FA-56242 / Astronomical coordinate conventions / Member archive

Occultation shadow coordinate: Egress time confuses chord half-length with diameter · case 02

The adapter reports an incorrect last contact while other fields remain valid.

Member previewVariant 2 · 3 implementations · 6 checks per implementation

Case contract

A reduced occultation shadow travels with signed nonzero velocity v along x. Star coordinate xs is fixed, shadow center starts x0 at epoch t0, and positive half-chord h is supplied. Closest longitudinal crossing is t0+(xs-x0)/v; contacts are ordered using absolute transit duration. Output fields are defined by: crossing_epoch = d['t0']+(d['xs']-d['x0'])/d['v']; shadow_center = d['x0']+d['v']*(d['t']-d['t0']); relative_star = d['xs']-d['x0']-d['v']*(d['t']-d['t0']); first_contact = d['t0']+(d['xs']-d['x0'])/d['v']-abs(d['h']/d['v']); last_contact = d['t0']+(d['xs']-d['x0'])/d['v']+abs(d['h']/d['v']); duration = 2*abs(d['h']/d['v'])

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 1	`{"crossing_epoch": 91.5, "duration": 6.0, "first_contact": 88.5, "last_contact": 88.5, "relative_star": 27, "shadow_center": -6}`	`{"crossing_epoch": 91.5, "duration": 6.0, "first_contact": 88.5, "last_contact": 94.5, "relative_star": 27, "shadow_center": -6}`	Failed

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