FA-56097 / Astronomical coordinate conventions / Member archive

Heterodyne sideband coordinate: Sky-to-IF inverse mapping drops the sideband sign · case 02

The adapter reports an incorrect inverse if while other fields remain valid.

Member previewVariant 2 · 3 implementations · 6 checks per implementation

Case contract

A radio receiver provides positive local oscillator L, intermediate frequency I, signed IF channel step d, sideband s equal +1 or -1, second mixer offset m, and source rest frequency R. Sky frequency is L+s*I; image sideband is L-s*I. This is exact mixer bookkeeping only. Output fields are defined by: sky_frequency = d['L']+d['s']*d['I']; sky_increment = d['s']*d['d']; image_frequency = d['L']-d['s']*d['I']; second_conversion = d['L']+d['s']*(d['I']+d['m']); rest_offset = d['L']+d['s']*d['I']-d['R']; inverse_if = d['s']*(d['R']-d['L'])

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	`{"image_frequency": 111, "inverse_if": 20, "rest_offset": -31, "second_conversion": 86, "sky_frequency": 89, "sky_increment": -2}`	`{"image_frequency": 111, "inverse_if": -20, "rest_offset": -31, "second_conversion": 86, "sky_frequency": 89, "sky_increment": -2}`	Failed

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

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