Cassini Laws -- from Eric Weisstein's World of Physics

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Cassini Laws

For a tidally locked body,

: 1. The rotation rate is synchronous with the mean orbital rate.
: 2. The spin axis maintains a constant inclination to the ecliptic plane. Eric Weisstein's World of Astronomy
: 3. The spin axis, orbit normal, and ecliptic normal remain coplanar.

References

Burns, J. A. (Ed.) Planetary Satellites. Tucson, AZ: University of Arizona Press, p. 104, 1977.

Kaula, W. M. An Introduction to Planetary Physics. New York: Wiley, p. 183, 1968.