Re: Planet MOIDs

cbellh47 Aug 31, 2013

The comet encounter with Mars is at jd: 2456567.227839683
I calculated the distance from the comet to Mars using the position of the comet at that julian date for both the latest MPC orbit for the comet (includes all the observations) and the Find_Orb comet orbit.
There is very little difference between the comet orbits.

I calculated Mars position using DE405 and with lower precision
In all cases, the distance was about 0.0725 to 0.073 AU
much less than MOID for Mars from Find_Orb case.

Thanks for looking.



--- In find_orb@yahoogroups.com, "Matson, Robert D." <matsonr@...> wrote:
>
> Looks like you're missing the oldest astrometry from 9/30/2011
> through 1/28/2012. That might explain the discrepancy.
>
> --Rob
>
> -----Original Message-----
> From: find_orb@yahoogroups.com on behalf of cbellh47
> Sent: Sat 8/31/2013 8:11 AM
> To: find_orb@yahoogroups.com
> Subject: [find_orb] Planet MOIDs
>
> Someone asked me what the planet MOIDs for comet C/2012 S1 (ISON) are. I ran Find_Orb with latest set of MPC observations. Find_Orb gives a good solution but surprisingly it gives an MOID for Mars
>
> all perturbers on
> Ma 0.1487
> all perturbers off
> Ma 0.1519
>
> These values are much larger than Mars close approach nominal distance of about 0.0725 AU.
>
> I'm stuck trying to resolve this.
>
>
> Orbital elements:
>
> C/2012 S1
>
> Perihelion 2013 Nov 28.776713 TT = 18:38:28 (JD 2456625.276713)
>
> Epoch 2013 Nov 4.0 TT = JDT 2456600.5 Earth MOID: 0.0578 Ve: 0.0800
>
> q 0.01244157 (2000.0) P Q
>
> M(N) 6.3 K 10.0 Peri. 345.56518 0.31514246 -0.51236211
>
> Node 295.65268 -0.75893961 0.36934200
>
> e 1.0000019 Incl. 62.40011 -0.56982092 -0.77528803
>
> From 3943 observations 2012 Sept. 21-2013 Aug. 23; mean residual 0".586.
>
> # State vector (heliocentric ecliptic J2000):
>
> # -0.392016068734 0.835201958865 0.015674428334 AU
>
> # 9.434225390851 -23.306814310270 -3.032845430140 mAU/day
>
> # MOIDs: Me 0.1702 Ve 0.0800 Ea 0.0578 Ma 0.1487
>
> # MOIDs: Ju 1.4676 Sa 3.1126 Ur 6.9083 Ne 12.1867
>
> # Elements written: 31 Aug 2013 14:54:56 (JD 2456536.121481)
>
> # Full range of obs: 2011 Sept. 30-2013 Aug. 23 (3960 observations)
>
> # Find_Orb ver: Jul 29 2012 19:28:55
>
> # Perturbers: 007007fe (Merc-Pluto plus Luna)
>
> # Tisserand relative to Earth: 0.14601
>
> # Tisserand relative to Jupiter: 0.06326
>
> # Tisserand relative to Neptune: 0.02193
>
> # %20$Name=C/2012%20S1 $Ty=2013 $Tm=11 $Td=28.776712 $MA=359.99995
>
> # $ecc=1.0000020 $Eqnx=2000.
>
> # $a=-6363.7856344 $Peri=345.56518 $Node=295.65268 $Incl=62.40011
>
> # $EpJD=2456600.500 $q=0.012442 $T=2456625.276713 $H=6.2
>
>
>
> [Non-text portions of this message have been removed]
>