[Spice_discussion] how accurate is conics?

[Joe Knapp]

On Wed, Sep 1, 2010 at 11:00 PM, Trent Waddington
<trent.waddington at gmail.com> wrote:
> and when stepping just 30 days I get a difference in position of
> 24891km using the following code.

Could that be just the difference between the ideal, two-body
Keplerian orbit and the actual one? In the code you give, the
difference grows with time reaching a peak in about 4 years of ~800
million meters, implying the actual Moon is 180 degrees out of phase with
the Keplerian case (the Earth-Moon distance being ~400 million meters).
Then the difference shrinks back to zero around 8.3 years. I guess
that would mean the Moon precesses from the ideal at about 3.5 degrees
per month.

Joe