Nodal period

The nodal period of a satellite is the time between successive passages of a satellite through successive orbital nodes. This applies to artificial, such as weather satellites, and natural satellites the moon. The nodal period of Earth's moon is 27.2122 days.

Near Earth-Satellites

The oblateness of the Earth has important effects of the orbits of near Earth-satellites. An expression for the nodal period ($T_n$) of a near circular orbit, such that the eccentricity (ε) is almost but not equal to zero, is:

$T_n = \frac{2\pi a^{\frac{3}{2}}} {\mu^{\frac{1}{2}}} \left[ 1 - \frac{3 J_2 (4 - 5\sin^2 i)}{4(\frac{a}{R})^2 \sqrt{(1-\epsilon^2}(1+\epsilon \cos\omega)^2} - \frac{3 J_2 (1 - \epsilon\cos\omega)^3}{2(\frac{a}{R})^2 (1-\epsilon^2)^3} \right]$