Theoretical bounds for estimating the ballistic coefficient of a ballistic object during the re-entry phase have been addressed. One essential characteristic of the vehicle trajectory is its deceleration when it reaches dense atmospheric layers. The intensity of the phenomenon is proportional to a scalar, called the ballistic coefficient. This leads to an highly nonlinear time-varying dynamic. To understand the dimensioning parameters for estimating the ballistic coefficient, accurate approximations of the Fisher information matrix are developed. The main result is a closed-form expression of a lower bound for the variance of the ballistic coefficient estimate.Notations † Let S be the object cross-section, C X its drag coefficient and M its mass, † the ballistic coefficient b is the product C x S/m and is expressed in m 2 kg 21 , † go ¼ 29.8 ms 22 is the gravitational acceleration (at ground level), † alt is the altitude; alt W y in the coordinate system of the