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C/2002 T7 orbit

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  • terryjlovejoy
    2002T7 orbit Its perhaps a little early to be sure, but running 103 C/2002T7 observations listed on MPEC through Findorb suggests a distinct elliptical orbit.
    Message 1 of 7 , Nov 1, 2002
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      2002T7 orbit

      Its perhaps a little early to be sure, but running 103 C/2002T7
      observations listed on MPEC through Findorb suggests a distinct
      elliptical orbit. i.e

      C/2002T7
      Perihelion 2004 Apr 29.523416 TT
      Epoch 2002 Oct 13.0 TT = JDT 2452560.5
      M 359.01944 (2000.0) P Q
      n 0.00173696 Peri. 158.99240 0.41259690 -0.84696387
      a 68.5396750 Node 94.67728 -0.87636149 -0.26866551
      e 0.9913210 Incl. 160.34198 -0.24850417 -0.45877121
      P 567.43 H 8.7 G 0.15 q 0.5948524
      From 103 observations 2002 Oct. 12-31; RMS error 0.627 arcseconds

      It would be interesting to get the opinion from others with more
      experience with orbital computations.

      Regards,
      Terry
    • sfhoenig@aol.com
      Hello Terry, my experience especially with 2002 O4 is that not the amount of observations are the main problem but a short arc. This experience came from the
      Message 2 of 7 , Nov 1, 2002
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        Hello Terry,

        my experience especially with 2002 O4 is that not the amount of observations
        are the main problem but a short arc. This experience came from the try to
        determine e within the first month where Maik and me suggested a medium
        periodic solution. However my first reliable excentricity (e~1.0008) could be
        determined with a 4 weeks arc. After that first negative experience with this
        topic I started to test it with other long periodic comets to compare
        short-arc-solution to one-month-solution and personally I decided to not
        predict e before a reasonable arc is observed.

        Additionally to Terry's question I would like to ask the community what
        software do you use for orbit determination? Is there something recommendable
        beyond FindOrb and Solex (which actually uses FindOrb)?

        Regards, Sebastian
        ---------------------------------------------
        Sebastian F. Hönig
        Jahnstr. 38
        69221 Dossenheim
        Germany
        Phone: ++49-(0)6221-862059
        ++49-(0)162-9179431
        eMail: Sebastian@..., sfhoenig@...
        homepage: www.sungrazer.org


        [Non-text portions of this message have been removed]
      • reinder j bouma
        ... Hi Terry, and others, Also using FIND_ORB I found a very similar solution (not surprising): C/2002 T7 (LINEAR) Perihelion 2004 Apr 29.107299 TT Epoch 2002
        Message 3 of 7 , Nov 1, 2002
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          terryjlovejoy wrote:
          >
          > 2002T7 orbit
          >
          > Its perhaps a little early to be sure, but running 103 C/2002T7
          > observations listed on MPEC through Findorb suggests a distinct
          > elliptical orbit. i.e
          >
          > C/2002T7
          > Perihelion 2004 Apr 29.523416 TT
          > Epoch 2002 Oct 13.0 TT = JDT 2452560.5
          > M 359.01944 (2000.0) P Q
          > n 0.00173696 Peri. 158.99240 0.41259690 -0.84696387
          > a 68.5396750 Node 94.67728 -0.87636149 -0.26866551
          > e 0.9913210 Incl. 160.34198 -0.24850417 -0.45877121
          > P 567.43 H 8.7 G 0.15 q 0.5948524
          > >From 103 observations 2002 Oct. 12-31; RMS error 0.627 arcseconds
          >
          > It would be interesting to get the opinion from others with more
          > experience with orbital computations.
          >
          > Regards,
          > Terry

          Hi Terry, and others,

          Also using FIND_ORB I found a very similar solution (not surprising):

          C/2002 T7 (LINEAR)
          Perihelion 2004 Apr 29.107299 TT
          Epoch 2002 Nov 22.0 TT = JDT 2452600.5
          M 359.17107 (2000.0) P Q
          n 0.00158158 Peri. 158.92599 0.41380291 -0.84648705
          a 72.9581430 Node 94.68928 -0.87592762 -0.26995375
          e 0.9918333 Incl. 160.35886 -0.24802810 -0.45889501
          P 623.18 H 8.7 G 0.15 q 0.5958204
          >From 104 observations 2002 Oct. 12-31; RMS error 0.624 arcseconds

          Although the arc is still rather short, I feel that this result is not
          too far off.
          In this case the astrometry is of good quality, and therefore, I feel
          that Sebastian's comparison with the calculations of C/2002 O4 is not
          quite appropriate where the astrometry was VERY poor in many cases,
          which made selection of the good astrometry rather tricky, particularly
          over the first 3-4 weeks...
          I noted though, that e tends to increase slightly with increasing arc in
          the case of 2002 T7, so we should wait a few weeks longer, before we
          start celebrations...
          If this turns out to be a comet with a relatively short period, then
          southern observers may be in for a real fine treat in April/May 2004..

          By the way, FIND_ORB users should note that older versions of this
          program have a serious error in the calculation of the residuals, which
          may seriously affect the selection of good astrometry. When comparing
          this program's residuals with the ones published in the MPEC's I noted
          that they got far too large for comets at high declinations, suggesting
          that cos(Dec) was not taken into account properly. Bill Gray quickly
          confirmed my suspicion (and found one or two other bugs) and now has the
          correct version at his homepage. If you use a version downloaded before
          about 10 September, than you should replace it asap!

