Comment Re: ballistic decay (Score 3, Informative) 33
A contradiction in terms, since something ballistic is implied to be acted on only by gravity and will not decay.
There is something called the "ballistic coefficient" (bstar in TLE speak) that, while also a contradiction in terms, refers to the drag coefficient multipled by the area-to-mass ratio of the object in orbit.
The decay of an object in the lower reaches of low earth orbit is dictated by the product of atmospheric density with the ballistic coefficient. A dense brick will last longer than a large sail of the same mass in the same orbit.
"Ballistic decay" is the above simplification simplified further by the well-known phb method.