.

The damage is not enough to risk a catastrophic failure of the shuttle's heat shield, like the one that destroyed the shuttle Columbia on re-entry in February 2002, but the process of underside repairs during a spacewalk would have entailed risks for the astronauts.

Endeavour will bring home Barbara Morgan, the teacher turned astronaut, who during the mission responded to questions sent from students on Earth.

"Astronauts and teachers actually do the same thing. We explore, we discover and we share," she told during one the lessons. "Those are absolutely wonderful jobs."

Barbara Morgan’ association with NASA began more than 20 years ago. Initially Morgan was selected as the backup candidate for the NASA Teacher in Space Program on July 19, 1985.

From September 1985 to January 1986, Morgan trained with Christa McAuliffe and the Challenger crew at NASA’s Johnson Space Center, Houston, Texas. After the Challenger accident Morgan resumed her career as teacher, but she was selected by NASA as a mission specialist in January 1998.