The U.S. space agency NASA is tracking a piece of Soviet space debris that could collide Tuesday with the International Space Station and the space shuttle Atlantis.

The debris will make its closest approach Tuesday, right in the middle of a planned spacewalk.

According to NASA officials the debris is from a Soviet era satellite and is one of 500,000 pieces of space debris the agency tracks.

The U.S. space shuttle Atlantis docked Sunday at the International Space Station .

Sunday's arrival marks the 12th and final visit by Atlantis to the space station.

The combined crew members, 10 in all, will begin more than a week of work, transferring a year's worth of supplies and equipment to the space station.

Upon its return to Earth next week, Atlantis will be retired and the 30-year U.S. space shuttle program will be over.

Charles Bolden, the administrator of the U.S. space agency NASA, told CNN television Sunday that he expects a new U.S.-made spacecraft to be ready to travel to the International Space Station by 2015. He said “not long after that” he hopes to see the U.S. leading a mission into deep space.

On Friday, an estimated crowd of 1 million people watched the historic final shuttle lift-off from the Kennedy Space Center in Florida.

NASA is ending the shuttle program to concentrate resources on deep-space exploration. The agency is working with several commercial U.S. aerospace companies to develop vehicles to replace the shuttles. Until then, Russia's Soyuz spacecraft will ferry U.S. astronauts to and from the ISS, while Russian, European and Japanese cargo spacecraft will continue their resupply and waste disposal missions to the station.

The four astronauts on Atlantis are Commander Chris Ferguson, Pilot Doug Hurley, Mission Specialist Rex Walheim and Mission Specialist Sandra Magnus. All four have flown on previous shuttle missions.