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.
97 questions
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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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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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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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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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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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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 ...
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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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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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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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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 ...
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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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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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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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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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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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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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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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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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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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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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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 ...
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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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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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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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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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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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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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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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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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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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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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GMAT ForceModel generated a derivative that is not a number
I'm simulating the orbit of an object multiple times and it works perfectly most of the time, but sometimes this error appears and I don't know how to fix it.
...
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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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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 ...
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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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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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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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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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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 ...
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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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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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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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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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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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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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A question about the improvement points for the simulation（GMAT)
Sorry for my English. I'm not a native speaker. I am using a software called GMAT from NASA to conduct various simulations, but I failed this time while trying to move a satellite from low Earth orbit ...
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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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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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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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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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