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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Earth to Mars Transfer using GMAT

I saw a couple of people mention here that in order to change the epoch date from the given Mars transfer example on GMAT I would need to change and re-optimize initial conditions. How would I do that?...
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Non-coplanar transfer in GMAT

I am trying to use GMAT to do a non-coplanar transfer between 2 circular orbits. In which the first orbit would have a 0º inclination, and the final orbit would have a 28º inclination. And the ...
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2 votes
1 answer
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GMAT: What causes the error "ArrayTemplate error : dimension error"?

I have made various scripts that work with GMAT, but once in a while I get an "ArrayTemplate error : dimension error" error. I do not know what causes it, as in this case my script appears ...
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3 votes
1 answer
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GMAT Python API No Convergence

I’m currently using the GMAT Python API in order to set and run my GMAT scripts, but am running into a problem where my scripts do not converge based on certain inputs. Is there a way in the Python ...
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NASA GMAT Hardware in the Loop testing

We are currently evaluating various Mission Analysis & Simulation tools, one of which is NASA's GMAT (2020). One of our requirements is for the tool to support HITL testing. However, i am unable ...
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5 votes
1 answer
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Low-thrust maneuver validation in GMAT

I'm working on a LEO-to-LEO transfer with low-thrust propulsion. I've generated a control sequence with a direct optimization implemented by me and I would like to use GMAT to validate the maneuver. I ...
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Ноw to configure mission sequence for propagate until desired date in GMAT?

In GMAT, I have a state of satellite for a date (for example, 24.04.2022). Now, I need to propagate its motion for some days forward, until selected date (say, 29.04.2022). I added Propagation into ...
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2 votes
2 answers
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Optimizing trajectories with GMAT: how to understand the "Vary" parameters, and how to know what values to use for them?

I've been using GMAT in my free time to optimize trajectories, and have varied burn component values and spacecraft states, usually with success. The vary command in GMAT, with the Yukon optimizer ...
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GMAT: How do I prevent infinite propagation into the future, which causes the "requested epoch 95008.513478505 is not on the DE file" error?

I have a spacecraft I am trying to get from Earth to Mars. I use an Earth propagator until the SC is out of the Earth's sphere of influence, then a deep space propagator until Mars' sphere of ...
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2 votes
1 answer
101 views

Is there any software or other resources that can find optimal launch windows and gravity assist trajectories involving Lagrange points?

I've been using GMAT to make various trajectories involving the Sun-Earth L2 point. Earth-L2-Mars, Earth-L2-Earth flyby-Mars, etc. However, the main source of optimal launch windows I've been using is ...
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2 votes
2 answers
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Is there a parameter that describes the angle between the spacecraft's position and the sun angle or direction of the Earth's motion?

I am trying to design an Earth flyby for gravity assist in GMAT, and I know from theory that the spacecraft should pass in front of a planet with regard to its heliocentric direction of motion in ...
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2 votes
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GMAT: How to Access startup file variables such as PYTHON_MODULE_PATH?

I use the python interface quite frequently and read-in tables of control variables created by another standalone module. I need to be sure that a file created by the standalone python module can be ...
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2 votes
1 answer
116 views

Code to generate Sun-Earth L2 halo orbits for given epoch?

I am working on a GMAT script out of personal interest (not part of a job) that involves a spacecraft orbiting the Sun-Earth L2 point. I have found some orbital state vectors for the spacecraft that ...
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How do I construct halo orbits around the Sun-Earth L2 point in GMAT? What should the state vector of the spacecraft be?

I am new to trajectory design, and have been using GMAT to learn it since it's free, unlike STK. I have been trying to design a script that takes a spacecraft from Earth orbit to a halo orbit around ...
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  • 291
2 votes
1 answer
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GMAT Sun Ephemeris Output

I need the sun's position vector for an analysis, conducted in Matlab. Thus, I let output the ephemeris files for the spacecrafts and additionally I would like to do the same with the sun. A Report ...
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NASA GMAT: Any good tutorials or methods to learn how to use patch points and control points to come up with viable and optimal trajectories?

I'm a beginner to trajectory design, and have to use NASA's GMAT software. It's been a few weeks now, and I have done the first four tutorials and managed to create a (very unrealistic and sub-optimal)...
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  • 291
1 vote
1 answer
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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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1 answer
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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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3 votes
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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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4 votes
0 answers
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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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3 votes
1 answer
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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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1 vote
1 answer
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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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7 votes
3 answers
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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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1 vote
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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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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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1 vote
1 answer
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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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2 votes
1 answer
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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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4 votes
0 answers
42 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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2 votes
0 answers
201 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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1 vote
1 answer
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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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5 votes
1 answer
96 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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8 votes
1 answer
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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 to asking questions on this website). I'm supposed to send a spacecraft from a known GTO to the Moon. A direct ...
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4 votes
1 answer
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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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1 vote
1 answer
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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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2 votes
1 answer
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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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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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1 vote
2 answers
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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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2 votes
0 answers
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GMAT: LEO to GEO with Electrical Thruster simulation?

I would like to get a simulation from LEO to GEO with an electrical Kick-Stage. GMAT seems to be able to do it. Is there any Script/Scenario already written? The aim is to perform a parametric study ...
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0 votes
1 answer
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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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2 votes
1 answer
188 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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4 votes
2 answers
438 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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2 votes
1 answer
142 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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4 votes
0 answers
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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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4 votes
2 answers
319 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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5 votes
2 answers
534 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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5 votes
3 answers
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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2 votes
1 answer
225 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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6 votes
1 answer
240 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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2 votes
0 answers
158 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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3 votes
1 answer
182 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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