>>6920500 (lb)

For starting to get at the original trajectory of an object --

When an orbiting satellite re-enters the atmosphere, it's moving at about 7 km/sec (the speed needed to maintain an orbit), and it dissipates all that kinetic energy as it comes down through the atmosphere. Therefore, a satellite coming down is spectacular.

If an object was physically in space but not orbiting, just hovering there, it would fall directly down (like dropping a rock). There would be no crosswise motion, just downward descent. And while it could be going pretty fast by conventional standards, it would not have anywhere close to the extraordinary kinetic energy of a satellite, so it would not be as visible (would likely not glow with heat, for example.)

So just by seeing how a falling object from space moves and glows, it's possible to make a reasonable estimate of whether it was orbiting or not.

(The "not" category includes hovering via unconventional means, or a popup suborbital flight from a rocket that shoots straight up at relatively low velocity, like tossing a rock in the air but higher.)