Calling libration point position wrt Earth position?

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Calling libration point position wrt Earth position?

Postby hornig » Thu Mar 07, 2013 4:45 pm

Hi there,

another question from my side.
I need to know the distance between the libration point L4 with respect to the Earth. I want to include phasing and need to know if the current radius of the spacecraft is bigger than that of the libration point and I could also need it to determine the direction in which the phasing is fastest.

I couldn't call the positions from the reference frame centers of Earth and the libration point. Is that possible somehow?

Best regards,


Andreas
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Re: Calling libration point position wrt Earth position?

Postby jjkparker » Fri Mar 08, 2013 2:06 pm

Andreas,

GMAT doesn't currently let you directly get the positions of the things in SolarSystem (planets, moons, libration points...). But, see the following topic for a workaround:

http://gmat.ed-pages.com/forum/viewtopic.php?f=50&t=43554

Let me make sure there's an enhancement request in the system for this feature...

Joel
Joel J. K. Parker
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http://gmatcentral.org
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Re: Calling libration point position wrt Earth position?

Postby jjkparker » Fri Mar 08, 2013 2:08 pm

Yep, the request is in the system:

http://li64-187.members.linode.com:8080/browse/GMT-3516

Feel free to comment on it, if you'd like.
Joel J. K. Parker
Flight dynamics engineer, GMAT team
http://gmatcentral.org
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Re: Calling libration point position wrt Earth position?

Postby hornig » Fri Mar 08, 2013 3:19 pm

Hi,

I already found a solution but I consider that as a work around because the script has to be calculated during the run and only causing additional operations for something that's already inside ;).
But at least it works.

Best regards, Andreas

Code: Select all
GMAT LunaPosX = DefaultSC.EarthMJ2000Ec.X-DefaultSC.LunaMJ2000Ec.X;
GMAT LunaPosY = DefaultSC.EarthMJ2000Ec.Y-DefaultSC.LunaMJ2000Ec.Y;
GMAT LunaPosZ = DefaultSC.EarthMJ2000Ec.Z-DefaultSC.LunaMJ2000Ec.Z;
GMAT EM_RMAG = sqrt(LunaPosX*LunaPosX+LunaPosY*LunaPosY+LunaPosZ*LunaPosZ);
GMAT RadialDistanceToMoon = DefaultSC.Earth.RMAG-EM_RMAG;

GMAT GammaAngle = acos((LunaPosX*DefaultSC.EarthMJ2000Ec.X+LunaPosY*DefaultSC.EarthMJ2000Ec.Y+LunaPosZ*DefaultSC.EarthMJ2000Ec.Z)/(sqrt(DefaultSC.EarthMJ2000Ec.X^2+DefaultSC.EarthMJ2000Ec.Y^2+DefaultSC.EarthMJ2000Ec.Z^2)*sqrt(LunaPosX^2+LunaPosY^2+LunaPosZ^2)))*180/3.1615;
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Re: Calling libration point position wrt Earth position?

Postby shughes » Tue Apr 09, 2013 4:46 pm

I agree this is a workaround and not ideal behavior. I put in a feature request here: http://li64-187.members.linode.com:8080/browse/GMT-3819#comment-23928
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Re: Calling libration point position wrt Earth position?

Postby hornig » Thu Jun 06, 2013 1:40 pm

Hi,

is this feature now implemented in the current version of GMAT?
I'm afraid to update my version and not be able to work with my old scripts anymore ;).
But I would like to output the locations from earth and moon for a blender animation we will do.

Best regards,

Andreas
hornig
 
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Joined: Fri Nov 30, 2012 3:16 pm

Re: Calling libration point position wrt Earth position?

Postby shughes » Thu Jun 06, 2013 1:53 pm

We are currently implementing this feature and it is not in the current release. I hope that we can publicly release these features in early July.
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Re: Calling libration point position wrt Earth position?

Postby hornig » Sat Jun 08, 2013 10:15 am

shughes wrote:... I hope that we can publicly release these features in early July.


damnit, I would need it now to use it for the Blender animation for my thesis presentation in the next weeks :).
Hmmm, Perhaps I will have to do a workaround :(.

Andreas
hornig
 
Posts: 28
Joined: Fri Nov 30, 2012 3:16 pm


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