          Best regards,
          Reinder

          -------------------------------------------------------------------
          Reinder J. Bouma e-mail (1): rjbouma@... or rjbouma@...
          Bekemaheerd 77 e-mail (2): comets.nl@...
          9737PR Groningen homepage: http://www.shopplaza.nl/astro/
          The Netherlands phone: +31 (0)50-5418227
          -------------------------------------------------------------------
        • David Seargent
          ... From: terryjlovejoy To: Sent: Friday, November 01, 2002 10:25 PM Subject: [comets-ml] C/2002 T7 orbit
          Message 4 of 7 , Nov 2, 2002
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            ----- Original Message -----
            From: terryjlovejoy <terryjlovejoy@...>
            To: <comets-ml@yahoogroups.com>
            Sent: Friday, November 01, 2002 10:25 PM
            Subject: [comets-ml] C/2002 T7 orbit


            > 2002T7 orbit
            >
            > Its perhaps a little early to be sure, but running 103 C/2002T7
            > observations listed on MPEC through Findorb suggests a distinct
            > elliptical orbit.

            When I first read the description of this comet, I wondered whether it might
            not be dynamically new. There seems to be little coma and no tail and the
            descriptions seem like those of a comet in a low-activity state. First-time
            Oort Cloud comets as bright as T7 are usually more active at 6AU and already
            show distinctive ice particle tails (cf. 2001 Q4 in recent months). It will
            be interesting to see if the orbit confirms this suspicion. If it does
            happen to be an old comet, it may 'turn on' at about 3 AU and become
            intrinsically even brighter than it appears to be at present. These are
            still very early days however, and it may yet turn out that the comet is a
            new one after all (like 2001 Q4 and 2002 O4, for which elliptical solutions
            seemed possible on early results).

            David
          • Hirohisa Sato
            Dear all, I calculated the following parabolic orbits. There is the possibility of hyperbolic orbits. For the moment, it does not become elliptic orbits.
            Message 5 of 7 , Nov 4, 2002
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              Dear all,

              I calculated the following parabolic orbits.
              There is the possibility of hyperbolic orbits.
              For the moment, it does not become elliptic orbits.

              Orbital elements:
              C/2002 T7 (LINEAR)
              T 2004 Apr. 23.25717 TT Sato
              q 0.6135555 (2000.0) P Q
              Peri. 157.80821 +0.43335008 -0.83817078
              Node 94.85680 -0.86873336 -0.29071677
              e 1.0 Incl. 160.58736 -0.23981254 -0.46146885
              From 117 observations 2002 Oct. 12-Nov. 3, mean residual 0".48.

              Residuals in seconds of arc as follows.
              http://www.hi-ho.ne.jp/hirohisa-sato/Index/c2002_t7orb.txt

              Best Regards,
              --
              Hirohisa Sato
              Sukagawa, Fukushima, Japan
              e-mail : hirohisa-sato@...
            • Maik Meyer
              Hi all, concerning the question if the orbital elements of this comet will become elliptical or hyperbolical (or indeterminate in this regard) I have to add
              Message 6 of 7 , Nov 4, 2002
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                Hi all,

                concerning the question if the orbital elements of this comet will
                become elliptical or hyperbolical (or indeterminate in this regard) I
                have to add that my experience (I am NO expert on this!) is really that
                a reasonable long arc is neccessary before any statements can be made.

                As Sebastian already pointed out, my first solutions for his (C/2002 Q4)
                comet were clearly elliptical. Even the residuals for the elliptical
                solution were lower compared to the parabolic ones. As it turned out,
                this comet now has a hyperbolical orbit. Not without good reason Brian
                Marsden waits a considerable long time before changing a parabolic
                solution to a hyperbolic or elliptical orbit in the MPECs/MPCs.

                But nevertheless it will be most interesting to monitor the astrometry
                and evolution of the orbital solutions of this comet. Maybe this comet
                is not dynamically new (as apparently is the case with C/2002 Q4) and at
                least one of the two expected naked-eye comets will be an extraordinary
                object.

                Kind regards, Maik
                --
                If they give you ruled paper, write the other way. * Juan Ramon Jimenez
                ________________________________________________________________________
                maik@... http://www.comethunter.de
                German Comet Section http://www.fg-kometen.de
                http://groups.yahoo.com/group/comets-ml
              • Maik Meyer
                Maik Meyer wrote much more wrongly: [deleted for your convenience] I do not know what I was thinking when I corrected my correct posting. I think I need some
                Message 7 of 7 , Nov 4, 2002
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                  Maik Meyer wrote much more wrongly:

                  [deleted for your convenience]

                  I do not know what I was thinking when I corrected my correct posting. I
                  think I need some vacation under clear and dark sky.

                  Maik
                  --
                  If they give you ruled paper, write the other way. * Juan Ramon Jimenez
                  ________________________________________________________________________
                  maik@... http://www.comethunter.de
                  German Comet Section http://www.fg-kometen.de
                  http://groups.yahoo.com/group/comets-ml
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