President Obama called the crew aboard the Space Shuttle Atlantis and the International Space Station Friday to thank them and congratulate them on their mission, the final one in NASA's 30-year space shuttle program.

Obama joked with the combined 10-member crew that he thought he had been dialing out for a pizza and didn't expect to end up in space. The president told the astronauts they are an example not just to fellow Americans, but also to fellow citizens on earth. "I...want to just let everybody know how personally proud I am of you."

The 13-day mission comes to an end July 21. Upon its return, Atlantis will be retired and become an exhibit at the Kennedy Space Center. The president said the end of the program will usher in a new era to push the frontiers of space exploration and human space flight.

Obama has asked NASA to develop new systems that will be necessary to do things like send humans to Mars which he said "was no small feat" but added "I know we're going to be up to the task."

Atlantis commander Chris Ferguson told the president many people are working fervently toward these goals. "We sure hope to see some of our commercial partners climbing on board really soon...and we look forward to seeing them here..."

As part of Obama's plan for future U.S. space exploration, NASA will hire the services offered by commercial companies to fly its astronauts to and from the International Space Station. The president praised the space shuttle program for all its accomplishments in the last 3 decades. "You helped our country lead the space age," he told the crew members. "[A]nd you continue to inspire us."

The Atlantis crew plan to leave an American flag on the International Space Station, the same flag that was on board the first shuttle mission in 1981. Commander Ferguson says the flag will reside on the ISS until an American commercial space company launches astronauts to the station. "It will hopefully maintain a position of honor until the next vehicle launched from U.S. soil brings U.S. astronauts up to dock with the space station."