Hi Edwin, The problem is definitely the bug in the link provided by Sharah. I make some simulation but even reducing the MAVEN spacecraft near Mars or even puting puting the earth atmosphere model to the mars atmosphere data I still get 0. I suggest using AGI STK. You can get a free trial for 14 days. Here is the link https://www.agi.com/products
Le mer. 6 août 2025 à 10:25, Sharath Mathew <s.mathe...@outlook.com> a écrit : > Hi Edwin, > > Thanks for letting me know. What would you advise is the best course of > action at the moment? Is there some kind of alternative / different > approach to achieve the drag effects on Mars? > > > ------------------------------ > *From:* Dove, Edwin (GSFC-5950) <edwin.d...@nasa.gov> > *Sent:* 05 August 2025 15:38 > *To:* Sharath Mathew <s.mathe...@outlook.com>; > gmat-developers@lists.sourceforge.net < > gmat-developers@lists.sourceforge.net> > *Subject:* RE: [Gmat-developers] User Issue with Mars Exponential > Atmosphere Model > > > 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 > > > _______________________________________________ > GMAT-developers mailing list > GMAT-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/gmat-developers > -- *Moussa FALL* ing Polytechnicien de Conception en Informatique et Télécom*, *Spécialiste dans le développement de systèmes spatiaux *.*
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