FA-55852 / Astronomical coordinate conventions / Member archive

Polarization sky position angle: Linear polarization amplitude accidentally includes circular polarization · case 02

The adapter reports an incorrect linear power while other fields remain valid.

Member previewVariant 2 · 3 implementations · 6 checks per implementation

Case contract

Stokes Q,U rotate from instrument to sky with supplied c=cos(2theta),s=sin(2theta), so Qsky=cQ-sU and Usky=sQ+cU. Instrument mirror reverses U and V; I stays invariant. This model accepts exact supplied trigonometric values and does not infer astronomical angle zero points. Output fields are defined by: sky_q = d['c']*d['Q']-d['s']*d['U']; sky_u = d['s']*d['Q']+d['c']*d['U']; mirror_u = -d['U'] if d['mirror'] else d['U']; mirror_v = -d['V'] if d['mirror'] else d['V']; linear_power = d['Q']**2+d['U']**2; inverse_q = d['c']*d['Q']+d['s']*d['U']

Why this case matters

Catalog, detector, sky-coordinate, and spectroscopy adapters must preserve the association between numeric coordinates and their declared reference conventions.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
astronomical fixture 0	`{"inverse_q": 5, "linear_power": 45, "mirror_u": -5, "mirror_v": -2, "sky_q": -5, "sky_u": 4}`	`{"inverse_q": 5, "linear_power": 41, "mirror_u": -5, "mirror_v": -2, "sky_q": -5, "sky_u": 4}`	Failed

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