FA-55350 / Astronomical coordinate conventions / Member archive
Ephemeris relative state: Retarded barycentric target position is propagated with relative rather than target velocity · case 05
The adapter reports an incorrect retarded target position while other fields remain valid.
Case contract
A supplied ephemeris state for target T and center C is barycentric. Observer topocenter adds station displacement s and station velocity v to C. Output relative vectors use this explicit one-dimensional reduction; light-time iteration and relativity are outside scope. Output fields are defined by: geocentric_position = d['tx']-d['cx']; geocentric_velocity = d['tv']-d['cv']; observer_position = d['cx']+d['s']; observer_velocity = d['cv']+d['v']; topocentric_position = d['tx']-d['cx']-d['s']; retarded_target_position = d['tx']-d['tv']*d['dt']
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 | {"geocentric_position": 74, "geocentric_velocity": 9, "observer_position": 32, "observer_velocity": 4, "retarded_target_position": 152, "topocentric_position": 72} | {"geocentric_position": 74, "geocentric_velocity": 9, "observer_position": 32, "observer_velocity": 4, "retarded_target_position": 56, "topocentric_position": 72} | Failed |
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