Rotational parameters for major asteroids

[granthutchison]

I've been looking at asteroid spin information at these two sites:
http://www.astro.amu.edu.pl/Science/Asteroids/Spindata/spin.pdf
http://www.bdl.fr/ephem/ephephys_eng/ephephys_constantes.html
From these its possible to put together some good rotation definitions for solarsys.ssc's four big asteroids, as follows.

CERES

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   Obliquity             11
   EquatorAscendingNode  29
   RotationEpoch    2449249.91125 #1993 Sep 19 09:52:12UT
   RotationOffset       -20.15
   RotationPeriod         9.075


PALLAS

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   Obliquity            102
   EquatorAscendingNode 162
   RotationOffset        -7.23
   RotationPeriod         7.81323264


JUNO

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   Obliquity             56
   EquatorAscendingNode 196
   RotationPeriod         7.811


VESTA

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   Obliquity             40
   EquatorAscendingNode  91
   RotationEpoch    2450124.90833 #1996 May 11 09:48UT
   RotationOffset       145.77
   RotationPeriod         5.342


There's information about most of the rest of the asteroids defined in solarsys.ssc at the second of these sites, but I'd like to look at it for a little longer - I need, for instance, to check whether the pole definitions used for Celestia's mesh objects agree with the pole definitions used in the table at that site.

Grant

[billybob884]

i'll make sure to add these to my list!

[chris]

I'll add the changes into solarsys.ssc for Celestia 1.2.6.

--Chris

[granthutchison]

I've been checking the parameters for Toutatis and Castalia.

TOUTATIS
Toutatis is a retrograde rotator, and appears to precess in the same direction as it spins (at least some of the time!) according to the animation at http://www.solarviews.com/cap/ast/toutspin.htm.
So its rotation parameters should read:

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   RotationPeriod  -129.6 # 5.41 days
   PrecessionRate  -48.98 # 7.35 day period


CASTALIA
I've found an error in the solarsys.ssc orbital period for Castalia, which prevents Celestia reproducing its close approaches to the Earth in 1989 and 2046. I've also corrected the orientation of the shape model relative to its spin axis, given it a polar orientation provided by http://www.astro.amu.edu.pl/Science/Asteroids/Spindata/spin.pdf, and revised the rotation period slightly in the light of the current data from that site and from Horizons.
The final definition I've come up with is:

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"Castalia" "Sol"
{
   Class "asteroid"
   Mesh   "castalia.3ds"
   Texture "asteroid.jpg"
   # We'll just use the same color as Eros
   Color   [ 0.52 0.47 0.42 ]
   BlendTexture true
   Radius  2.0

   EllipticalOrbit
   {
   Period            1.096
   SemiMajorAxis     1.0632007
   Eccentricity      0.48324394
   Inclination       8.88806
   AscendingNode   325.71246
   ArgOfPericenter 121.26355
   MeanAnomaly     152.5186007
   Epoch       2452000.5 #2001 Apr 1 00:00:00UT
   }

   Orientation         [90 1 0 0]
   Obliquity            146
   EquatorAscendingNode 325
   RotationPeriod         4.095

   Albedo            0.15

}


(A single orbit definition is never going to reproduce the close approaches perfectly, but at least they now occur within a few days and a few million kilometres of the correct values.)

Grant

[Darkmiss]

Solarsys Updated
good work as usual, keep it up grant.

Thanks

[granthutchison]

I've now made a sweep through the asteroids in solarsys.ssc.
Scott Hudson's shape models all need reorientated to get their poles on to the Celestia rotation axis. I've tracked down a rotation axis for all of them bar 1998 KY26 (which must have an axis somewhere to go with its shape model - if anyone finds it, let me know), and I've checked most of these against dated rotation animations or radar views, to make sure that the Celestia model is correctly orientated and rotating in the correct sense.
I've also picked up a couple of errors in the Celestia orbit definitions, and updated some rotation periods. Rather than carry on with piecemeal postings, I thought I'd provide a complete current set of definitions for the asteroids. Let me know if you spot any errors!

