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Osculating Elements for Near-Earth Asteroids

Tom Polakis

April 02, 2017 06:32

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I have been using SkySafari 5 Pro to locate asteroids on which I'm doing photometric imaging.  The coordinates for a specific time typically match those in JPL Horizons or the MPC service very closely for Main Belt asteroids.  I'm having trouble with a fairly nearby object, however, in which the position is in error by nearly 5', as verified by astrometry of my images.  The asteroid is (143404) BD44, which is currently at a distance of about 0.15 a.u.

Orbital elements were automatically updated earlier today.  I'm pretty sure that SkySafari is correctly using topocentric, and not geocentric, coordinates.  I'm told by a colleague that the error may be due to it not using osculating elements. Can near-earth positions be corrected to better accuracy than what I'm presently seeing?  Thanks.

 

Tom

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  Bill Tschumy April 18, 2017 23:21

  Tom,

  Sorry, I just saw this posting.  Yes, the predictions are topocentric.  Your friend is presumably talking about the perturbed orbit.  This is a computationally difficult computation.  We actually do have code in place to start integrating the orbit of a body if it has high eccentricity and comes close to the Sun or Earth (I think we are the only planetarium program to do this).  I would have to look specifically at the asteroid you refer to to see if it meet the conditions for integrating a perturbed orbit.

  When I search for the asteroid 143404, I find two entries.  One has BD44 appended to the name and the other doesn't (but they are the same object apparently).  I'm not sure which is the correct object or why the Minor Planet Center lists both.  Perhaps the other is closer to where you expect the object to be.