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Asteroid May Hit Mars on January 30, 2008 (Read 18439 times)
Tony
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Asteroid May Hit Mars on January 30, 2008
12/23/07 at 21:40:52
 
I'll start a new thread for this asteroid since it a current event that is changing from day to day.  As mentioned in the "asteroids" thread, 2007 WD5 was reported as having a 1 in 75 chance of hitting Mars on January 30, 2008.  This was based on observations through December 21, 2007.  New observations are in.
 
It's predicted path is getting closer to Mars.  The media won't run another story until NASA makes another press release, but the updated numbers from some additional observations are now available.  December 23rd's data shows it is now predicted to pass 17631 km above the Martian surface, more than twice as close as the prediction made with December 21st's data.
 
This doesn't necessarily mean that the odds of 1 in 75 have improved.  I don't know what the error bar is on the new data.  Perhaps as well as the asteroid's trajectory moving closer to Mars, the error bar has shrunk enough to confidently exclude a Martian collision.  Or perhaps not.
 
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frankuitaalst
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #1 - 12/23/07 at 23:14:10
 
In the above picture : is Earth at the right or the left ? (I guess to the left undecided)  
( don't know if the closest approach will be visible from Earth ) . I guess due to the light of Mars the approach won't be visible , even if the approach is on the good side .  
Herunder an animation of the approach as can be seen from Earth ( using the same data ) .  
One can see WD5 approaching to Mars from the right , almost in the plane of the ecliptic . After the closest approach the asteroid is a litle  deviated .  
I can't take out of this frames whether the asteroid passes in front or behind as the pictures refresh.
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2007WD5FromEarth.gif
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #2 - 12/23/07 at 23:46:50
 
In the top image (top down ecliptic view), Earth is on the left.  In the bottom image (within the ecliptic plane), Earth is on the right.  If this seems counter-intuitive, run the above .gsim.  When you're zoomed out enough to see the Earth, the two predictions share the same pixels.
 
Frank, you had mentioned earlier about the error bar for the SMA.  Where do you get that data?  It would be nice to apply it here.
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frankuitaalst
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #3 - 12/23/07 at 23:53:13
 
Ok , makes sense . So it's possible the impact would not be visible from Earth .
 
You can obtain the errors from this site as a sigma-deviation .  
This deviation gets smaller and smaller as new obs come available.  
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2007WD5&orb=1
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #4 - 12/26/07 at 05:39:49
 
I made some simulations of 2007WD5 in Solsyin this is the results ( all simulation are centered in Mars like reference body ):
 
The log of distance of 2007WD5_Mars in close approach:
 

 
MOID variation in 1000 years:
 

 
Eccentricity variation in 1000 years:
 

 
 
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #5 - 12/26/07 at 05:44:58
 
2007WD5 have some ressonance with Mars ?
 

 
 
 
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #6 - 12/26/07 at 06:29:23
 
Tony, a question:
 
I tried and tried but can´t simulate the encounter in Gravity Simulator. In the specific encounter day 2007WD5 and Mars are in opposite points in your orbits !
 
What is wrong ?
 
( I use the 2007WD5 data of NEODyS catalog and the "onlyplanets.gsim" - I retrograde the simulation until  27/10/2007, the epoch for NEODyS catalog, before create the 2007WD5 object with a stepsize os 1s )
 
Thanks !
 
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #7 - 12/26/07 at 10:44:46
 
Quote from APODman on 12/26/07 at 06:29:23:
Tony, a question:

I tried and tried but can´t simulate the encounter in Gravity Simulator. In the specific encounter day 2007WD5 and Mars are in opposite points in your orbits !

What is wrong ?

( I use the 2007WD5 data of NEODyS catalog and the "onlyplanets.gsim" - I retrograde the simulation until  27/10/2007, the epoch for NEODyS catalog, before create the 2007WD5 object with a stepsize os 1s )

Thanks !

[ ]´s

 
"Full System.gsim" is better than "OnlyPlanets.gsim".  OnlyPlanets was designed to give a quick view of the solar system without too much emphasis on accuracy.  With Full System, simply delete the unwanted objects before you use it.  Are you using Gravity Simulator 2.0, or the Beta version?  If 2.0, I'd suggest updating (the link is a sticky at the top of this forum), as I've improved the code in the orbital elements to state vector conversions
 
The "asteroids" thread contains a simulation you can download of 2007 WD5 based on its December 21st solution  
 
If you want to create it yourself, there's 2 ways I would suggest:
Create by State Vectors:
Open FullSystem.gsim
Delete unwanted objects
Propogate the system at 1 second time step to your desired date and pause the simulation.
Use menu Objects > Create Objects to create 2007 WD5.  Just fill in the orbital elements with any dummy data.
Send the following e-mail to horizons@ssd.jpl.nasa.gov and put the word job in the subject line:
Code:
!$$SOF
EMAIL_ADDR=''
START_TIME = '2007-Apr-10 00:00:00'
STOP_TIME = '2007-Apr-10 00:00:01'
TABLE_TYPE = 'Vector'
REF_PLANE = 'Ecliptic'
CENTER = '@010'
COMMAND='2007 WD5'
!$$EOF

