FA-69489 / Orbital propagation / Member archive

Classical elements from a state vector: Semi-major axis loses the energy sign · case 04

Bound orbits report a negative semi-major axis.

Member previewVariant 4 · 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 [[-381.3488, -7970.4999, 2220.0855], [4.6015157, -1.3825381, -5.4145672], 398600.4418]	`[-9090.909, 0.1, 51.6, 100.0, 190.0, 330.0]`	`[9090.909, 0.1, 51.6, 100.0, 190.0, 330.0]`	Failed

MEMBER ARCHIVE

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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