Questions tagged [gmat]

Questions about the General Mission Analysis Tool, the program which is designed to model, optimize, and estimate spacecraft trajectories in flight regimes ranging from low Earth orbit to lunar applications, interplanetary trajectories, and other deep space missions.

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26 views

GMAT B-Plane to Mars different date

can anybody help me to find how to change the date to the exercise of GMAT in order to work anyway? I'm not able to solve this problem. Thanks
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1answer
66 views

User help forum for GMAT (General Mission Analysis Tool) users?

GMAT (General Mission Analysis Tool) is an amazing open-source tool for designing spacecraft orbits etc. The latest documentation for GMAT version 2020a says that help is available at http://forums....
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GMAT B-plane Transfer to Mercury

I have been fighting with GMAT for about 3 days now trying to get this transfer to converge so literally ANY assistance and advice would be greatly appreciated. I need to do a direct hohmann like ...
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51 views

How to perform a Hohmann-like transfer to mercury on GMAT

I am trying to simulate a Hohmann-like transfer from Earth to Mercury and establish an orbit there on GMAT. I have the following values already: launch velocity (22.25 km/s) Launch burn (-7.53 km/s) ...
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GMAT: Finite burn targeting, solving for burn duration and quaternion

I'm trying to using GMAT to design a finite burn with a fixed attitude throughout the burn. I do not know the attitude needed at the start, nor do I know the burn duration needed. I set up six ...
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1answer
51 views

Hohmann transfer using GMAT software

I am trying to plot an orbit using gmat. I fixed apogee(RadApo) and perigee(RadPer) for the inner orbit(green) and inserted an impulsive burn. I got the desired shape of the outer orbit but I am ...
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3answers
484 views

Differences between numerical propagators

I am a trainee who is working on a numeric orbital propagator developed in the company. I can't show you the code but I can tell you that the propagator was developed to work in Simulink. My job was ...
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25 views

How to propagate the trajectory in GMAT with a custom thrust profile

So basically I was trying to design a low thrust maneuver to increase the apogee of the spacecraft. I solved it separately and got some thrust profile (thrust and it's direction as a function of time)....
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22 views

How to use the Util and Base Code of the General Mission Analysis Tool

GMAT (General Mission Analysis Tool) provides detailed Util and Base Code, but I don't know how to use it, namely I still don't know how to access so many data of some missions. Can somebody provide ...
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73 views

Using GMAT data to determine satellite elevation angle

I am trying to simulate a communications system between a ground station in Canberra and a satellite in LEO with a $90^{\circ}$ inclination. Specifically, I am interested in the the elevation angle as ...
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1answer
186 views

Trying to run NASA GMAT on Ubuntu 20.04, I get the error "no main manifest attribute, in gmat.jar"

I downloaded GMAT from https://software.nasa.gov/software/GSC-17177-1 Then I extracted using ...
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34 views

How to get GMAT to treat planets as solid objects (that satellites can't pass through)?

I'm running a bunch of trajectories and want some way of stopping calculation on those that intersect the Earth at the time they intersect the Earth. Is there some way to get GMAT to treat Earth (and ...
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121 views

GMAT Orbit Designer

I start to work with GMAT. I am looking into the API capabilites and I found several functions e.g. for the calculation of SSO Orbit Parameters, or Repeating Ground Tracks. So apart from this, is ...
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1answer
81 views

GMAT: Finite Burns commands in If statements inside For loops

Does anyone know why GMAT won't execute finite burns when the BeginFiniteBurn command is placed inside an If statement which is inside a For loop? I'm sure the If condition is verified because there ...
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1answer
89 views

Are the initial conditions for the Apollo PFS objects' orbits known (or knowable) as well as they were for the ascent module?

This answer to Would we have spotted the ascent stage of Apollo 11's Eagle if it was still in orbit around the Moon? and discussion under it suggests that as a check of the orbital propagation ...
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75 views

Using GMAT to simulate phasing orbits with finite burns

I'm working on a project which requires me to use GMAT but I'm new to the program (and asking questions on this website). I'm supposed to send a spacecraft from a known GTO to the Moon. A direct Lunar ...
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1answer
95 views

Why does targeting in the VNB frame lead to a different maneuver magnitude than targeting in an inertial frame?

In GMAT, I set up a targeter (this script) to compute an impulsive maneuver in an inertial frame. The differential correcter finds a maneuver of 3.1161 km/s . If I change the impulsive maneuver to be ...
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1answer
43 views

How to model payload deployment in General Mission Analysis Tool

I just started reading the manuals and doing the tutorials for GMAT. I'd like to use it to model deploying multiple satellites from a launch vehicle and see their resulting orbits. Searching the ...
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29 views

Difference between distance from Mars (Rmag) and B-plane R coordinate

I am running some GMAT simulations on Mars 2020 trajectory to Mars, following the ephemerides published by JPL. I create a target sequence and target the planet using the b-plane coordinates B and T. ...
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37 views

GMAT compilation does not generate gui

I am compiling GMAT 2020a on opensuse linux from source code downloaded from sourceforge. I have gotten the compilation completed. Ran ok, except the /bin ...
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2answers
78 views

GMAT code -- Change animation speed

I find the animations initiated by the run command are so fast that visually I cannot follow them in any detail. I have been unable to find any setting in the program to slow them down. Likewise I ...
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1answer
52 views

