Technical
Ballistic Coefficient
A measure of how strongly atmospheric drag affects a spacecraft, combining its mass, cross-sectional area, and drag coefficient.
The ballistic coefficient expresses a body's ability to overcome air resistance: a higher value means the object is denser relative to its frontal area and decelerates less from drag.
In low Earth orbit it strongly influences orbital lifetime and reentry behaviour. Low-ballistic-coefficient objects (and deployable drag devices) decay faster, which is exploited for post-mission disposal; predicting reentry time depends heavily on this parameter and on space weather.