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# A few main belt asteroids . .
"Ceres" "Sol"
{
   Class "asteroid"
   Texture "asteroid.jpg"
   Radius 456

   EllipticalOrbit
   {
   Epoch      2452600.5 #2002 Nov 22 00:00:00UT
   Period            4.60014
   SemiMajorAxis     2.7660
   Eccentricity      0.0793
   Inclination      10.584
   AscendingNode    80.483
   ArgOfPericenter  74.043
   MeanAnomaly     232.067
   }

   Obliquity             11
   EquatorAscendingNode  29
   RotationEpoch    2449249.91125 #1993 Sep 19 09:52:12UT
   RotationOffset       -20.15
   RotationPeriod         9.075

   Albedo 0.113
}

"Pallas" "Sol"
{
   Class "asteroid"
   Texture "asteroid.jpg"
   Radius 260

   EllipticalOrbit
   {
   Epoch      2452600.5 #2002 Nov 22 00:00:00UT
   Period            4.61868
   SemiMajorAxis     2.7733
   Eccentricity      0.2300
   Inclination      34.846
   AscendingNode   173.166
   ArgOfPericenter 310.423
   MeanAnomaly     218.057
   }

   Obliquity            102
   EquatorAscendingNode 162
   RotationOffset        -7.23
   RotationPeriod         7.81323264

   Albedo 0.159
}

"Juno" "Sol"
{
   Class "asteroid"
   Texture "asteroid.jpg"
   Radius 120

   EllipticalOrbit
   {
   Epoch      2452600.5 #2002 Nov 22 00:00:00UT
   Period            4.35540
   SemiMajorAxis     2.6669
   Eccentricity      0.2589
   Inclination      12.972
   AscendingNode   170.133
   ArgOfPericenter 247.948
   MeanAnomaly     119.146
   }

   Obliquity             56
   EquatorAscendingNode 196
   RotationPeriod         7.811

   Albedo 0.238
}

"Vesta" "Sol"
{
   Class "asteroid"
   Mesh   "vesta.3ds"
   Texture "asteroid.jpg"
   Radius 265

   EllipticalOrbit
   {
   Epoch       2452000.5 #2001 Apr 1 00:00:00UT
   Period            3.62729
   SemiMajorAxis     2.3670775
   Eccentricity      0.089753
   Inclination       7.1346
   AscendingNode   103.9510
   ArgOfPericenter 149.4585
   MeanAnomaly     104.980
   }

   Obliquity             40
   EquatorAscendingNode  91
   RotationEpoch    2450124.90833 #1996 May 11 09:48UT
   RotationOffset       145.77
   RotationPeriod         5.342

   Albedo 0.423
}


# Some of the asteroids visited by spacecraft
"Gaspra" "Sol"
{
   Class "asteroid"
   Mesh "gaspra.3ds"
   Texture "asteroid.jpg"
   #Texture "gaspramosaic.jpg" #Phil Stooke
   Color   [ 0.52 0.47 0.42 ]
   BlendTexture true

   Radius 9.5

   EllipticalOrbit
   {
   Epoch           2448559    #1991 Oct 29: Galileo encounter
   Period          3.2837     #average
   SemiMajorAxis   2.2096348  #at epoch
   Eccentricity    0.1738752  #at epoch
   Inclination     4.0975771  #at epoch
   AscendingNode   253.445592 #at epoch
   ArgOfPericenter 129.045896 #at epoch
   MeanAnomaly     280.769206 #at epoch
   }

   RotationPeriod       7.042073
   EquatorAscendingNode 109.59
   Obliquity            69.28

   RotationOffset       238.86

   Albedo 0.1
}

"Ida" "Sol"
{
   Class "asteroid"
   Mesh   "ida.3ds"
   Texture "asteroid.jpg"
   #Texture "idamosaic.jpg" #Phil Stooke
   Radius 45

   EllipticalOrbit
   {
   Epoch      2449228      #1993 Aug 28: Galileo encounter
   Period          4.8417       #average
   SemiMajorAxis   2.863731     #at epoch
   Eccentricity    0.043109     #at epoch
   Inclination     1.137110     #at epoch
   AscendingNode   324.586055   #at epoch
   ArgOfPericenter 113.017101   #at epoch
   MeanAnomaly     131.594945   #at epoch
   }

   RotationPeriod       -4.633632
   EquatorAscendingNode  172.77
   Obliquity         23.04
   RotationOffset        0.54

   Albedo 0.24
}

"Dactyl" "Sol/Ida"
{
   #Data for Dactyl taken from:
   #Petit et al.: The Long-Term Dynamics of Dactyl's Orbit
   #(Icarus 1997: 130; 177-197)
   InfoURL "http://www.lpl.arizona.edu/~hurfordt/research/papers/Icarus130.pdf"

   Class "asteroid"
   Texture "asteroid.jpg"
   Mesh "roughsphere.cms"
   Radius   0.7

