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PostPosted: Sat, 29-02-20, 14:31 GMT 
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I recently wrote a script to create a ssc from IAU Minor Planet Electronic Circulars(MPEC) for 2016 HO3 (469219 Kamo'oalewa). I also have a semi-automated method for the JPL Small-Body Database Browser information.

When I viewed them in Celestia, the MPEC ssc and JPL ssc placed the asteroids roughly 25 million km apart.

Is there really that much discrepancy between JPL and MPC?

Being self-taught I am afraid I may have neglected some crucial parameter.

Code:
"2016 HO3 JPL" "Sol"
{   Class    "asteroid"
   Texture "asteroid.*"
   Mesh "asteroid.cms"
   Radius 0000.0205
   OrbitFrame { EclipticJ2000 { Center "Sol" }}
   EllipticalOrbit
   {   Epoch 2459000.5 #(2020-May-31.0)
      Period 1.0017
      SemiMajorAxis 1.001247952341482
      Eccentricity .1033008457332786
      Inclination 7.785290872333171
      AscendingNode 66.15571209330616
      ArgOfPericenter 306.1878387017647
      MeanAnomaly 236.2931089110786
   }
   Albedo 0000.2002 #calculated from Absolute magnitude of 24.3
}


Code:
# derived from MPEC/MPEC2016-H63
"2016 HO3 MPEC" "Sol"
{   Class "asteroid"
   Texture "asteroid.*"
   Mesh "asteroid.cms"
   Radius 0.028 #Calculated from Absolute magnitude of 23.9 and geometric albedo of 0.15
   OrbitFrame { EclipticJ2000 { Center "Sol" }}
   EllipticalOrbit
   {   Epoch 2457600.5
      Period 1.0100
      SemiMajorAxis 1.0034412
      Eccentricity 0.0997006
      Inclination 7.61685
      AscendingNode 66.40301
      ArgOfPericenter 306.12700
      MeanAnomaly 298.58530
   }

   Albedo 0.15 #calculated from Absolute magnitude of 23.9
}

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PostPosted: Sun, 01-03-20, 5:17 GMT 
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you do have a possible typo in the first one
Quote:
Eccentricity .1033008457332786

missing 0 in front of that decimal point

also you can drop down to using only 6 significant figures
Code:
Eccentricity  0.10330


as i recall celestia only uses 6 or 8 decimal places.

the only reason i use more in the SPICE orbits is it is the easiest method ( copy/past)

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PostPosted: Sun, 01-03-20, 14:37 GMT 
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@JVV Thanks for taking the time to reply. You have helped me in the past and I have the utmost respect for your work.

The Eccentricity isn't a typo, my tests show it works the same with or without the leading zero. I added the zero just to be sure.

I installed your Spice Kernel ssc for 2016 HO3. This ssc puts the asteroid closer to my JPL ssc. This is not surprising since JPL publishes the data.

I also created another ssc based on the Lowell Observatory AstorbDB https://asteroid.lowell.edu/astinfo/. See Code below.
This also puts the asteroid closer to my JPL ssc (with or without the "extra digits"). The MPC ssc is still 25 million km away.

So... None of my investigation explains why the MPC data has a discrepancy.
I would like to continue to use MPC because it has (sometimes) a value for geometric albedo which I use to calculate the radius.

Any thoughts? Anyone?

Code:
# derived from Astorb
"2016 HO3 Astorb" "Sol"
{    Class "asteroid"
     Texture "asteroid.*"
     Mesh "asteroid.cms"
     Radius 0.02
     OrbitFrame { EclipticJ2000 { Center "Sol" }}
     EllipticalOrbit
     {    Epoch 2458900.5 #2020-Feb-21
          Period 1.00133
          SemiMajorAxis 1.001
          Eccentricity 0.103
          Inclination 7.782
          AscendingNode 66.19
          ArgOfPericenter 306.274
          MeanAnomaly 137.764
     }

    Albedo 0.2306  #calculated from Absolute magnitude of 24.2
}

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PostPosted: Sun, 01-03-20, 15:47 GMT 
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Location: N 42.38846 W 83.45456
i am assuming you have looked into the different Epochs
"Epoch 2459000.5" and "Epoch 2457600.5"

after 1400 days errors can add up in the way that celestia calculates the orbit .
However it should not be as big as 25 mill. Km. for only 4 to 5 orbits

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