Re: asteroid (70401) davidbishop - check residuals

Alessandro Feb 2, 2013

Hi Bill,

This is very interesting! Do you think that your finding may also explain why MPC has not rejected those observations even if they are not yet used for the orbit calculation?

I wonder whether this is also why (70401) is now on the critical list...I am not sure if it was there before.

By the way, Bill ... as Alan says, your finding can be interesting for other people if you describe it in the MPML list ...

Best wishes and thanks again,
Alessandro


--- In find_orb@yahoogroups.com, Bill Gray wrote:
>
> Hi Alessandro,
>
> > I just realized that the dT difference depends heavily on weather the asteroid perturbation
> > effect is taken into account or not...
>
> AHA! You are absolutely correct about this. My apologies for misleading you about the
> "timing error".
>
> (70401) Davidbishop passed within about 400000 km of Pallas on 1982 Feb 27. It's really
> rare to see cases where asteroid perturbations matter very much, but they certainly do here.
> If you toss out the five worst observations and include asteroid perturbations, you get
> an RMS error of 0.663". Shut off the perturbations and do a full step, and that bounces
> back up to 1.124, with the 1950 observations having 14.5" residuals in RA.
>
> You could actually use this to get a decent estimate for Pallas' mass. I've occasionally
> thought about revising Find_Orb to do that sort of thing. It would basically just have to
> solve for seven parameters: the usual six orbital elements it normally solves for, plus
> the asteroid mass. Not a big deal, and possibly useful to people doing asteroid mass
> determinations (I don't know what they currently use.)
>
> -- Bill
>