Hello S.Matthew, The following bug was created that I believe captures what you are experiencing: https://gmat.atlassian.net/browse/GMT-8160
Edwin From: Sharath Mathew <s.mathe...@outlook.com> Sent: Monday, August 4, 2025 4:52 PM To: gmat-developers@lists.sourceforge.net Subject: [EXTERNAL] [BULK] [Gmat-developers] User Issue with Mars Exponential Atmosphere Model CAUTION: This email originated from outside of NASA. Please take care when clicking links or opening attachments. Use the "Report Message" button to report suspicious messages to the NASA SOC. Dear developer(s) of GMAT, I am an avid aerospace enthusiast and just a beginner to the GMAT software, having recently installed it for a project simulating an aerocapture scenario with Mars. I am encountering an issue with the Mars atmosphere model and, after having unsuccessfully tried several options, have decided to write to ask for guidance. I am using the in-built exponential atmosphere model with spherica drag model for my propagator and Rungekutta89 as the integrator. I have my incoming hyperbolic trajectory going deep enough through the Martian atmosphere for atmospheric drag to have a noticeable effect. However, while running the simulation the drag is not taken into account and the spacecraft continues on the hyperbolic path. In the report file, the atmospheric density is displayed as 0 all throughout for all altitudes and there is no effect on acceleration or velocity. I have verified that GMAT is reading the MarsExponentialAtmosphereData.txt file by deliberately messing with the formatting of the contents and receiving the error on the message console. So, I don't suspect the issue to be with the path file or that sort. I have tried doing this on both version 2025a and 2022a. I have tested atmospheric drag effects with Earth using the MSISE90 model and it seems to work fine for up to 100km (going below seemed to be an issue due to the integrator settings, though I've checked strict settings for Mars to no avail). Just as a measure, I replaced the default Mars exponential txt file with simpler values but that also has no effect on the simulation run. I suspect that GMAT is indeed reading the values from the file but for some reason just ignoring them. The parameters for mass, drag coefficient and area are all realistic as well as the force model settings. Could you please advise me on what I'm doing wrong or if I'm missing something? I have tried all this on both the 2025a and 2022a version as stated before but none seem to compute the Martian atmosphere at all. Thank you for your time and support! Yours sincerely, S. Mathew
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