   EllipticalOrbit
   {
   Epoch            2449228.2028 #1993 Aug 28 16:52:05
   Period           -0.96534 #stable 5:1 resonant orbit (Petit et al.)
   SemiMajorAxis    83.5     #stable 5:1 resonant orbit (Petit et al.)
   Eccentricity     0.13     #stable 5:1 resonant orbit (Petit et al.)
   LongOfPericenter 230      #stable pericenter at 90?E Ida longitude (Petit et al.)
   AscendingNode    90       #VERY approximate - chosen to place Dactyl north
                                  #of Ida's equator, as seen at time of Galileo encounter
   Inclination      8        #estimated at 7-9 degrees (Petit et al.)
   }

   RotationPeriod  -23.16816 #enforce synchronous rotation
   RotationOffset  57        #place prime meridian facing Ida

   Albedo 0.2
}


"Eros" "Sol"
{
   Class "asteroid"
   Mesh   "eros5.3ds" #Grant Hutchison
   Texture "asteroid.jpg"
   #Texture "eros2k.jpg" #Grant Hutchison
   # Color sampled from true color photo taken by NEAR
   Color   [ 0.52 0.47 0.42 ]
   # BlendTexture true
   Radius 16.5

   EllipticalOrbit
   {
   Epoch           2451171 #23 Dec 1998: first NEAR encounter
   Period            1.761
   SemiMajorAxis     1.458261
   Eccentricity      0.222885
   Inclination      10.830143
   AscendingNode   304.430882
   ArgOfPericenter 178.613184
   MeanAnomaly     208.403434
   }

   RotationPeriod         5.270
   Obliquity             78.70
   EquatorAscendingNode 107.23
   RotationOffset       158.165

   Albedo            0.16
}


# Radar-imaged asteroids
"Toutatis" "Sol"
{
   Class "asteroid"
   Mesh   "toutatis.3ds"
   Texture "asteroid.jpg"
   # We'll just use the same color as Eros
   Color   [ 0.52 0.47 0.42 ]
   BlendTexture true
   Radius  2.3

   EllipticalOrbit
   {
   Period            3.976715
   SemiMajorAxis     2.5100537
   Eccentricity      0.6342274
   Inclination       0.46959
   AscendingNode   128.24788
   ArgOfPericenter 274.78070
   MeanAnomaly      86.28120
   Epoch        2452200.5 #2001 Oct 18 00:00:00UT
   }

   Obliquity       35
   RotationPeriod  -129.6 # 5.41 days
   PrecessionRate  -48.98 # 7.35 day period
   Orientation     [ 90 1 0 0 ]

   Albedo            0.16
}

"Geographos" "Sol"
{
   Class "asteroid"
   Mesh   "geographos.3ds"
   Texture "asteroid.jpg"
   # We'll just use the same color as Eros
   Color   [ 0.52 0.47 0.42 ]
   BlendTexture true
   Radius  2.555
   InfoURL "http://www-personal.engin.umich.edu/~scheeres/reprints/Icarus_geographos.pdf"

   EllipticalOrbit
   {
   Period            1.39
   SemiMajorAxis     1.2455
   Eccentricity      0.3354
   Inclination      13.34
   AscendingNode   337.352
   ArgOfPericenter 276.756
   MeanAnomaly     180.595
   Epoch       2450800.5 #1997 Dec 18 00:00:00UT
   }

   Orientation       [90 1 0 0]
   Obliquity               136
   EquatorAscendingNode    145
   RotationPeriod            5.223 # from JPL Horizons

   Albedo            0.326 #from JPL Horizons
}

"Kleopatra" "Sol"
{
   Class "asteroid"
   Mesh   "kleopatra.3ds"
   Texture "asteroid.jpg"
   # We'll just use the same color as Eros
   Color   [ 0.52 0.47 0.42 ]
   BlendTexture true
   Radius  109
   InfoURL "http://www-personal.engin.umich.edu/~scheeres/reprints/Science_kleopatra.pdf"

   EllipticalOrbit
   {
   Period            4.67
   SemiMajorAxis     2.791
   Eccentricity      0.2531
   Inclination      13.138
   AscendingNode   215.699
   ArgOfPericenter 179.350
   MeanAnomaly     225.804
   Epoch       2450800.5 #1997 Dec 18 00:00:00UT
   }

   Orientation       [90 1 0 0]
   Obliquity                63
   EquatorAscendingNode    162   

   RotationPeriod         5.385

   Albedo            0.116 #from JPL Horizons
   # Class M

}

"1998 KY26" "Sol"
{
   Class "asteroid"
   Mesh   "ky26.3ds"
   Texture "asteroid.jpg"
   # We'll just use the same color as Eros
   Color   [ 0.52 0.47 0.42 ]
   BlendTexture true
   Radius  0.015

