Hi Bill,

Thanks very much for the upgrades. It was cool to see the change in U by "x"ing out astrometry from successive oppositions on a few of my test orbits. I like the one decimal place in U too.

I would like to see the uncertainties in the various elements, by chopping the P and Q values.

Finally, the "now" button is great, but when I tried it for May 1 local time, the first row actually started with May 2. Is Find_Orb accounting for my difference in MDT vs. UT, or it actually applying the first step increment too early? In this case, I would prefer to have the ephemerides start on May 1, whether I increment on a daily or hourly basis from that point onward.

Andrew

--- In find_orb@yahoogroups.com, Bill J Gray <pluto@...> wrote:
>
> Hello all,
>
> The "in-testing" version at
>
> http://home.gwi.net/~pluto/devel/find_orb.htm
>
> now shows the U parameter in the orbital elements.
>
> This is shown _only_ when one does a "full step". (It's not
> particularly meaningful in other contexts). It currently replaces the
> G magnitude parameter, since that is currently always 0.15 anyway.
>
> U is shown to a precision of tenths. That's not because it is really
> that accurate of an indicator; it was mostly to simplify testing. U
> is not shown if the orbit is excessively inaccurate. (To be specific:
> if the formal uncertainty in semimajor axis is greater than the nominal
> semimajor axis, U is probably meaningless and isn't shown.)
>
> U is also not shown for satellites or parabolic/hyperbolic orbits.
>
> If you look in the file 'covar.txt', you'll see quite a bit of
> debugging information from your last "full step". Most of this won't
> be of interest to anybody but me. But the last few lines give sigmas
> for various orbital elements, thus:
>
> sigma_Tp 0.593 days
> sigma_e 0.0175
> sigma_q 0.00358 AU
> sigma_Q 0.206 AU
> sigma_1/a 0.0217 1/AU
> sigma_i 0.131 deg
> sigma_M 0.872 deg
> sigma_omega 0.904 deg
> sigma_Omega 0.435 deg
> sigma_a: 0.103 AU
> sigma_P: 83.7 days
> P = 3.23 years; U=10.2
>
> Similar data is stored in 'monte.txt' when one does a Monte Carlo
> or statistical ranging run. The fact that the covariance uncertainties
> closely match the Monte Carlo uncertainties is very reassuring to me.
>
> (I realize that it would be extremely nice if the above sigmas were
> shown in Find_Orb's on-screen element display. More about this below.
> Also, of course, ephemeris uncertainties are _very_ much to be desired.)
>
> A couple of other small changes:
>
> -- The "Make Ephemeris" dialog now has a "Now" button, to address
> the issue mentioned by Andrew Lowe. There's also a check-box to specify
> that the ephemeris start should be rounded to the nearest step size. (By
> the way, Andrew, I tried the fixed-size font, and it made the elements
> too big to fit. It's possible this can be fixed eventually by rearranging
> the main Find_Orb window.)
>
> -- If the elements are deemed to be truly wacky (heliocentric e=2,
> for example), they are shown in red. (In the console version of Find_Orb,
> they are shown in _blinking_ red. I may try to do that in Windows
> Find_Orb at some point. People new to orbit determination really need
> need something to warn them when elements are bad.)
>
> -- A new Find_Orb user ran into some problems with the Vaisala function.
> To use this, you have to enter the perihelion/aphelion distance in the R1
> field, which is far from obvious. I fixed this: click on "Vaisala", and
> you are prompted to enter the peri/aphelion (apohelion?) distance.
>
>
>
>
> The new uncertainty data raises some questions about on-screen display.
> As far as I know, nobody really makes any use of the P and Q vectors shown
> by Find_Orb. So far, I've slavishly followed the MPC's eight-line format;
> it looks as if it's time to junk that, in favor of something like...
>
> Orbital elements:
> 2002 RG23
> Perihelion 2002 May 15.050409 TT = 1:12:35 +/- 1.18 days
> Epoch 2002 Sep 6.0 TT = JDT 2452523.5 Earth MOID: 0.8646
> M 30.950381 +/- .215
> n 0.271614677 +/- .00041 Peri. 319.339168 +/- .313
> a 2.361387318 +/- .0054 Node 338.982785 +/- .0311
> e 0.20417200 +/- .00038 Incl. 3.186808 +/- .026
> P 3.63 +/- .01 H 18.4 U 8.1 q 1.879258137 Q 2.843516499
> From 19 observations 2002 Aug. 28-Sept. 14; mean residual 0".544.
>
> I'd like to also cram in the sigmas for q and Q, but you get the idea.
> Any thoughts?
>
> -- Bill
>