the python script is on Gitlab This example uses Tian He core stage as example, NORAD id is 48275, so the TLE text file is named as 48275.txt 1. prepare a text file with 3 lines first line : TIANHE_CORE second and third line: TLE run "anaconda prompt" goto directory where the python script is located type 48275.txt | python TLE2Keplerian.py > out.txt the keplerian elements are now saved in the out.txt file. using myfirst.script as template, replace keplerian element lines with the data just generated copy and paste the output into another text file, named as 48275.script these lines are kept the same every time: GMAT $$$$$.DateFormat = UTCGregorian; GMAT $$$$$.Epoch = '01 Jan 2000 11:59:28.000'; GMAT $$$$$.CoordinateSystem = EarthMJ2000Eq; GMAT $$$$$.DisplayStateType = Keplerian; replace $$$$$ with name of your satellite run GMAT File >New >Mission File > Open> myfirst_48275.script press the run button or press F5: if everything is ok, you will th...