Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Orbit diagram application

  1. Jun 18, 2013 #1

    Jano L.

    User Avatar
    Gold Member

    I would like to have a nice picture/simulation of the Earth - Apophis encounter on April 13th 2029.

    I found this applet

    http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=aPOPHIS;orb=1;cov=0;log=0;cad=0#orb

    but it seems to produce too great error for the time of encounter - the minimal distance much greater than the one currently predicted and the asteroid is depicted to pass the Earth's orbit in front of the Earth, which seems wrong - the semi-major axis of the asteroid is supposed to increase.

    There is also the applet on John Walker's page

    http://www.fourmilab.ch/cgi-bin/Solar/action?sys=-Si

    but I do not know how to get correct orbital elements for it from the available data.

    Does anybody know of a good accessible way to draw accurate orbit diagram for this encounter? Or any similar applet/ application that draws orbits?
     
  2. jcsd
  3. Jun 19, 2013 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

  4. Jun 20, 2013 #3

    Jano L.

    User Avatar
    Gold Member

    Consistent with the latest estimates of closest approach to Earth. This is around 30000 km from the center of the Earth.
     
  5. Jun 20, 2013 #4

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    Did you read the fine print regarding that applet? "This applet is provided as a 3D orbit visualization tool. The applet was implemented using 2-body methods, and hence should not be used for determining accurate long-term trajectories (over several years or decades) or planetary encounter circumstances. For accurate long-term ephemerides, please instead use our Horizons system."
     
  6. Jun 20, 2013 #5

    Jano L.

    User Avatar
    Gold Member

    Yes, I read it. That is why I am asking about some other applet. The Horizons system seems to provide only accurate ephemerides, not orbit diagrams.
     
  7. Jun 20, 2013 #6
    Jano,

    The reason there is an error using the JPL widget is that it is using today's orbit on a day far away into the future. Asteroid orbits are not immutable and vary over time due primarily to planetary encounters and the effects of sunlight. It many cases we also don't know the orbit of an asteroid so well that we can predict where it will be in 100 years with high precision (or maybe even 10 years).

    If you want to use John Walker's diagram, you would need Apophis's orbital elements in 2029. The good news is the MPC Ephemeris service provides orbital elements at future dates. The bad news is we don't provide them in the 8-line format John's program wants, but only in 1-line format. The good news is we're planning to offer 8-line format with the next version of the Ephemeris script. The bad news is I don't know when the release date will be, but most likely before Apophis's flyby in 2029.

    Sorry I can't be of more help!

    —JL Galache
    Minor Planet Center
     
  8. Jun 20, 2013 #7

    Jano L.

    User Avatar
    Gold Member

    Thanks! But contrary to your post, there is the option "MPC 8-line" on the page you gave. However, when I enter

    Ephemeris start date: 2029/04/12 Number of dates to output 2

    I get
    [
    Epoch 2013 Apr. 18.0 TT = JDT 2456400.5 MPC
    M 235.46850 (2000.0) P Q
    n 1.11313176 Peri. 126.45710 +0.87134924 +0.49008396 T = 2456512.37490 JDT
    a 0.9220865 Node 204.22386 -0.46671579 +0.81285109 q = 0.7458161
    e 0.1911648 Incl. 3.33057 -0.15141620 +0.31478694 Earth MOID = 0.00025 AU
    P 0.89 H 19.2 G 0.15 U 0
    From 4050 observations at 2 oppositions, 2004-2013, mean residual 0".34.
    ---
    which seems to be based on the present-day orbit. Is the "MPC 8-line" option limited to present day orbit? It would be great if there was some way to make it work with the orbit in 2029...
     
  9. Jun 20, 2013 #8
    Yes, the 8-line option is there, but it only affects the orbital elements for the current epoch. If you scroll down to the bottom of the results page you should see the 1-line version of the orbital elements at the future date you requested (assuming you filled out the 'Also display elements for epoch' box near the bottom of the Ephemeris request page).
     
  10. Jun 20, 2013 #9

    Jano L.

    User Avatar
    Gold Member

    Ah, yes. Thank you. Can you recommend some text where the significance of all the elements in the 8-line data is explained? Perhaps I can somehow manufacture the 8-line dataset for myself...
     
  11. Jun 20, 2013 #10
  12. Jun 21, 2013 #11

    Jano L.

    User Avatar
    Gold Member

    Thank you.
     
  13. Jul 17, 2013 #12
    Last edited: Jul 17, 2013
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Orbit diagram application
  1. Spacetime Diagrams (Replies: 5)

  2. Things in orbits (Replies: 7)

  3. Gravity and Orbit (Replies: 9)

  4. Calculating orbit (Replies: 9)

Loading...