Synchronization of Sats for OpenGL plots

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Synchronization of Sats for OpenGL plots

Postby dcmrr » Thu Sep 11, 2008 10:31 pm

We are working on a Phase-1 project for space target surveillance and using GMAT for visualization. We are currently meeting a problem on displaying satellites with different epochs in one scene as GMAT will give an error message when we try to display satellites with different epoch time. Can anyone tell us if GMAT have any internal function to synchronize these satellites before displaying them? If not, where we can get some help to synchronize these satellites before displaying them with GMAT?

thanks,
DCM
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Re: Synchronization of Sats for OpenGL plots

Postby space_egd » Fri Sep 12, 2008 1:34 pm

Hello DCM,

Welcome to the GMAT forums and thanks for posting some feedback on your GMAT experience.
I've gone ahead and moved your topic to the Help Forum.

As you've discovered GMAT's OpenGL plots can't display spacecraft with different epochs at the same time and doesn't implement logic to automatically sync the spacecraft. The user has to sync the spacecraft together before being able to properly display all satellite at the same time. The Propagate command also doesn't propagate Satellites if the start off with different epochs.

I'm assuming you are using the 12/10/2007 Build of GMAT on Windows, so that's the build I'm using to help troubleshoot. We should have a new executable available to the public this month.

I've attached an Unsynchronized satellite propagation script to see if you are getting the same message. When you Build&Run UnsyncedSC.script, the following error message appears:
Code: Select all
**** ERROR **** Command Exception: Epochs are out of sync on Propagation line:
"Propagate DefaultProp(SC1, SC2) {SC1.ElapsedDays = 5}"


Is this the same error message you get?

OR

Are you experiencing behavior as seen in the UnsyncedSC2.script file?
When you Build and Run this script you see that one spacecraft propagates first then the other even though their Epochs aren't that different. There is no error/warning message displayed in this case.
Attachments
UnsyncdSC2.script
(1.41 KiB) Downloaded 147 times
UnsyncdSC.script
(1.37 KiB) Downloaded 165 times
Last edited by space_egd on Fri Sep 12, 2008 6:10 pm, edited 1 time in total.
Reason: Added text about Propagate command not auto syncing sats
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Re: Synchronization of Sats for OpenGL plots

Postby space_egd » Fri Sep 12, 2008 2:10 pm

Either way I've attach a script called Unsyncd2SyncedSC.script that shows two ways of synchronizing the SC which would allow them to be displayed without error.

In the script, I propagated one satellite to match the epoch of another satellite, then propagated both of them with the same Propagate Command for 5 days. The first propagate command will result in different step sizes for each SC but the final stopping condition will be achieved by both. You shouldn't get an error message for the OpenGL even though the intermediate propagation steps for each satellite is different. Mostly likely you won't be able to tell that the spacecraft are stepped at different times. In the second Propagate command both spacecraft are propagated at the same step size and would result in a truly sync'd evolution of time in the OpenGL plots.

Hope this helps.
For definitions and brief descriptions to the commands and objects in GMAT as well as some tutorials, visit the GMAT wiki at http://gmat.ed-pages.com/wiki/
Propagate Command
Attachments
Unsyncd2SyncedSC.script
(1.82 KiB) Downloaded 176 times
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Re: Synchronization of Sats for OpenGL plots

Postby dcmrr » Fri Sep 12, 2008 6:28 pm

Edwin:

Thanks. The problem is solved by your Unsyncd2SyncedSC.script.

DCM
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Re: Synchronization of Sats for OpenGL plots

Postby space_egd » Fri Sep 12, 2008 6:51 pm

No problem. Glad I could help.

Let us know if there are any other issues you come across, big or small.
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