Dawn mission addon

[CAP-Team]

I was looking for a Dawn mission addon, but couldn't find much, so I decided to open a topic here.

Through NASA's Horizons system I derived the ephemerides and I created a SSC file.

You can download them here

Does anyone have a model for the spacecraft?

[CAP-Team]

I've updated the addon, it now contains the entire Dawn mission from 2007 to february 2015. Sampled orbits for Ceres and Vesta are also included.

[Tomasz M. Bladyniec]

Thank you very much! However, there is some bug in "modify" function of asteroids in your .ssc file. After initiating Celestia, Vesta and Ceres seem to be old ones...

[Hungry4info]

The ssc file visits both of the asteroids within a few million kilometres, but doesn't actually go into orbit around them =( Is this the true orbital path of dawn? i.e. are the Vesta and Ceres encounters just flybys?

[chris]

The ssc file visits both of the asteroids within a few million kilometres, but doesn't actually go into orbit around them =( Is this the true orbital path of dawn? i.e. are the Vesta and Ceres encounters just flybys?

No, that's not correct: Dawn will orbit both Vesta and Ceres. It's possible that the exact orbits at the asteroids aren't known yet, and thus not in the trajectory. I'm downloading the add-on now to have a look.

--Chris

[chris]

Some details on the orbits at Ceres and Vesta:

http://www-ssc.igpp.ucla.edu/dawn/mission.html

* Delta 7925H launch; 3 Xenon (Xe) ion thrusters, DS1 heritage
* Cruise: one thruster at a time
* Vesta: orbit at 2450, 700 and 200 km alt. 7 months incl. orbit changes
* Ceres: orbit at 5900, 1300 and 700 km alt. 5 months incl. orbit changes
* 275 kg Xe to Vesta; 110 kg to Ceres for maximum injected mass
* Orbit captures, orbit transfers and Vesta escape with ion propulsion

--Chris

[CAP-Team]

If you run the simulation, Dawn will come very close to Vesta (about 3000 km) but it will not orbit Vesta but stay very close to it for months. At Ceres, it will pass very close to Ceres.

But I can imagine that the final orbits aren't implemented in the ephemerides yet.

[chris]

I was curious about Dawn's orbital period at Ceres:

5900 km: 4 days, 16 hours
1300 km: 16 hours, 31 minutes
700 km: 8 hours, 55 minutes

This assumes a mass for Ceres of 9.43*10^20 kg and a circular orbit. When the complete trajectory does become available on HORIZONS, you'll want to decrease the time step (currently 3 hours) for the 1300km and 700km orbits.

Thanks for making this add-on available!

--Chris

[Hungry4info]

When I ran it, it never got to within a million kilometres of Vesta.

[CAP-Team]

Chris, could this be a "modify" bug?

the ssc is as follows for Ceres and Vesta:

Code: Select all

modify "Ceres" "Sol" {

  Beginning  "2007 09 28 00:00:00"
  Ending     "2016 01 01 00:00:00"
  SampledOrbit "ceres.xyz"

}

modify "Vesta" "Sol" {

  Beginning  "2007 09 28 00:00:00"
  Ending     "2015 02 01 00:00:00"
  SampledOrbit "vesta.xyz"
 
}


It works fine on my system, but that is probably because I updated the keplerian elements of the orbits of Ceres and Vesta in asteroids.dat for about the time Dawn will visit the bodies.

Code: Select all

"Ceres" "Sol"
{
  Class           "asteroid"
  Texture         "asteroid.jpg"
  Color           [ 1.000 0.945 0.881 ]
  BlendTexture    true
  Radius                 487.5        # 975x909km
  Oblateness               0.068      # Thomas et al, Nature, 8 Sep 2005
  Albedo                   0.090

  InfoURL "http://en.wikipedia.org/wiki/Ceres_%28dwarf_planet%29"

  EllipticalOrbit {
    Epoch            2457068.5        # 2015 Feb 15 00:00 UT
    Period                 4.6042995727713
    SemiMajorAxis          2.76763649328599
    Eccentricity           0.0758241207709475
    Inclination           10.5930906235048
    AscendingNode         80.3291511905271
    ArgOfPericenter       72.5598483052138
    MeanAnomaly          110.506230919313
  }

