As I understand it, most decaying satellites circularise their orbits before burn-up. This produces long duration fireballs that last over a minute and cover very long ground tracks of several hundreds of kilometers. Whilst solar-system debris can collide with the atmosphere tangentially, this is a relatively rare event and few meteoric fireballs would last more than about 30 seconds. The vast majority lasting under 10 seconds. Velocity is not a good discriminant to the visual observer, as the decaying satellite is moving at 8 km/sec, whereas the SLOWEST entry velocity for a meteoric object is 11 km/sec. Although velocities of over 70 km/sec are possible, most of the LARGE debris that causes meteoric fireballs is in low inclination direct orbits which catch up with the Earth from behind. This is the reason for the excess of slow moving evening meteoric fireballs over faster moving morning objects (that are met head on). Due to the problems in discriminating the lower velocity fireballs on angular motion alone, and as the higher velocity objects must have short durations, it would seem that the duration of the event may be the best discriminant. Without any firm data, I would suggest a duration of around 30 seconds could separate the vast bulk of re-entries from meteoric fireballs. Over a period of a decade or so some friends and I operated all-sky cameras for recording fireballs. We recorded over 50 events brighter than about mag -6, but only one event was known to be a satellite re-entry. This event passed from horizon to horizon with a maximum elevation of some 40 degrees. In terms of its angular path across the sky (and thus duration) it stood out dramatically from all the other trails. Of course, if it is possible to calculate the trajectory and velocity from observations, the nature of the event should be fairly clear. I would be interested to know what sort of fireball durations have been produced be re-entring debris of various sizes and at what heights they typically start to burn and extinguish. I guess this is well documented for the Shuttle. Cheers, Rob McNaught rmn@aaocbn2.aao.gov.au