Standard gravitational parameter

The standard gravitational parameterμ of a celestial body is the product of the gravitational constantG and the mass M of that body. For two bodies, the parameter may be expressed as G(m₁ + m₂), or as GM when one body is much larger than the other: $${\displaystyle \mu =G(M+m)\approx GM.}$$

For several objects in the Solar System, the value of μ is known to greater accuracy than either G or M. The SI unit of the standard gravitational parameter is m⋅s. However, the unit km⋅s is frequently used in the scientific literature and in spacecraft navigation.