FA-55867 / Astronomical coordinate conventions / Member archive
Astrometric perspective transport: Physical tangential displacement is emitted in angular-rate units · case 02
The adapter reports an incorrect tangential displacement while other fields remain valid.
Case contract
A finite one-axis astrometric model has initial distance r>0, radial speed v, tangential speed u, elapsed t, and tangent origin x. New distance R=r+v*t remains positive for all fixtures. Direction tangent is x+u*t/R, and apparent angular rate is u*r/R**2; this is a rectilinear perspective model. Output fields are defined by: radial_distance = d['r']+d['v']*d['t']; tangential_displacement = d['u']*d['t']; direction_tangent = d['x']+d['u']*d['t']/(d['r']+d['v']*d['t']); angular_rate = d['u']*d['r']/(d['r']+d['v']*d['t'])**2; radial_fraction = d['v']*d['t']/d['r']; initial_angular_acceleration = -2*d['u']*d['v']/d['r']**2
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 fixtureThis sample comes from the broken implementation of a controlled reproducer.
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| astronomical fixture 0 | {"angular_rate": 0.1008, "direction_tangent": 5.24, "initial_angular_acceleration": -0.027210884353741496, "radial_distance": 25, "radial_fraction": 0.19047619047619047, "tangential_displacement": 0.2857142857142857} | {"angular_rate": 0.1008, "direction_tangent": 5.24, "initial_angular_acceleration": -0.027210884353741496, "radial_distance": 25, "radial_fraction": 0.19047619047619047, "tangential_displacement": 6} | Failed |
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