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Fix double km-to-AU conversion in geo_to_ssbary #21

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Merged
ijiraq merged 1 commit into from
Oct 6, 2026
Merged

Fix double km-to-AU conversion in geo_to_ssbary #21

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7 changes: 4 additions & 3 deletions orbfit/ephem_earth.c
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Original file line number Diff line number Diff line change
Expand Up @@ -803,14 +803,15 @@ void geo_to_ssbary(double jd, double *x, double *y, double *z)
geocenter_ssbary(jd, xgeo);
/* fprintf(stderr, "XGEO: %lf %lf %lf\n", xgeo[0], xgeo[1], xgeo[2]);
fprintf(stderr, "OBS: %lf %lf %lf (km)\n", *x, *y, *z); */
/* R1.AU is in km */
*x /= R1.AU;
*y /= R1.AU;
*z /= R1.AU;
/* fprintf(stderr, "OBS: %lf %lf %lf (au)\n", *x, *y, *z); */
/* Add in to give observatory coords in ICRS */
*x = xgeo[0] + *x/R1.AU;
*y = xgeo[1] + *y/R1.AU;
*z = xgeo[2] + *z/R1.AU;
*x += xgeo[0];
*y += xgeo[1];
*z += xgeo[2];
/* fprintf(stderr, "PRO: %lf %lf %lf\n", *x, *y, *z); */
return ;
}
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21 changes: 19 additions & 2 deletions test/test_orbit.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,9 @@ def test_parser(self):
def test_fitradec(self):
orbit = mp_ephem.BKOrbit(None, self.mpc_filename)
orbit.predict(orbit.observations[0].date)
self.assertAlmostEqual(orbit.a.to('au').value, 17.08, 0)
self.assertAlmostEqual(orbit.a.to('au').value, 91.82, 0)
# JPL SBDB gives i=3.32 deg for 2020 KQ11
self.assertAlmostEqual(orbit.inc.to('degree').value, 3.3, delta=0.5)

class SimonFormat(unittest.TestCase):

Expand All @@ -36,7 +38,7 @@ def test_parser(self):
def test_fitradec(self):
orbit = mp_ephem.BKOrbit(None, self.mpc_filename)
orbit.predict(orbit.observations[0].date)
self.assertAlmostEqual(orbit.a.to('au').value, 43.8015219, 3)
self.assertAlmostEqual(orbit.a.to('au').value, 43.68817, 3)


class OrbitFit(unittest.TestCase):
Expand Down Expand Up @@ -152,6 +154,21 @@ def test_alphanumeric_obscode(self):
self.assertAlmostEqual(orbit.a.to(units.AU).value, self.orbit.a.to(units.AU).value, 3)
self.assertAlmostEqual(orbit.e.value, self.orbit.e.value, 4)

def test_geocentric_location_matches_obscode(self):
"""
Supplying the geocentric position (km) of Mauna Kea must give the same orbit as obscode 568.
"""
mko = coordinates.EarthLocation.from_geodetic(-(155 + 28/60. + 19.9/3600.) * units.degree,
(19 + 49/60. + 33.9/3600.) * units.degree,
4207.24 * units.m)
observations = [obs for obs in self.observations if not obs.null_observation]
for obs in observations:
position, _ = mko.get_gcrs_posvel(obs.date)
obs.location = ObserverLocation(*position.xyz.to(units.km).value)
orbit = mp_ephem.BKOrbit(observations)
self.assertAlmostEqual(orbit.a.to(units.AU).value, self.orbit.a.to(units.AU).value, 3)
self.assertAlmostEqual(orbit.e.value, self.orbit.e.value, 4)

def test_predict_space_observatory(self):
"""
A space observatory without a supplied position is predicted from the geocenter.
Expand Down
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