The orbital inclination or inclination of a celestial body is in the celestial mechanics of the angle between its orbital plane and a reference plane.
The orbital inclination is one of the six orbital elements of the classical orbit determination and will almost always denoted by i ( for " inclination "). Together with the argument of the node defines the position of the plane of the web in space.
- For reference, the plane of Earth's orbit ( the ecliptic ) is selected in the solar system usually differ by only a few degrees from the orbits of the major planets and the moon.
- For artificial earth satellites is chosen as the reference of the satellite orbit elements, the mean equatorial plane of the earth, just as for the orbital motion of binary stars. It is in the latter mostly as a position angle of the major railway axis - specified - relative to the equatorial coordinate system (RA, δ ). Webs with a dip angle of 90 ° hot polar orbits.
- The inclinations of the planets nearby moons of the other planets of the solar system relative to the equatorial plane of the orbiting planet. The inclination of the more distant moons, however, is again measured with respect to the ecliptic. The only exception is the large Saturn's moon Iapetus, whose inclination is given regarding its Laplace plane.
- The inclination of an orbit in a multiple star system, or an exoplanet is measured against a direct line of sight perpendicular to the plane standing. Thus mean inclination = 0 °, we see that the system directly from the top, so the Bahnpol points to the observer, while inclination = 90 ° means that we see the orbital plane directly from the edge.
- Orbital inclinations between 90 ° and 270 ° indicate a retrograde ( opposite ) orbit.
In the case of Kepler paths ( only two bodies in a vacuum), it is constant and the plane of the web remains in its orientation in the fixed stars stable. In gravitational third-body perturbations, the argument of the node suffers small partially periodic changes. Therefore, the path element is specified as a series oskulierender terms with respect to a period, so as at any given time valid approximate solution.