B^*

The B-Star Drag Term is used for the SGP4 type propagator and estimates the effects of atmospheric drag on the satellite's motion. It is defined by the following equation:

B^* = C_Dr₀A / 2m

where     B^*  = The B-Star Drag Term;
               C_D = The Coefficient of Drag;
               r_o  = The Atmospheric Density;
                A  = The Cross-sectional Area of the Satellite; and
                m = The Mass of the Satellite.

The units are EarthRadii^-1.

The format of the B-Star Drag Term in a TLE is as follows:

Sign: (nil or -): The sign of the B-Star Drag Term. No sign indicates positive;
First five digits: A number with a decimal point assumed to precede the first digit;
Sign (nil or -): The sign of the exponent. No sign indicates positive; and
Last digit: The exponent (base 10).

The ISS B-Star Drag Term "97127-4" translates to a B-Star Drag Term of +0.97127x10^-4 EarthRadii^-1 or in scientific notation:

+9.7127x10^-5 EarthRadii^-1.

Not all propagators read or use this value.