Small object passing by at 0.8 Lunar Distance

[Eelco]

As a curiosity two small NEOs are relatively close to the earth these days, 2007 BD and 2007 BB. Both not much more than 10 meters in diameter, so no big threat even if they would be on impact course, 2007 BD passes at 0.8 LD and 2007 BB at 1.0 LD.

http://neo.jpl.nasa.gov/ca/

has a detailed list of all NEOs coming close, objects within 1.0 lunar distance are luckily rare!

I made a small .ssc file of the current orbital trajectory of 2007 BD, I have not really checked yet whether it??s accurate in Celestia. Time of closest approach should be just about today. I??m assuming all the old SSC parameters still work in the latest Betas, maybe even better now with the sun in its right place! Could be a good check for accuracy whether time and distance are correct.

I calculate a few extra digits for the period from the semimajor axis, because display in Celestia seems sensitive to the accuracy of the orbital period and JPL only gives 4 digits accuracy there, on http://neo.jpl.nasa.gov/cgi-bin/db_shm?sstr=2007 BD.

Maybe of 2007 BB it would be more interesting to check whether it comes close to the moon. But haven??t made a .ssc yet of that one.

Regards, Eelco

The below text can just be pasted as an .ssc textfile in Extras to see the object in Celestia

Code: Select all

# orbital period recalculated from value
# JPL semimajoraxis with formula for two-body problem
# from Sir Isaac Newton ref
# http://en.wikipedia.org/wiki/Semi-major_axis
# http://en.wikipedia.org/wiki/Standard_gravitational_parameter
# using a sidereal year of 365.25636042 mean solar days
# and using 1 AU = 1.49597870691 x 10^11 (?± 3) m

# Asteroid (2007 BD)
# Record: 616752   SPK-ID: 3366282
# Alternate Designation: none

# OSCULATING ORBITAL ELEMENTS
# (heliocentric ecliptic J2000)
# Solution ID = JPL#2
# Epoch = 2007-04-10.0 (2454200.5) TDB



"(2007 BD) " "Sol"
{
   Class "asteroid"
   Mesh "asteroid.cms"
   Texture "asteroid.jpg"
   Radius  0.01 # no data but guess made from H = 26.42
   EllipticalOrbit
   {
      Epoch         2454200.5
      Period            0.62794362417806 # Not all digits will be accurate
      SemiMajorAxis     0.73329717248984   
      Eccentricity      0.344647099120134     
      Inclination       9.27102832632698   
      AscendingNode     297.593323014539     
      ArgOfPericenter   359.149482100349     
      MeanAnomaly       309.96343125202   
   }
Albedo         0.7   # fiction, large because we want it visible!!!
RotationPeriod    8 # (hours) random choice
}


[selden]

I think the European site NeoDys tends to publish more reliable orbital parameters for some reason. They indicate that the parameters for 2007BD are only good to about 2 parts in 10^-5.

[LordFerret]

Should be fun to take a look! Thanks for posting!

When I first saw this post I was hoping it had something to do with 3753 Cruithne and 2002 AA29, as I understand they're considered Earth "companions" {as per http://www.nineplanets.org/earth.html }. But I cannot find them in Celestia, unless I've got the names incorrect. Anyone familiar with them?

[Hungry4info]

http://en.wikipedia.org/wiki/3753_Cruithne
http://en.wikipedia.org/wiki/2002_AA29

[Eelco]

Hello all,

This is an old thread I know, but what I wanted to post is a very similar subject to this old post of mine: another upcoming, very close pass of a small NEO body, I called it the Valentine's Day asteroid. NASA has made a nice simulation video of it but with Celestia we can do much the same with just a simple text file in the "Extras" folder. My data are just from the simple JPL Small-Body Database browser page on the asteroid 2012 DA 14. When fed into Celestia it can't model the minimum distance or close approach time as accurate as NASA can do, but it can give you an idea especially the view from the asteroid as it approaches earth is still fascinating, this asteroid is coming almost directly from below, from the celestial south pole, heading for Antarctica and with Polaris directly in the center of the image, only at the last moment the asteroid veers away, somewhere with the ocean south of India below where it is still night, and only then it will become visible to telescopes in the Northern hemisphere for more measurements of the orbit or asteroid characteristics. I updated the file with the latest JPL browser data from today, latest observation used for the elliptical orbit estimates is from yesterday, feb. 10. There are radar observations planned from the big dish at Goldstone, California and they had a nice write up about the object; http://echo.jpl.nasa.gov/asteroids/2012 ... nning.html
I copied their estimates of rotation period and albedo for the .ssc file on 2012 DA 14 (Not all those digits behind the fraction mark are significant, I did not round them at all. I assumed a year of 365.24 days)

Code: Select all

# (2012 DA14)
# Alternate Designation: none
# Classification: Apollo [NEO]

# OSCULATING ORBITAL ELEMENTS JPL data, modified
# (heliocentric ecliptic J2000)
# Reference JPL 43
# Epoch = 2013-04-18.0 (2456400.5) TDB


" (2012 DA14) " "Sol"
{
   Class "asteroid"
   Mesh "asteroid.cms"
   Texture "asteroid.jpg"
    Radius  0.025 # H = 24.109, diam. ~50 meters (+- a factor of two)
   EllipticalOrbit
   {
      Epoch       2456400.5
      Period            0.86860296412465967582959150147848
      SemiMajorAxis      .9103340965670457
      Eccentricity       .08938693852024779 
      Inclination      11.60819544854722
      AscendingNode   146.9957742062764 
      ArgOfPericenter 195.535092451876 
      MeanAnomaly     231.0965754903669 
   }
   Albedo            0.2    # estimate Nick Moskovitz
   RotationPeriod    0.25   # ~6 h, N. Moskovitz (0<RP<365)
}


[Chuft-Captain]

That JPL page has been updated with new elements.

