The satellite that North Korea launched into space three years ago circles the earth every 95 minutes at an altitude of about 540 km (335 miles), its orbit decaying.
No signal has ever been detected from the crude-looking 100-kg (220-pound) hunk of black metal that the North said was mounted with cameras to take images and transmit them back to Pyongyang.
The North is planning another satellite launch next month, reigniting fears that it is really testing a system to deliver nuclear weapons. The secretive state is already under international sanctions for its nuclear and missile tests.