[Spice_discussion] Re: how accurate is conics?

[Trent Waddington]

On Thu, Sep 2, 2010 at 1:00 PM, Trent Waddington
<trent.waddington at gmail.com> wrote:
> I'm trying to get a feel for how much ephemeris generated by the
> HORIZONS system differs from the mathematical ideal.  I've been
> looking at asteroids but, as a bit of a sanity check, I decided to
> write some code to compare the output of conics with the precalculated
> ephemeris of the Moon.

It occurs to me that this is anything but sane :P

Here's the same code but using heliocentric osculating elements, for
an arbitrary SPK.  I've been using ones generated for asteroids..

    http://quantumg.net/pconics.c
    http://quantumg.net/2006_RH120.bsp

with a step of 1 year the position is 43902km wrong.. that seems like a lot.

Thanks,

Trent