Diego R Jul 23, 2010
--- In find_orb@yahoogroups.com, Bill J Gray <pluto@...> wrote:
>
> Hi Diego,
>
> My apologies; that message slipped by me!
>
> As you mention, getting positions from two or more observers widely
> separated will help to refine the distance to the object nicely. This
> will happen even if they aren't observing simultaneously. In that
> situation, there's no need to impose a constraint on R1 or R2. Those
> constraints will just fall out, mathematically, from the observations.
>
> To put it another way: suppose two widely separated stations are
> observing an object at roughly the same time. The path shown from one
> station is about 12" away from that shown by the other observing
> station.
>
> In this situation, when Find_Orb tries out various orbits, it
> will find that only those with a narrow range of R1 and R2 produce
> reasonable residual errors. So it may produce "wrong" orbits, but
> any orbit it produces will have roughly the correct value for the
> distance to the object, and there is no need to explicitly constrain
> R1 and/or R2.
>
> This is a very common situation. If an object appears on NEOCP
> and has been observed from two widely separated stations, the
> distance to the object is (usually) nicely defined, unless it's
> very far from us. The only thing that isn't well-defined in
> such a case is the radial velocity; it takes many more observations
> (usually) to figure that one out.
>
> This list _has_ been quiet, perhaps in part because Find_Orb
> hasn't been updated lately, not since the 2010 April 10 version at
>
> http://home.gwi.net/~pluto/devel/find_orb.htm
>
> I do have a version almost ready that adds the ability to compute
> comet non-gravitational parameters (A1 and A2), and has a button for
> the "downhill simplex" method described at
>
> http://www.projectpluto.com/herget.htm#simplex
>
> These features are working, but I've one more I want to get
> completely fixed: statistical ranging. This will allow one to
> compute Monte Carlo type orbits even for very short arcs, and
> even in the case where one has only two observations. Doing this
> hasn't actually been all that tough, but I want a version that
> will be very robust and won't require the user to know too much
> about orbital mechanics. I'm just about there.
>
> -- Bill
>
> Diego R wrote:
> > This group seems to be on holidays!
> >
> > Well, thanks to it, I could see my question was already answered at http://www.projectpluto.com/find_orb.htm#Convergence_problems
> >
> > But I have yet to figure out how to get R1 and R2 from a single distance at a given date.
> >
> > Thanks for any hint!
> >
> > Diego
> >
> > --- In find_orb@yahoogroups.com, "Diego R" <incorregible_98@> wrote:
> >> One of the nice features of Find_Orb is its ability to self impose contrains in one or more of the six orbital parameters. But sometimes, what you got to offer Find_Orb in order to make things easier is distance. Distance to Solar system minor planets can be determined via parallax using two observers in the surface of Earth imaging the object at the same time.
> >>
> >> For instance, two observers 10 000 km apart will get a noticeable 12,50" parallax from an object 1,10 AU away.
> >>
> >> How could that distance be used to help Find_Orb refine its orbit calculations?
> >>
> >> Thanks!
> >>
> >
> >
> >
> >
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