   EllipticalOrbit
   {
   Period            1.3676
   SemiMajorAxis     1.2320798
   Eccentricity      0.20151423
   Inclination       1.48127
   AscendingNode    84.45490
   ArgOfPericenter 209.14766
   MeanAnomaly     356.6879717
   Epoch       2452000.5 #2001 Apr 1 00:00:00UT
   }

   Orientation       [90 1 0 0]
   RotationPeriod       0.178

   Albedo               0.15

}

"Bacchus" "Sol"
{
   Class "asteroid"
   Mesh   "bacchus.3ds"
   Texture "asteroid.jpg"
   # We'll just use the same color as Eros
   Color   [ 0.52 0.47 0.42 ]
   BlendTexture true
   Radius   0.55
   InfoURL "http://echo.jpl.nasa.gov/~ostro/bacchus/index.html"

   EllipticalOrbit
   {
   Period            1.119
   SemiMajorAxis     1.0781035
   Eccentricity      0.34951251
   Inclination       9.43160
   AscendingNode    33.23590
   ArgOfPericenter  55.18040
   MeanAnomaly     229.8627955
   Epoch       2452000.5 #2001 Apr 1 00:00:00UT
   }

   Orientation       [90 1 0 0]
   Obliquity               116
   EquatorAscendingNode    114
   RotationPeriod           14.90

   Albedo            0.15

}

"Golevka" "Sol"
{
   Class "asteroid"
   Mesh   "golevka.3ds"
   Texture "asteroid.jpg"
   # We'll just use the same color as Eros
   Color   [ 0.52 0.47 0.42 ]
   BlendTexture true
   Radius  0.34
   InfoURL "http://www2.crl.go.jp/ka/radioastro/people/koyama/golevka.pdf"

   EllipticalOrbit
   {
   Period            3.995
   SemiMajorAxis     2.5120500
   Eccentricity      0.60117380
   Inclination       2.28701
   AscendingNode   212.16560
   ArgOfPericenter  65.25133
   MeanAnomaly     159.8983670
   Epoch       2452000.5 #2001 Apr 1 00:00:00UT
   }

   Orientation       [90 1 0 0]
   Obliquity               135
   EquatorAscendingNode    292
   RotationPeriod            6.0289
   
   Albedo            0.15

}

"Castalia" "Sol"
{
   Class "asteroid"
   Mesh   "castalia.3ds"
   Texture "asteroid.jpg"
   # We'll just use the same color as Eros
   Color   [ 0.52 0.47 0.42 ]
   BlendTexture true
   Radius  2.0

   EllipticalOrbit
   {
   Period            1.096
   SemiMajorAxis     1.0632007
   Eccentricity      0.48324394
   Inclination       8.88806
   AscendingNode   325.71246
   ArgOfPericenter 121.26355
   MeanAnomaly     152.5186007
   Epoch       2452000.5 #2001 Apr 1 00:00:00UT
   }

   Orientation         [90 1 0 0]
   Obliquity            146
   EquatorAscendingNode 325
   RotationPeriod         4.095

   Albedo            0.15

}


The above code requires my corrected Eros model, which you can download from Selden's site at http://www.lns.cornell.edu/~seb/celestia/hutchison/#4.2
It also works better with the corrected Ida model, again available from Selden's site at http://www.lns.cornell.edu/~seb/celestia/hutchison/#3. (Thanks again to praesepe for doing the smoothing on both these models.) When I've used on-line resources other than the ones I've previously credited, I've supplied an InfoURL in the above listing.

Oh, and belated thanks to Selden, who came up with an albedo for Dactyl!

Grant

[granthutchison]

Oops - meant to include albedos for the Big Four, all supplied by the JPL Horizons system. I've edited the previously posted code.

Grant

[granthutchison]

The final part of solarsys.ssc, with some updated rotational elements (a chaotic tumble for Halley, a good axis and rotation for Borrelly) from me, and a reminder of the previously-posted changes to orbital elements by JackHiggins (which I confess I trimmed of a few decimals).

