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I'm looking for a NAIF SPK file (these typically end in .bsp) for a bunch of asteroids in the J2000 reference frame. I found ast343de430.bsp at ftp://ssd.jpl.nasa.gov/pub/eph/small_bodies/asteroids_de430/ast343de430.bsp. They seem to be referenced to J2000 and they they have 10 (sun) as their center reference, but when I go to plot them they look wonky.

When I overlay their traces on de430.bsp I get epicyclic looking traces for each individual body and the cloud of points seem to form the characteristic asteroid belt shape but offset by 2-3AU.

I'm using a basic SPK reader I've developed myself. The code is here (MIT licensed, as the question arose below). This reader is fine with the publicly released large body and satellite files (https://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/planets/, https://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/satellites/)

Has anyone used this file and did they have any issues with it? Thanks!

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The ast343de430.bsp file looks to be fine. There is only one thing of note - all bodies in this file are referenced to the sun (10) but the ephemeris of the sun is not included. (The reason is given here - the author of this file considers the position of the Sun to be better defined than the SSB). For this reason an additional .bsp file which contains the SSB should be used, unless you are happy using the Sun as origin of the co-ordinate system.

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    $\begingroup$ I think you can definitely accept this one though ;-) $\endgroup$
    – uhoh
    Commented Oct 21, 2018 at 11:48

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