Save data in array on General Mission Tool

I have problems for using NASA's General Mission Analysis tool (GMAT). I am trying to save a data in report file (SMA or Semi Major Axis) into a new array. This SMA has 25 lines. I have tried this ...
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1answer
143 views

GMAT: How to do a Hohmann transfer from a larger orbit to a smaller orbit

I've figured out how to do a Hohmann transfer to a larger orbit but can't seem to figure out how to do one back to a smaller orbit (e.g. GEO to random smaller orbit). Any advice would be amazing, ...
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2answers
314 views

GMAT - Locating inter-spacecraft contact instead of spacecraft to ground station

GMAT implements two "event locators" that find eclipse times and line of sight intervals. However, this only lets you analyse data between a ground station and a spacecraft. Is there a way ...
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1answer
94 views

GMAT targeting - why targeting RMAG and DEC works while RadApo and INC doesn't?

The GMAT examples demonstrate targeting using this method for targeting a specific Apoapsis increase maneuver: Vary the prograde speed Apply Maneuver Propagate to the Apoapsis Achieve "the ...
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164 views

How are B-Plane parameters actually determined for a planetary flyby?

Reading from this document, I am trying to simulate the New Horizons probe trajectory in GMAT and I am puzzled with how the authors of the original paper (by legendary mission designer Robert W. ...
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2answers
181 views

Analysing a phasing maneuver using GMAT- how do I reliably quantify their "phase difference"

I am trying to recreate a phasing problem that was solved on paper the previous semester, and verify my solutions using GMAT. Two identical satellites are released on a 550km sun-synchronous orbit by ...
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2answers
352 views

How to create a satellite intersection/conjunction in GMAT?

Starting to learn GMAT. I've been able to get my satellite to move around in space pretty well with various targets and maneuvers in the mission sequence. Now I would like to have my satellite target ...
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3answers
1k views

Why does a satellite with a higher mass fall slower?

I was doing simulations in GMAT and I could observe that if I increase the mass of the satellite, the satellite falls slower ... and if I reduce the mass of the satellite, then it falls faster (I only ...
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1answer
194 views

Error in Propagating equatorial orbit using GMAT

I propagated an orbit with semi-major axis of 7000km and the rest of the keplerian orbital elements 0 on GMAT. Since the orbit is circular and in the Equatorial plane, it should not change over time. ...
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1answer
169 views

How to design a lunar flyby trajectory in GMAT?

I am trying to design a flyby mission to the moon using electric propulsion on GMAT. I've gone through the tutorials, however, the most useful one "Lunar Flyby to the moon using multiple shooting&...
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117 views

What programs simulate the orbit of an asteroid over long periods of time?

I am trying to simulate the orbit of an asteroid over a long period of time in order to see the change in the orbit due to a constant force applied to the asteroid. Initially, I used GMAT to simulate ...
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1answer
167 views

Orbit transfer trajectory options to the moon

I am working on a project for a lunar flyby using a CubeSat. I was wondering what kind of trajectory transfer options are present and which one would be best for a CubeSat? I'm aiming for a transfer ...
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273 views

Model multi-stage lunar transfer on GMAT?

I am new to GMAT, and I am wondering if it is possible to simulate a multi-stage lunar transfer on GMAT? The mission sequence I am hoping to model is a low earth orbit, followed by a trans-lunar ...
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143 views

Using Differential Equations to model path of satelite around earth

I am new to GMAT and am hoping to use it to model the path of a Low Earth Orbit satellite around Earth. I am thinking of plotting the path on a plane and using polar coordinates to model the path ...
3
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1answer
250 views

NRLMSISE atmospheric drag model in GMAT

I'm using GMAT (R2018a) software for orbital propagation and now testing the atmospheric drag. There are only 2 options: JacciaRoberts and MSISE90. Is there a way to add NRLMSISE00 to the options? ...
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1answer
374 views

Spherical solar radiation model (GMAT)

I'm using GMAT to analyze the orbits. There is a Spherical model for Solar Radiation Pressure. Which equation does GMAT use to calculate it? I've already searched in the documentation, however, there ...
4
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1answer
866 views

How open is NASA's "open source" GMAT software?

In answers and comments to What does it mean when a software is called open-source for US-release only? I found out that when NASA uses the term "open source" it does not mean open to everyone! ...
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1answer
407 views

GMAT atmosphere

I am using GMAT to propagate satellite motion with Jacchia-Roberts atmosphere model. Here is a formula used from this model which is then used to estimate the variation in drag on a spacecraft due to ...
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2answers
635 views

Earth geopotential effect on orbit propagation

I'm trying to take into account the Earth geopotential effect on the orbit. The only term I could consider, is J2. Are the terms (J2, etc.) change with time? I ...
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1answer
170 views

Comparison of AOP change of the orbits

I'm comparing how the Argument of perigee (AOP) changes for 2 orbits (O1 and O2). The orbits ...
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1answer
751 views

Low Earth orbit propagation in GMAT

I'm propagating a Low Earth orbit using GMAT. I 'm trying to make the propagation realistic, considering the zonal harmonics, Sun, Moon, Jupiter, Venus perturbations, tidal forces and solar ...
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1answer
1k views

Brouwer-Lyddane mean semi major axis bias

I'm using the software GMAT (General Mission Analysis Tool) (website, YouTube) for propagating spacecraft and calculating their Brouwer-Lyddane (BL) mean semi-major axis (SMA). I found out something ...