# Nodal period

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The nodal period of a satellite is the time between successive passages of a satellite through successive orbital nodes.[1][2] This applies to artificial, such as weather satellites, and natural satellites the moon. The nodal period of Earth's moon is 27.2122 days.[3]

## Near Earth-Satellites

The oblateness of the Earth has important effects of the orbits of near Earth-satellites.[4] 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:

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

## References

1. ^ "Glossary of Meteorology". American Meteorological Society.
2. ^ Nerem, Dr. R. Steven. "ASEN5050 Spaceflight Dynamics course slides". University of Colorado.
3. ^ Thompson, Richard (2003). Vedic Cosmography and Astronomy. Motilal UK Books of India. p. 12. ISBN 978-8120819542.
4. ^ King-Hele, D.G., 1958, The Effect of the Earth's Oblateness on the Orbit of a Near Satellite, Proceedings of the Royal Society of London. Series A, Mathematical and Physical, Vol. 247, No. 1248, pp. 49-72
5. ^ Blitzer, L., 1964, Nodal period of an earth satellite, AIAA Journal, Vol. 2, No. 8, pp. 1459-1460