J2 (computed)

The `J_2` constant is the Earth's second dynamic form factor used in computing the `J_2` perturbation of the inverse square formulation of the gravitational effect on the force due to a perfect spherical body of uniform density.

The MATH AND SCIENCE

This factor can be calculated as:

`J_2 = (2 epsilon_E/3) -  (R_E^3 omega_E^2) / (3 G M_E)`

where

• `epsilon_E` is the central body's oblateness (in this case Earth's oblateness)
• `R_E` is the central body's equatorial radius (in this case the Earth's mean equatorial radius)
• `omega_E` is the central body's rotational rate (in this case Earth's rotation rate is `7.292115 X 10^-5` rad/sec
• `G` is the universal gravitational constant
• `M_E` is the mass of the central body (in this case the Earth's mass)

REFERENCE

Equation section of Nodal Precession article

SEE ALSO

• J2 Perturbation Force
• Non-spherical Earth Perturbation - RAAN (combined coefficients)
• J2 (constant)