FA-69483 / Orbital propagation / Member archive

Classical elements from a state vector: Eccentricity vector adds the radial-velocity term · case 03

Eccentricity and perigee direction are wrong away from the apsides.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Input [r, v, mu] (km, km/s) for an inclined, eccentric orbit. Return [a, e, i, raan, argp, nu] with a rounded to 3, e to 6 and angles in degrees rounded to 4, using the node vector n=[-h_y,h_x,0], eccentricity vector ((v^2-mu/r) r - (r.v) v)/mu and quadrant rules raan>180 when n_y<0, argp>180 when e_z<0, nu>180 when r.v<0.

Why this case matters

Orbit determination and mission planning chain many small conversions; one wrong branch or unit silently moves a spacecraft by kilometres.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
classical elements from a state vector [[4456.1689, -4211.3181, -12476.7753], [1.3065909, -3.3947954, 4.0262806], 398600.4418]	`[14285.714, 0.421415, 98.0, 300.0, 231.8818, 296.8818]`	`[14285.714, 0.4, 98.0, 300.0, 45.0, 250.0]`	Failed

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