FA-69690 / Orbital propagation / Member archive

Cylindrical Earth shadow test: Sunward test assumes the sun is along +x · case 05

Satellites are shadowed on the day side when the sun is not on the x axis.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Input [r, s, R]: satellite position, sun direction (any length) and body radius. With u=s/|s| and d=r.u, the satellite is sunlit when d>=0; otherwise it is in umbra when the distance of r from the shadow axis |r-d u| is <= R. Return "umbra" or "sunlit".

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
cylindrical earth shadow test [[5000.0, 5000.0, 0.0], [-3.0, -4.0, 0.0], 6378.0]	`"sunlit"`	`"umbra"`	Failed

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