Dangerous Asteroids

[selden]

The Harvard-Smithsonian Center for Astrophysics maintains a list of asteroids which are considered dangerous at http://www.cfa.harvard.edu/iau/lists/Dangerous.html

I quickly translated today's edition of that file into an SSC file for Celestia:
http://www.lepp.cornell.edu/~seb/celest ... 2mar09.zip (87KB)

Expand this zip file into your Extras folder to see the approximate orbits of about 1040 asteroids which fly near the Earth. These are relatively low resolution Keplerian orbits, so they do not accurately predict future encounters.

[ElChristou]

Tx!

[selden]

I discovered a typo in the translation program which caused an error in the parenthetical numbers associated with the proper names of some of the asteroids. It only affected their names, not their orbits.

I've fixed that mistake and updated the SSC file.
Sorry.

[Cham]

Selden,

there should be a way to turn them ON/OFF, since there's already a lot of asteroids in our solar system (and data files available for Celestia). I suggest that you also make a CEL script to identify them.

[selden]

I agree that would be appropriate. This was just a quick 15 minute "throw-away" project as a break from working on other things. Maybe I'll add some selectability in the not too distant future.

[LordFerret]

A question -

When gathering data from JPL/HORIZONS for an asteroid, say a TNO from Harvard's TNO list (http://www.cfa.harvard.edu/iau/lists/TNOs.html), would I want to request the sun body center (heliocentric) or the solar system barycenter based ephemeris?

[selden]

Sun centered would be consistent with the rest of Celestia's SSC files.

[Chuft-Captain]

Selden,

there should be a way to turn them ON/OFF, since there's already a lot of asteroids in our solar system (and data files available for Celestia). I suggest that you also make a CEL script to identify them.

Here's a script to mark them:

mark-Asteroids.zip

[Chuft-Captain]

I've updated the script as I missed a print statement at the end (reporting #asteroids marked). Please download again if you want the latest version.

Sorry 'bout that!

CC

[Cham]

I've found a great solution to the suggestion I made above : add the Visible falsecommand to ALL asteroids in the dangerous.ssc files, so all the potentially dangerous asteroids are invisible by default. Then use the CELX script below to turn OFF all the standard asteroids, while turning ON all the dangerous ones :

Code: Select all

-- Title: R?v?ler 1040 ast?ro?des potentiellement dangereux

function Asteroids()
    SS = celestia:find("Sol")
    SS_bodies = SS:getchildren()
    for k,v in pairs(SS_bodies) do
      if v:getinfo().type == "asteroid" then
         v:setvisible(not v:visible())
      end
   end
end

Asteroids()


Works great !

[Cham]

Selden,

there are HUGE discrepencies for several of the asteroids and some of the standard asteroids in Celestia default package : for example, check out Golevka, Geographos and Toutatis. The orbit is similar to the default one, but the object is lying very far away from its "default" position. What is hapening here ?

[chris]

Selden,

there are HUGE discrepencies for several of the asteroids and some of the standard asteroids in Celestia default package : for example, check out Golevka, Geographos and Toutatis. The orbit is similar to the default one, but the object is lying very far away from its "default" position. What is hapening here ?

I haven't looked at Selden's add-on yet. But remember that the ellipses used for all asteroids in the basic Celestia package are only approximations to the actual orbits. Gravitational perturbations from planets and other bodies will cause the orbit to deviate from a perfect ellipse. Discrepancies are larger after close approaches to planets. I compared the elliptical orbit of Toutatis with an xyzv file generated by HORIZONS--the position of the HORIZONS and Keplerian orbits is in reasonable agreement until the Toutatis' 0.01 AU approach to Earth in September 2004. After that, Toutatis appears to drift away from the position predicted by a purely Keplerian orbit.

--Chris

[Cham]

Chris,

how large is the xyzv file for Toutatis ? This may be very interesting, can you publish it ?

[LordFerret]

This explains the difference I see after I updated Quaoar (experimenting). I have the original Quaoar and Quaoar-ferret, and the ferret version is slightly farther out (distance) and ahead of its counterpart in its orbit. The epoch used in generating the ephemeris (heliocentric) was Jan 01 2009 00:00CT (2454832.5)... if that matters at all - as in: did I do it correctly.

Code: Select all

$$SOE
2454832.500000000 = A.D. 2009-Jan-01 00:00:00.0000 (CT)
 EC= 3.908214224719431E-02 QR= 4.186521590743081E+01 IN= 7.991430925590888E+00
 OM= 1.889420326073197E+02 W = 1.500550940567966E+02 Tp=  2476963.019037579186
 N = 3.427310627030355E-03 MA= 2.841518369208071E+02 TA= 2.797611081767438E+02
 A = 4.356794451227751E+01 AD= 4.527067311712422E+01 PR= 1.050386262513729E+05
2454833.500000000 = A.D. 2009-Jan-02 00:00:00.0000 (CT)
 EC= 3.908328795029563E-02 QR= 4.186493996319933E+01 IN= 7.991440037240962E+00
 OM= 1.889422109101869E+02 W = 1.500634250328265E+02 Tp=  2476965.246554808225
 N = 3.427338383080484E-03 MA= 2.841470155480969E+02 TA= 2.797560814845688E+02
 A = 4.356770929074426E+01 AD= 4.527047861828919E+01 PR= 1.050377756037129E+05
$$EOE