Scientists say that they will be able to give about 8 hours warning before it crashes as to an approx location
The 20-year-old Upper Atmosphere Research Satellite is expected to break into 100 pieces, many of which will burn on re-entry.
But scientists said 26 pieces - some weighing up to 135kg - are expected to survive. The debris could be scattered over an area about 800km long
Now for the waiting game



