Celestia Forums

Posted: **15.04.2011, 21:54**

Hi, I am checking asteroid Apophis orbit and see when it is close, my Celestia is 2 years to fast so close to Earth is 2 years behind. I even checked it is close in 2031, it should stand 2029.

Posted: **16.04.2011, 09:38**

Can you post your .SSC for 2004 MN4?

Posted: **16.04.2011, 13:41**

Remember that Celestia does not do any gravitational corrections. It's only a display program.

Simple Keplerian orbits (the kind defined by EllipticalOrbit declarations) are valid only at one specific date. They're called "osculating orbits" because they touch (kiss) an orbiting object's real trajectory at only one point. Gravitational effects cause objects to drift away from their idealized Keplerian orbits more or less quickly. Low-mass objects like asteroids drift away more quickly than planets do.

To get a better Keplerian approximation, you can request orbital parameters from JPL's Horizons ephemeris server for the predicted date of the encounter.

To show a better continuous path, though, you should use xyz or xyzv trajectories obtained from Horizons. To show an accurate flyby, you must use Spice kernels for both the asteroid and the Earth.

Posted: **16.04.2011, 14:38**

CAP-Team wrote:Can you post your .SSC for 2004 MN4?

you find it on celestiamotherlode.net
go on asteroids and you will find it

Posted: **16.04.2011, 21:10**

Here are some orbital elements as provided by Horizons for some dates of interest.
For a description of the difficulty of predicting the future path of Apophis, please see
http://neo.jpl.nasa.gov/apophis/

Code: Select all

#2455666.500000000 = A.D. 2011-Apr-15 00:00:00.0000 (CT)
# EC= 1.911121116338028E-01 QR= 7.460229571723584E-01 IN= 3.331912907870549E+00
# OM= 2.044312994530765E+02 W = 1.264206331660491E+02 Tp=  2455542.055922270287
# N = 1.112777369292801E+00 MA= 1.384785534400715E+02 TA= 1.506929712867154E+02
# A = 9.222822691525098E-01 AD= 1.098541581132661E+00 PR= 3.235148466658604E+02


"99942 Apophis 2011" "Sol"
{

   Class "asteroid"
   Mesh "asteroid.cms"
   Texture "asteroid.jpg"
    Radius  0.248233 
   Albedo            0.7
   RotationPeriod    250.601

   EllipticalOrbit
   {
   Epoch         2455666.5 # A.D. 2011-Apr-15 00:00:00.0000 (CT)
   Eccentricity     1.911121116338028E-01 
   Inclination      3.331912907870549E+00
   AscendingNode    2.044312994530765E+02 
   ArgOfPericenter  1.264206331660491E+02 
   MeanAnomaly      1.384785534400715E+02
   SemiMajorAxis    9.222822691525098E-01
   Period           0.8857353776043806 # 3.235148466658604E+02 days
   }

}

#2462239.500000000 = A.D. 2029-Apr-13 00:00:00.0000 (CT)
# EC= 1.956771467356729E-01 QR= 7.410944262106869E-01 IN= 3.422702257692901E+00
# OM= 2.037856503077860E+02 W = 1.266230059045770E+02 Tp=  2462336.385649814736
# N = 1.114395542439912E+00 MA= 2.520310637199297E+02 TA= 2.325778880870025E+02
# A = 9.213892446335087E-01 AD= 1.101684063056330E+00 PR= 3.230450825492343E+02

"99942 Apophis 2029" "Sol"
{

   Class "asteroid"
   Mesh "asteroid.cms"
   Texture "asteroid.jpg"
    Radius  0.248233 
   Albedo            0.7
   RotationPeriod    250.601

   EllipticalOrbit
   {
   Epoch     2462239.5 # A.D. 2029-Apr-13 00:00:00.0000 (CT)
   Eccentricity    1.956771467356729E-01
   Inclination     3.422702257692901E+00
   AscendingNode   2.037856503077860E+02 
   ArgOfPericenter 1.266230059045770E+02
   MeanAnomaly     2.520310637199297E+02
   SemiMajorAxis   9.213892446335087E-01 
   Period          0.884449233536564 # 3.230450825492343E+02 days
}}



#2464796.500000000 = A.D. 2036-Apr-13 00:00:00.0000 (CT)
# EC= 1.890859232519652E-01 QR= 8.942499762764519E-01 IN= 2.223166114129695E+00
# OM= 2.035175666404274E+02 W = 7.154522286376944E+01 Tp=  2464838.998279122636
# N = 8.510947804859822E-01 MA= 3.238299364591643E+02 TA= 3.082602812502031E+02
# A = 1.102767854101897E+00 AD= 1.311285731927343E+00 PR= 4.229846172883790E+02

"99942 Apophis 2036" "Sol"
{

   Class "asteroid"
   Mesh "asteroid.cms"
   Texture "asteroid.jpg"
    Radius  0.248233 
   Albedo            0.7
   RotationPeriod    250.601

   EllipticalOrbit
   {
   Epoch 2464796.5 #  A.D. 2036-Apr-13 00:00:00.0000 (CT)
   Eccentricity 1.890859232519652E-01 
   Inclination 2.223166114129695E+00
   AscendingNode 2.035175666404274E+02 
   ArgOfPericenter 7.154522286376944E+01
   MeanAnomaly 3.238299364591643E+02
   SemiMajorAxis 1.102767854101897E+00
   Period 1.158068767387759 # 4.229846172883790E+02 days
   }
}

Posted: **16.04.2011, 21:35**

I have created a fictional orbit of Apophis that the asteroid passing Earth by 6.9 km on 14th of april 2062

here is the code:

"2004 MN4 Apophis" "Sol"
{
Class "asteroid"
Mesh "asteroid.cms"
Texture "asteroid.jpg"
Radius 0.248233

EllipticalOrbit
{
Period 0.885712511
SemiMajorAxis 0.921
Eccentricity 0.191
Inclination -0.26
AscendingNode 204.4
ArgOfPericenter 126.4
MeanAnomaly 137
}
Albedo 0.7
RotationPeriod 250.601
}

Posted: **17.05.2011, 23:29**

Close approach on Earth and moon in 2044
I have updated the orbit from Wikipedia

Distance to Earth(closest): 140080 km
Distance to Moon(closest): 151000 km

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Asteroid 2004 MN4 Apophis close to Earth

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Re: Asteroid 2004 MN4 Apophis close to Earth