- Eccentricity vector
In
astrodynamics , the eccentricity vector of aconic section orbit is the vector pointing towards theperiapsis and with magnitude equal to the orbit's scalar eccentricity. The magnitude isunitless .Calculation
The eccentricity vector can be calculated from the
orbital state vectors and at any time (the result is constant)::where:
* is velocity vector of theorbital state vectors ,
* is position vector of the orbital state vectors,
* isstandard gravitational parameter .Alternatively it can also be computed from
orbital angular momentum vector ::where:
* isorbital velocity vector ,
* isorbital angular momentum vector ,
* isorbital position vector ,
* isstandard gravitational parameter .Since is defined as , it can be shown by the vector
triple product identity that this formula is equivalent to the one above.ee also
*Eccentricity
*Orbit
*Laplace-Runge-Lenz vector
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