Re: undisplayed (but maybe helpful) data

puck2017 Oct 11 5:42 PM

Hi Bill,

How would I go about decoding the covar.txt file if I all I wanted was the uncertainties in the 7 main orbital parameters?

Thanks,
Andy


--- In find_orb@yahoogroups.com, Bill J Gray <pluto@...> wrote:
>
> Hi Tomas,
>
> As Maik mentions, this data is stored in 'elements.txt'... but not
> actually shown in the Find_Orb dialog, along with Tisserand invariants
> relative to the earth and Neptune. Also stored in that file are the
> state vector, perturbers used in the solution, and MOIDs relative to
> eight planets. (MOIDs are usually only shown if they are small enough
> to be interesting.)
>
> There is also some housekeeping data; for example, it sometimes has
> helped me to know which version of Find_Orb generated a particular set of
> elements, and/or when the elements were generated.
>
> The last two lines are used when generating a pseudo-MPEC, for
> the URLs linking to a SkyMorph search and for the JPL visualization
> tool (the one where you can see the orbit in 3D relative to the
> rest of the solar system).
>
> The only other significant data Find_Orb computes and doesn't show
> is that in 'covar.txt'. This has the covariance and correlation
> matrices, plus the eigenvectors/eigenvalues of the covariance
> matrix. My hope is to use the eigendata in computing variant
> orbits; i.e., if somebody asked for an orbit at +1.3 sigma from
> nominal, the eigenvector data would be used for that purpose,
> giving an orbit along the line of variation. The basic idea
> actually doesn't look all that difficult, though the jargon
> involved was pretty daunting at first.
>
> 'covar.txt' also has the sigmas for the orbital elements. That
> data _is_ highly significant and will eventually be put on-screen.
> Come to think of it, the Jupiter Tisserand data probably should be
> shown if the Jupiter MOID is less than, say, two AU.
>
> -- Bill
>