Kepler Third Law Calculation  

Planet Mass :
M = 4 ∏^{2} r^{3}/GT
Where,
G = Universal Gravitational Constant = 6.6726 x 10^{11}Nm^{2}/kg^{2}
r = Satellite Mean Orbital Radius
M = Planet Mass
Example:
Calculate planetary motion, Satellite Orbit Period for the given details.
Satellite Mean Orbital Radius(r) = 25 m
Planet Mass (M) = 15 kg
Solution:
Apply Formula:
T = √(4∏^{2}r^{3}/GM)
T = √(4*3.14^{2}*25^{3}/6.6726 x 10^{11}Nm^{2}/kg*15
T = 24813343.69 s
Satellite Orbit Period (T) = 24813343.69 s