The International Space Station and the Space Shuttle Discovery which is currently attached to it were forced on Sunday to change orbit in order to avoid being hit by 10-year-old debris from a Chinese satellite launch.

The move was successful but made it the third time in three weeks the ISS has been threatened by orbiting space junk. Eleven days ago, the crew hunkered down in the Russian Soyuz capsule as a precaution against another piece of debris that passed by without incident.

Space debris is becoming an ever-increasing challenge. When it comes to dodging junk, it's a big deal. It's very tiring. Sometimes it's exhausting, said flight director Kwatsi Alibaruho.

The space junk was orbiting erratically and appeared to be about 4 inches in diameter, NASA said.

Mission control in Houston warned the astronauts of the debris before 3 p.m. C.T. and was expected to pass the space station repeatedly if NASA hadn't decided to change the station's position.

Had we not taken this action, the first time of closest approach would have been about two hours into Monday's spacewalk, NASA said in a news announcement.

The space junk includes discarded fuel tanks, screws, blots, paint chips, foil scraps and other objects. According to the Secure World Foundation estimates, there are also billions of bits and pieces smaller than one centimeter circling the planet, each following its own orbit.