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Orbit Determination

PostPosted: Mon Jun 06, 2011 5:48 am
by psoni
Hello to all
I want to know how to add measurement data ( Range from a ground station) collected from a ground station. I am using beta version on windows but GMAT does not provide any icon in least square block to assign measurement data. I also wana to know which measurement format GMAT accepts.

Re: Orbit Determination

PostPosted: Fri Jun 24, 2011 3:41 pm
by DJCinSB
Hi, Pramod.

One preliminary step: in order to play with GMAT's estimation code, the estimation plugin needs be loaded. That happens if you uncomment this line in your gmat_startup_file.txt:
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#PLUGIN                 = ../plugins/libGmatEstimation

Change it to this:
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PLUGIN                 = ../plugins/libGmatEstimation

(You may have done this already, but I wanted to be sure!)

Right now the OD part of GMAT is very much a preliminary component. We only read an internal data format at the moment, but that format is pretty simple to generate. The file is an ASCII text file, with one measurement per line. A measurement looks like this:
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21545.24074074074    GeometricRange    7000    MauiID    ODSatID    3239.83576

The data has this arrangement: [a.1 Modified Julian epoch] [Measurement type] [Measurement type ID] [Station ID] [Spacecraft ID] [Measurement data]

There is a sample data file in the output folder that comes with the R2011a release; look for the file "Maui_GeometricRange.gmd". This file is processed by the sample mission Estimate_LEO_Batch_GeometricRange.script, which you can find in the samples/PreliminaryEstimation folder. That folder also contains several scripts that generate simulated measurement data for measurement types that GMAT knows at this time. The generated data files follow this same format, so you should be able to see how GMAT expects the data by running those scripts and opening the resulting files.

I hope that helps!

- Darrel