Code: Select all

# Comets
"Halley" "Sol"
{
   Class "comet"
   Mesh "borrelly.cms" #similar 2:1 proportions to Borrelly
   Texture "asteroid.jpg"
   Radius 7.5

   EllipticalOrbit
   {
   Period        75.31589
   SemiMajorAxis     17.834144
   Eccentricity      0.967143
   Inclination    162.262690
   AscendingNode     58.420081
   ArgOfPericenter 111.332485
   MeanAnomaly     38.384264
   Epoch         2449400.5
}

   #chaotic rotation, imperfectly defined:
   #this version from "The New Solar System", 4th Edition; Eds. JK Beatty, CC Petersen, A Chaikin

   Orientation [90 0 0 1]   # rotates around long axis
   Obliquity 66   
   RotationPeriod  170     # 7.1 day axial rotation period
   PrecessionRate  89    # 3.7 day precession period

   Albedo            0.04
}

"Borrelly" "Sol"
{
   Class "comet"
   Mesh "borrelly.cms"
   Texture "asteroid.jpg"
   Radius 2.2
   InfoURL "http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1256.pdf"

   EllipticalOrbit
   {
   Period 6.86302
   SemiMajorAxis      3.611363
   Eccentricity      0.623908
   Inclination     30.324612
   AscendingNode     75.424869
   ArgOfPericenter 353.375385
   MeanAnomaly     -1.043909
   Epoch        2452174.5
   }

   Obliquity      90
   EquatorAscendingNode    315
   RotationPeriod     25

   Albedo            0.04
}

"Ikeya-Zhang" "Sol"
{
   Class "comet"
   Texture "asteroid.jpg"
   Mesh "roughsphere.cms"

   EllipticalOrbit
   {
   Period       367.181906
   SemiMajorAxis     51.276792
   Eccentricity      0.990111
   Inclination     28.1206
   AscendingNode     93.3718
   ArgOfPericenter  34.6666
   MeanAnomaly      0
   Epoch        2452352.47847
   }

   # These are all made up (copied from Halley)
   Radius 7.5
   RotationPeriod 170
   Albedo 0.04
}

# Centaurs
"Chiron" "Sol"
{
   Class "asteroid"
   Texture "asteroid.jpg"
    Radius 144

   EllipticalOrbit
   {
   Period        50.90359
   SemiMajorAxis     13.734941
   Eccentricity      0.384424
   Inclination      6.927771
   AscendingNode    209.395188
   ArgOfPericenter 339.432152
   MeanAnomaly    -10.016331
   Epoch        2449608.5
   }

   RotationPeriod 5.918

   Albedo 0.048
}

# Kuiper belt objects

# 20000 Varuna
"Varuna" "Sol"
{
   Class "asteroid"
   InfoURL "http://spacewatch.lpl.arizona.edu/2000wr106.html"
   #InfoURL "http://www.ifa.hawaii.edu/faculty/jewitt/papers/VARUNA2/JS2002.pdf"
   Texture "asteroid.jpg"
   Radius 450

   EllipticalOrbit
   {
   Period       284.83446
   SemiMajorAxis     43.290196
   Eccentricity      0.053794
   Inclination     17.12557
   AscendingNode     97.2843
   ArgOfPericenter 275.5744
   MeanAnomaly     82.67171
   Epoch        2452400.5
   }

   RotationPeriod 6.3442 #for a double-peaked light curve

   Albedo 0.4
}

# 2001 KX76
"Ixion" "Sol"
{
   Class "asteroid"
   Texture "asteroid.jpg"
   Radius 600

   EllipticalOrbit
   {
   Period       246.50564
   SemiMajorAxis     39.3138672
   Eccentricity      0.2447032
   Inclination     19.68326
   AscendingNode     71.0155
   ArgOfPericenter 300.9234
   MeanAnomaly    259.585
   Epoch        2452400.5
   }

   Albedo 0.07

   RotationPeriod 30.0
}


although JackHiggins gave radii of 100km for both Varuna and Ixion, the original Celestia radii seem to be on a good footing, and I've therefore restored them in this version. I've also slipped the Borrelly shape model into the Halley definition, since it's of roughly the right proportions, although Halley's primary rotation is around its long axis, whereas Borrelly is in a relatively stable short-axis rotation.

Grant

PS: Edited on 9th February to correct the error detected by DarkMiss, below.

[Darkmiss]

should Haley's Epoch be 449400.5 or 2449400.5

[granthutchison]

should Haley's Epoch be 449400.5 or 2449400.5 :?:

Oops, sorry. 2449400.5.
I just cut-and-pasted those parameters from JackHiggins' original post, so heaven alone knows how I managed to delete that "2"! I'll edit the original post.

Grant

[chris]

All of these updates to solarsys.ssc are now checked into CVS, and will be in 1.2.6 (including that leading 2 )

--Chris

[granthutchison]

(including that leading 2 )

Gad, that's embarrassing. The worst thing, of course, is that I messed up someone else's data, not my own. Sorry, JackHiggins, if you're reading this!

Grant