Module elements 

State-vector to classical orbital element conversions.

Authoritative implementations of the standard two-body conversions between an inertial Cartesian state (ECI position and velocity) and the classical Keplerian elements; language bindings are thin marshaling layers over these functions.

• rv2coe - position/velocity to classical elements (Algorithm 9, Vallado 2022, pp. 113-116).
• coe2rv - classical elements to position/velocity (Algorithm 10, Vallado 2022, pp. 118-120).

Angle conventions

All angles in ClassicalElements are radians, normalized to [0, 2*pi) except inclination which lies in [0, pi]. The right ascension of the ascending node, argument of perigee, and true anomaly follow the Vallado reference conventions, including the canonical auxiliary outputs that resolve the degenerate elements of circular and equatorial orbits:

• argument of latitude (u = argp + nu) for circular inclined orbits, where the argument of perigee is undefined;
• longitude of perigee (lonper) for elliptical equatorial orbits, where the node is undefined;
• true longitude (truelon) for circular equatorial orbits, where both the node and the argument of perigee are undefined.

The auxiliary outputs that do not apply to a given orbit are returned as f64::NAN. coe2rv reads back whichever auxiliary angle the orbit type requires, so a ClassicalElements produced by rv2coe round-trips through coe2rv regardless of orbit type.

Structs

ClassicalElements

Classical (Keplerian) orbital elements in the Vallado convention.

Enums

ElementsError

Error returned by the classical-element conversions.

OrbitType

Geometric classification of a two-body orbit, which determines which of the classical elements are defined and which auxiliary angle resolves the degenerate ones.

Functions

coe2rv

Convert classical orbital elements to an inertial Cartesian state.

rv2coe

Convert an inertial Cartesian state to classical orbital elements.