 


Change the Start Time to your desired time.  Change Stop Time to 1 second after Start Time.
When you get the return e-mail (usually less than 1 minute) search for the following data.  Highlight and copy the numbers I've boldfaced.  Be careful to not include any leading spaces, and becareful to not exclude any minus sign:
 
$$SOE 2454200.500000000 = A.D. 2007-Apr-10 00:00:00.0000 (CT)  
-5.392879637775785E+07 -3.387908707197315E+08 -3.296068904445007E+06  
1.824188513621929E+01 9.567253283120301E+00 -5.467607677044288E-01

1.144365187923066E+03 3.430720525370878E+08 -1.231012198996011E+01  
$$EOE  
 
Use menu Objects > Edit Objects and paste these 6 numbers into the x-position box.  It will parse them for you into the 6 position and velocity boxes.
 
 
Method 2:  using orbital elements
The link Frank gives in the 4th post in this thread gives you the orbital elements on April 10, 2007.  
Open FullSystem.gsim and delete the unwanted objects.
Propogate the system to April 10, 2007 at 00:00:00
use menu Objects > Create Objects
Enter the orbital elements.  Be sure to zero out all the +- boxes.
 
On your Moid diagram, shouldn't it come closer than 0.009 (about 1.3 million km) in 2008 as it is expected to pass much closer to Mars than this?
 
Thanks for those diagrams.  I'm going to use Gravity Simulator to make an eccentricity graph to compare to yours.  You and Frank will have to teach me how to compute MOID.
 
The resonance you display is a near resonance only.  Near resonances are not uncommon.  This asteroid travels nearly out to Jupiter, so it is likely that if it has a resonance it is with Jupiter, rather than with Mars.  But I've already tried this, and it does not seem to have a resonance with any of the planets.
 
 
 
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #8 - 12/26/07 at 11:04:16
 
Here's the plot of distance to Mars and Earth as I calculated it using the Picard Integrator.  
Zero time was at 01/02/2007 00:00.  
The minimum distance of 0.000146 AU's corresponds well to the distance caluclated by Neodys.  
MARS  0.0001594 .
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2007WD5dist.jpg
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #9 - 12/26/07 at 11:09:41
 
Quote : [/color]Method 2:  using orbital elements  
The link Frank gives in the 4th post in this thread gives you the orbital elements on April 10, 2007.    
Open FullSystem.gsim and delete the unwanted objects.  
Propogate the system to April 10, 2007 at 00:00:00  
use menu Objects > Create Objects  
Enter the orbital elements.  Be sure to zero out all the +- boxes[color=#cc9900].
[/color]End Quote .  
You can go further and click the botton "Ephermeris": then you get into a screen in which you can input the disered values . After some seconds you get the disired data .  
 
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #10 - 12/26/07 at 11:33:33
 
Note : after trying for some time to contact the above horizons site I finally got a return mail .  Smiley.  
I noticed that horizons does not reply to .hotmail adresses .
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #11 - 12/26/07 at 12:59:49
 
Concerning the calculation of the MOID between two elliptical orbits I used the following formulae :  
 
R=a·(1 - e*e)/(1 + e·cos(V))
'XH = R·[cos(O)·cos(V + w - O) - sin(O)·sin(V + w - O)·cos(i)]
'YH = R·[sin(O)·cos(V + w - O) + cos(O)·sin(V + w - O)·cos(i)]
'ZH = R·[sin(V + w - O)·sin(i)].  
 
V beeing the anomaly .
Then calculating the distance = sqrt (......) gives the distance at a given angle V1 and V2.  
Unfortunately there is not a closed formula to derive the MOID , so I help myself with a hill-climbing algorithm in order to get the minimum distance . I can provide the code if needed .  
                                   
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Tony
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #12 - 12/26/07 at 14:23:49
 
Quote from frankuitaalst on 12/26/07 at 11:33:33:
Note : after trying for some time to contact the above horizons site I finally got a return mail .  Smiley.
I noticed that horizons does not reply to .hotmail adresses .  

 
Could it be in your bulk or junk mail box if hotmail thinks it is spam?
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frankuitaalst
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #13 - 12/26/07 at 14:40:19
 
no , I checked , Horizons doesn't seem to reply to hotmail . I get a reply with another address . Funny .
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Re: Asteroid May Hit Mars on January 30, 2008
Reply #14 - 12/28/07 at 10:30:58
 

 
I made a simulation of the Lyapounov time evolution of 2007WD5 in 100 years:
 

 
It's indicate that the orbit evolution of 2007WD5 can be previsible until after 6 years after the encounter. After this time the orbital elements data need to be revised.
 
The fast ascending line is previsible but interesting.
 
News about 2007WD5 in:
 
- http://neo.jpl.nasa.gov/news/news151.html
 
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