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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1answer
64 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, ...
4
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2answers
130 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 ...
2
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1answer
40 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 ...
3
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0answers
61 views

How the B-Plane parameters are generally determined

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. ...
4
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2answers
84 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 ...
3
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2answers
137 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 ...
5
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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 ...
1
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1answer
133 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. ...
5
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0answers
80 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" ...
2
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0answers
72 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 ...
3
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1answer
137 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 ...
2
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0answers
166 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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0answers
112 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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0answers
132 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? ...
4
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1answer
259 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 ...
3
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1answer
742 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! ...
5
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1answer
270 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 ...
2
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2answers
434 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 ...
3
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1answer
130 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 ...
4
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1answer
586 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 ...
5
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1answer
875 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 ...