Orbital Constants

A satellite of mass $m$ is orbiting a planet of mass $M$ at a distance $R$ of the planet's centroid. If $\Gamma$ is the Potential Energy of the satellite, and its Kinetic Energy can be written as $\alpha \Gamma$ , $\alpha$ a real constant, then the correct value of ${ \alpha }^{ -2 }$ is:

$Details$ : Consider that the satellite's dimensions are suffiently small and that the planet is sufficiently spherical, homogeneous and distant from the satellite. Assume that $G$ as the Gravitational Constant