  UniformRotation {
    Epoch            2449249.91125    # 1993 Sep 19 09:52:12 UT
    Period                 9.074170   # Icarus 2007,188(2):451
    Inclination           11
    AscendingNode         29
    MeridianAngle        339.85
  }
}


Code: Select all

"Vesta" "Sol"
{
  Class           "asteroid"
  Mesh            "vesta.cmod"
  MeshCenter      [ 0.77 3.424 -0.554 ]
  Texture         "asteroid.jpg"
  Color           [ 1.000 0.923 0.851 ]
  BlendTexture    true
  Radius                 265          # maximum semi-axis
  Albedo                   0.4228
 
  InfoURL "http://en.wikipedia.org/wiki/4_Vesta"

  EllipticalOrbit {
    Epoch            2455788.5        # 2011-08-15 00:00 UT
    Period                 3.6282880753642
    SemiMajorAxis          2.36120942258714
    Eccentricity           0.0883162904551309
    Inclination            7.1346174750964
    AscendingNode        103.9043478888040
    ArgOfPericenter      149.8778686365480
    MeanAnomaly           53.146250452834
  }

  UniformRotation {
    Epoch            2450124.90833   # 1996 May 11 09:48UT
    Period                 5.342
    Inclination           40
    AscendingNode         91
    MeridianAngle        325.77
  }
}


[RVS]

By the way, Dawn model for Orbiter DO exists almost a year, but not for Celestia…

[BrianJ]

Hello
since the Orbiter community has benefited hugely from work done for Celestia in the past, I thought the least I could do was to offer my "Dawn" model for use by whoever would like it.

I've converted it to .3ds format with .jpg textures, scale is in meters. I'm afraid I don't know how to package it as a Celestia add-on - if anybody wants to do that and upload somewhere for public use, that's fine.

You can download the .zip file here(0.6Mb)
http://myweb.tiscali.co.uk/briansutilit ... wn_3DS.zip

Regards,
Brian

[ElChristou]

Hello
since the Orbiter community has benefited hugely from work done for Celestia in the past, I thought the least I could do was to offer my "Dawn" model for use by whoever would like it.

I've converted it to .3ds format with .jpg textures, scale is in meters. I'm afraid I don't know how to package it as a Celestia add-on - if anybody wants to do that and upload somewhere for public use, that's fine.

You can download the .zip file here(0.6Mb)
http://myweb.tiscali.co.uk/briansutilit ... wn_3DS.zip

Many Tx for this kind donation!
You say you have converted the model to 3ds, but if I'm not wrong it's a an8 file in your zip... Should we just change the extension?

[BobHegwood]

Many Tx for this kind donation!
You say you have converted the model to 3ds, but if I'm not wrong it's a an8 file in your zip... Should we just change the extension?

Christophe,

Just open the .an8 file using Anim8or... Then export the file to a .3ds model file. Works very easily.
Thanks, Bob

EDIT: Or, I can do this and e-mail a copy of the 3ds file to you if you don't have the Anim8or. Just let me know.

[ElChristou]

EDIT: Or, I can do this and e-mail a copy of the 3ds file to you if you don't have the Anim8or. Just let me know.

Yes, would be cool because on osX we have nothing called Anim8or...

[Derek]

Hi Bob,

Tried your instructions somehow finished up with a white sphere so would appreciate a copy of your file.

txs

[BrianJ]

You say you have converted the model to 3ds, but if I'm not wrong it's a an8 file in your zip...

Doh! You are quite correct....I have changed it to .3ds now, download on the same link as before.

Cheers,
Brian

[BobHegwood]

Hi Bob,

Tried your instructions somehow finished up with a white sphere so would appreciate a copy of your file.

txs

The problem is that Brian's 3ds model is looking to pull its textures from Brian's desktop. Obviously, this will not do when the model is processed in Celestia.
I haven't downloaded the new model yet, but even if it is still doing this, all that is required is to revise the model to pull its textures from a textures\medres folder in order for it to work correctly.

Thanks, Bob

[ElChristou]

Yep, the textures don't shows up because of the tree.

Brian, nice model! It's your own creation?

[BobHegwood]

Christophe?

I have e-mailed the converted package in its entirety to you. I re-packaged it a bit just to save you some work too.
You'll see the 3ds file in the models directory, and the textures in the textures\medres directory. Go read your mail, son.
You have LOTS of stuff cluttering up your mail box now.

Thanks, Bob