Configuring Data Files

You can configure the data files GMAT loads at run time by editing the gmat_startup_file.txt file located in the bin directory. The startup file contains path information for data files such as ephemeris, Earth orientation parameters and graphics files. By editing the startup file, you can customize which files are loaded and used during a GMAT session. Below we describe the customization features available in the startup file. The order of lines in the startup file does not matter.

For all details, see the Startup File reference.

Leap Second and EOP files

GMAT reads several files that are used for high fidelity modelling of time and coordinate systems: the leap second files and the Earth orientation parameters (EOP) provided by the IERS. The EOP file is updated daily by the IERS. To update your local file with the latest data, simply replace the file eopc04_08.62-now in the data/planetary_coeff directory. Updated versions of this file are available from the IERS.

There are two leap second files provided with GMAT in the data/time directory. The naif0010.tls file is used by the JPL SPICE libraries when computing ephemerides. When a new leap second is added, you can replace this file with the new file from NAIF. GMAT reads the tai-utc.dat file for all time computations requiring leap seconds that are not performed by the SPICE utilities. When a new leap second is added, you can replace this file with the new file from the US Naval Observatory. In addtion, you can modify the file if a new leap second is added by simply duplicating the last row and updating it with the correct information for the new leap second. For example, if a new leapsecond were added on 01 Jul 2013, you would add the following line to the bottom of tai-utc.dat:

2013 JUL 1 =JD 2456474.5 TAI-UTC= 35.0 S + (MJD - 41317.) X 0.0

Loading Custom Plugins

Custom plugins are loaded by adding a line to the startup file (bin/gmat_startup_file.txt) specifying the name and location of the plugin file. In order for a plugin to work with GMAT, the plugin library must be placed in the folder referenced in the startup file. For all details, see the Startup File reference.

Configuring the MATLAB Inteface

GMAT contains an interface to MATLAB. See the MATLAB Interface reference to configure the MATLAB interface.

User-defined Function Paths

If you create custom MATLAB functions, you can provide the path to those files and GMAT will locate them at run time. The default startup file is configured so you can place MATLAB functions (with a .m extension) in the userfunctions/matlab directory. GMAT automatically searches that location at run time. You can change the location of the search path to your MATLAB functions by changing these lines in your startup file to reflect the location of your files with respect to the GMAT bin folder:

MATLAB_FUNCTION_PATH = ../userfunctions/matlab

If you wish to organize your custom functions in multiple folders, you can add multiple search paths to the startup file. For example,

MATLAB_FUNCTION_PATH = ../MyFunctions/utils
MATLAB_FUNCTION_PATH = ../MyFunctions/StateConversion 
MATLAB_FUNCTION_PATH = ../MyFunctions/TimeConversion

GMAT will search the paths in the order specified in the startup file and will use the first function with a matching name.