China's defunct Tiangong 1 space station hurtled toward Earth on Sunday and was expected to re-enter the atmosphere within hours.
Most of the craft should burn up on re-entry, so scientists said it poses only a slight risk to people on the ground.
The European Space Agency forecast that the station, whose name translates as "Heavenly Palace," will re-enter sometime between Sunday night and early Monday GMT. The Chinese space agency said it should happen during the course of Monday Beijing time.
The Aerospace Corp. predicted Tiangong 1's re-entry would take place within 2 hours of either side of 0010 GMT Monday (8.10 p.m. Sunday EDT.)
Based on the space station's orbit, it will come back to Earth somewhere 43 degrees north and 43 degrees south, a range covering most of the United States, China, Africa, southern Europe, Australia and South America. Out of range are Russia, Canada and northern Europe.