# 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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### GMAT Lambert problem

I would like to plan a mission in GMAT to a certain asteroid, whose orbit and SPK file I have added in GMAT. However, I don't know how to solve the Lambert problem in it to first find the intersection ...
1 vote
44 views

### Interpreting phasing maneuver results using electric propulsion in GMAT

I'm trying to simulate an anomaly phasing maneuver in three different scenarios using electric propulsion in GMAT. The idea is to use the altitude difference (of ~7-8km) between two spacecrafts to ...
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1 vote
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### It is possible to perform a simplified version of rpo with GMAT?

I have one target vehicle and a chaser. How can I perform an orbit transfer with GMAT but, at the end of the transfer this finished maintaining a relative position of 1000 m behind the target and 1000 ...
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### Example using NASA GMAT to model a sounding rocket launch

I'm wondering if anyone has an example GMAT script that describes a sounding rocket launch and return. Not necessarily looking for high fidelity but just something that shows the parameters for a ...
110 views

### How do I programmatically change the GMAT Mission Sequence?

This is a niche technical question about using the GMAT API. After digging through all of the official GMAT documentation and videos, I finally decided to use my Java application as a script driver ...
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### NASA GMAT sample script providing deltaV above analytical result when aiming to GEO Height

I am using the GMAT example script available at \samples\Ex_GEOTransfer.script (R2022a) to compute de deltaV from LEO to GEO including change plane maneuver. The problem is that the script seems to be ...
1 vote
225 views

### Change in True Anomaly over time

From Wikipedia, the True anomaly is defined as the angle between the direction of periapsis and the position of the celestial body. I'm trying to find how the true anomaly changed over time for a ...
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### How to make a velocity(time) XYplot graph in NASA's GMAT R2022?

I'm wondering how to design a graph in NASA's GMAT (Version R2022a), which shows satellite's linear velocity on time or on altitude from primary body (Earth). When I open the XYplot design window ->...
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### Difference between UTCGregorian and A1ModJulian or UTCModJulian in GMAT?

I have a question related to this question. I have computed several propulsive maneuvers required for GEO orbit acquisition using the Target feature of NASA GMAT 2022a and saved them to a maneuver ...
98 views

### Showing what satellites can "see" in GMAT

I'm currently working on orbit modeling in GMAT and I'm interested in visualizing the satellite's visibility on the ground track. Is there a feature or tool within GMAT that allows for the ...
273 views

### GMAT LEO spacecraft simulation

I started using GMAT, I have to design an LEO of an AEOLUS Satellite and I have the TLE of the launching. My question is how do I plug the TLE numbers into the spacecraft section (Keplerian element ...
1 vote
139 views

### Accessing propagation results when running a GMAT script with Python API

I am using the GMAT Python API to run scripts, fx the Ex_R2022a_TLE_Propagation.script can be used as an example, as this is included in GMAT/samples. ...
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109 views

### Difference Result of Numerical Satellite Propagator

Currently, I am trying to build a numerical propagator platform for satellite that accommodates for all kinds of perturbation. So, for validation purpose, I compare the result of my own program and ...
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784 views

### Setting up and using Python interface in GMAT?

I have managed to successfully setup and use the MATLAB interface in GMAT, with a combination of the documentation and this helpful video, which gave me all the information I needed. Alas, that is not ...
1 vote
153 views

### How to get contact locator events in GMAT using Python

I am trying to write a python script for GMAT to detect contacts between a satellite and a ground station. I have declared the contact locator as such: ...
101 views

### Beginner to simulating communications systems of space missions. I have GMAT, MATLAB and NASA's SPICE library. Where would I start?

I recently managed to load SPICE kernels into GMAT to simulate the trajectories of real missions, and got its MATLAB interface working (still trying to understand how to use the two software together)....
419 views

### Different Earth-centered ICRF positions in GMAT and Skyfield/Spiceypy with DE421

I compared the Earth-centered positions from the Moon in the ICRF (i.e., in GCRF) using three different sources: SpiceyPy (https://pypi.org/project/spiceypy/) Skyfield (https://rhodesmill.org/...
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### How to model the gravity of Titan in GMAT

I would like to know how to find the gravity file (.cof) for Saturn's moon Titan. Need this to model the gravity field of Titan.
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### Running and editing GMAT script files from MATLAB

I am trying to run a design optimisation proccess for some orbital parrameters of spacecraft. To do this, I need to be able to edit and run a GMAT script from MATLAB. Is this possible? If so, how ...
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1 vote
127 views

### How to perform a Burn Operation in GMAT via python api

'm testing the python api of GMAT (2022). I'm able to instantiate a satellite object and do propagation in steps. I would like to include an instant burn operation in the simulation, but the code just ...
1 vote
197 views

### Circularization of an orbit on gmat

I'm using Gmat to turn to zero the eccentricity of an orbit around Mars with an electric thruster. I modeled the initial orbit, introduced the engine, the tank and the solar arrays and created the ...
1 vote
72 views

### How to compute light time correction for eclipse entry/exit timings?

I used a typical geosynchronous orbital parameters and generated lunar shadow penumbra entry and exit timings using OREKIT and GMAT. GMAT has an option to include light-time correction (also for ...
265 views

### GEO station keeping in GMAT

I am currently trying to implement station keeping maneuvers for a geosynchronous satellite in orbit around Earth using the General Mission Analysis Tool (GMAT) but I am not managing. I know there are ...
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### Approach to Interplanetary Transfers in GMAT

I hope to find a straightforward process for designing interplanetary missions using the General Mission Analysis Tool (GMAT). This would involve calculating the required initial state, timing, and ...
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1 vote
100 views

### GMAT Get States of Propagation

I am failing with the most simple thing ever: I want to store the SC states of a Propagation over 1 day inside an array! So the basic script would look like this: ...
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### Can we have launch trajectories in GMAT?

Is it possible to model launch trajectories from ground to a certain earth orbit in GMAT?
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### New to GMAT. Where do I start to build an orrery?

The goal would be an animated, variable-speed, 2-D view from celestial north of the Sun and planets. A stretch goal would be showing photorealistic rotations of CelestialBodys as a function of time. I ...
137 views

### Mathematical description of the flight trajectory parameters of voyager 1

I would like to run in some simulation software an end-to-end simulation replicating the flight of voyager 1. I am somewhat conversant with GMAT that I think would have this capability or perhaps ...
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1 vote
84 views

### Initial Value in Vary Command (GMAT)

What number should I give as an initial value in GMAT's Vary command? I have been trying to use default values but in some missions this default value does not lead to the convergence of target or ...
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1 vote
234 views

### How to propagate satellite to orbit intersection (relative node) in GMAT? [closed]

I am trying to propagate the spacecraft to the intersection points of two orbits (relative node) in GMAT. The analytical calculations of the true anomaly of that point is done using the formulas in ...
992 views

### Modelling ISS orbit in GMAT

I am a complete newbie in all things space related. I am trying to work out how I can model the orbit of the ISS in the NASA open source tool GMAT. I can get the TLE for ISS (ZAYRA) from space-track....
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205 views

### 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?...
1 vote
261 views

### 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 ...
127 views

### 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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238 views

### 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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1 vote
105 views

### 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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438 views

### 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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1 vote
312 views

### 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 ...
721 views

### 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 ...
418 views

### 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 ...
234 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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474 views

### 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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275 views

### 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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577 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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1 vote
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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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215 views

### 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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1k views

### 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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1 vote
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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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### 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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