Celestia Forums

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?

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.

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...

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?

Hungry4info wrote: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

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

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.

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

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

Chris, could this be a "modify" bug?

the ssc is as follows for Ceres and Vesta:



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.

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

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

BrianJ wrote: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?

ElChristou wrote: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.

BobHegwood wrote: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...

Hi Bob,

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

txs

ElChristou wrote: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

Derek wrote: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

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

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

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