Re: [find_orb] Re: Update posted to Find_Orb

Bill Gray Mar 14, 2016

Hi Adam,

You've diagnosed the problem exactly: the vectors are equatorial J2000
rather than ecliptic J2000.

The version I've posted has a "workaround" for this (and for the fact
that vectors are always in AU and AU/day; some people really need km and
km/s, and the artsat crowd likes Earth radii and Earth radii/minute).
It currently requires adding a line to 'environ.dat'; instructions
are given at

http://projectpluto.com/findhist.htm#vector_ephems

The paragraph above this gives some discussion of the error you saw,
where you'd get different coordinates from .rwo files than you would
from MPC files. (The former are given with debiasing data "cooked into"
the input; Find_Orb was using that information, even when debiasing
was turned off in the Settings menu.)

Thanks! -- Bill

On 2016-03-05 13:09, limax7@... [find_orb] wrote:
>
>
> Hi
>
> When I generate state vectors ephemeris (center Sun) I have different results in XV YV
> ZV vectors compare to results in elements.txt
>
> Example (elements.txt)
>
> Orbital elements: 2016 EZ26
> Perihelion 2016 Apr 25.991590 +/- 0.0546 TT = 23:47:53 (JD 2457504.491590)
> Epoch 2016 Mar 5.0 TT = JDT 2457452.5 Earth MOID: 0.0016 Ma: 0.0925
> M 346.203985 +/- 0.39 Find_Orb
> n 0.265350889 +/- 0.00728 Peri. 157.223541 +/- 0.36
> a 2.398404060 +/- 0.0439 Node 66.985525 +/- 0.35
> e 0.58865930 +/- 0.00738 Incl. 6.764901 +/- 0.053
> P 3.71 H 22.6 G 0.15 U 9.4
> q 0.986561204 +/- 0.000406 Q 3.810246916 +/- 0.0892
> From 31 observations 2016 Mar. 1-5; mean residual 0".36
> # State vector (heliocentric ecliptic J2000):
> # -1.151924729028 0.275602741425 0.138548677285 AU
> # 2.365142370263 -19.131109078500 -1.145464123342 mAU/day
>
> And ephemeris results:
>
> 2457452.50000 1.000000 1
> 2457452.50000 -1.1519247290 0.1977490727 0.2367444008 0.0023651424
> -0.0170968099 -0.0086608609
>
> Created Sat Mar 05 18:59:05 2016
> Ephemeris start: 5 Mar 2016 0:00:00
> Ephemeris end: 6 Mar 2016 0:00:00
> Times are all TDT
> Positions/velocities are equatorial J2000, in AU and AU/day
>
>
> -----
>
> ups, now I see, in ephemeris is equatorial J2000 and elements.txt is ecliptic J2000
> Can I change ephemeris or settings to output in ecliptic J2000 (to implement in Celestia
> soft).
>
> Adam
>
>