Updated version for the new solution date of 2013-Feb-12 01:50:19:

Code: Select all

# (2012 DA14)
# Alternate Designation: none
# Classification: Apollo [NEO]

# OSCULATING ORBITAL ELEMENTS JPL data, modified
# (heliocentric ecliptic J2000)
# Reference JPL 43
# Epoch = 2013-04-18.0 (2456400.5) TDB
# solution date         2013-Feb-12 01:50:19

"2012 DA14 (CC)" "Sol"
{
   Class "asteroid"
   Mesh "asteroid.cms"
   Texture "asteroid.jpg"
    Radius  0.025 # H = 24.109, diam. ~50 meters (+- a factor of two)
   EllipticalOrbit
   {
      Epoch       2456400.5
      Period            0.86857636717356960985626283367556
      SemiMajorAxis     0.9103321290555076
      Eccentricity      0.08938909858320071
      Inclination      11.60818892907225
      AscendingNode   146.9957742338762
      ArgOfPericenter 195.5345028962937
      MeanAnomaly     231.0974228748705
   }
   Albedo            0.2    # estimate Nick Moskovitz
   RotationPeriod    0.25   # ~6 h, N. Moskovitz (0<RP<365)
}

According to JPL the time of closest approach is 2013-Feb-15 19:25 UTC (2456339.309598331 JD), however this version in my Celestia (using SPICE kernels) makes it's closest approach about 2.5 hours earlier than the predicted time.

Your older version arrives about 3 hours after the predicted time.

Quite a big difference between the two versions.
(I've given this one a different name, so you have both installed at the same time to compare if you so wish.)

CC

[Eelco]

Hello Chuft-Captain,

Thanks for the update! The new orbit, after the close passage, is maybe still uncertain, because it depends on the precise conditions under which the passage occurred. To determine the new orbit better, the astronomers need more observations and for that you first have to be able to find the object in a telescope. So that is why I'm guessing there are frequent updates at the moment. The close passage has changed the orbit so much that it is no longer an asteroid of the Apollo class but it has moved to the Aten class. Fascinating, is that what happened to more of the Aten class asteroids I wonder? I have not looked it up. All of these different sets of orbital elements can only describe the orbit rather inaccurately, because it is not really an ellips at the moment. The period has shortened enormously for instance, my original version was from JPL 35 and had a period of ? 1.0028 year so that described a very different elliptical orbit. But the moment of close approach will be the time with the greatest gravitational perturbations, so an elliptical orbit centered on that time will also not have much practical value for the time before or after the moment of close approach... I think it only makes a tangent to the real orbit in this point of the closest passage to earth.

Regards, Eelco

[John Van Vliet]

--- edit ---

[John Van Vliet]

--- edit----

[Chuft-Captain]

John,

Your Timeline version of the asteroid seems wrong. - Never gets closer than about 109,000 km to Earth.

I suspect you've generated the elements relative to the SSB at Horizons, however you've specified an OrbitFrame relative to "Sol" in the SSC.
(or somehow got the wrong elements in the SSC).
The orbit-frame specified in the SSC needs to be consistent with the Center object chosen to generate the elements.

I suggest you re-generate them at HORIZONS but specify Sol as the Center.

CC

FWIW, here's the latest elements as I found them (Sol centered):

Code: Select all

# solution date         2013-Feb-14 13:04:22

"2012 DA14 (2013-Feb-14_13:04:22)" "Sol"
{
   Class "asteroid"
   Mesh "asteroid.cms"
   Texture "asteroid.jpg"
    Radius  0.025 # H = 24.109, diam. ~50 meters (+- a factor of two)
   EllipticalOrbit
   {
      Epoch       2456400.5
      Eccentricity      0.08939725461638723 # e
      SemiMajorAxis     0.9103253745245672   # a
      Inclination         11.60817262655783    # i
      AscendingNode      146.995823771085   # node
      ArgOfPericenter    195.533863834364    # peri
      MeanAnomaly        231.0986125038471   # M
      Period            0.868566700127538   # period = 317.2439872215834 / 365.25
   }
   Albedo            0.2    # estimate Nick Moskovitz
   RotationPeriod    0.25   # ~6 h, N. Moskovitz (0<RP<365)
}

[John Van Vliet]

--- edit----

[Limax7]

Hi here is bsp add-on with asteroid 2012 DA14 from 1900-01-01 to 2100-01-01 generated in telnet HORIZONS

RAR - 2.1 MB (extract to extras or extras-standard folder)
http://ge.tt/api/1/files/6rVvEyY/0/blob?download