Questions tagged [propagation]

This tag is used for questions related to the prediction of objects in orbit, or in the prediction of evolutions of orbits, using various orbital-mechanic models such as: "two-body", NORAD's SGP4/SDP4, ... and /or numerical integration algorithms.

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114 views

Integration of Varying Forces, Impulses in Simulators

I am a software dude working on a personal project for building a spacecraft simulation software. And I've been looking into numerical integration methods, and I am just confused on how to tackle the ...
230 views

Orbit Determination from Position and Velocity

I'm working on a game, somewhat similar to KSP (no building rockets, just beautiful orbital acrobatics). It's in a "small" star system, radius of 6 AU, and it features celestial bodies ...
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80 views

ECI position and velocity from angular velocity

I need help with an orbital mechanics issue that I cannot figure out. I have the initial ECI position and velocity ($r_{vec},v_{vec}$) of a certain satellite. Through them, the angular velocity, the ...
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55 views

Reducing degree of ICGEM's Gravity Field Models for orbit propagation

I would like to use one of the static gravity field models published at ICGEM for satellite orbit propagation. For example, EGM2008. Its degree is 2190. I would like to use only 360 (may be even less) ...
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1 vote
95 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: ...
• 101
77 views

Difference between different numerical propagators

As a school project, I'm trying to model the evolution of a space-debris population orbiting around Earth. By doing researches, I found several numerical propagators. Though, I couldn't find any ...
370 views

Implemented analytical orbit propagator

Anybody knows about reliable open source implementation of analytical orbit propagator (for a generic orbit, given the initial state and not TLE)? Possibly including up to J2 and drag also. I have ...
294 views

Draper Semianalytical Satellite Theory (DSST) C/C++ version

Anyone knows where one could find the Draper Semianalytical Satellite Theory (DSST) semi-analytical propagator code in C/C++? I know Orekit includes the Java version inside its code. An in general if ...
1 vote
378 views

What would the TLE data (Mean Motion, Eccentricity, Inclination, RAAN, Argument of Pericenter) of GEO and PO be like?

I am currently making a satellite tracker app for android. I want to test my orbit propagation algorithm and I want to make some made-up basic orbits, so I need to know how their TLE would be. I want ...
• 11
695 views

Are J2 and J4 cases of EGM2008 and other spherical harmonics models?

EGM84, EGM96, EGM2008... are Earth gravity models that contain coefficients "up to" a number of degrees. When using GMAT, STK, MATLAB Aerospace, this parameter is the "spherical ...
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121 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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1 vote
295 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 ...
1 vote
157 views

Issue with propagating TLE sets using SGP4

I am trying to make some analysis on conjunction events using the TLEs available from Celestrak's SOCRATES page. Take for example the following predicted event: Here's my issue: when I try to ...
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651 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 ...
393 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 ...
1 vote
39 views

Is DTM2000 density model expecting adjusted or observed solar flux?

I know two models to calculate the atmosphere density during a satellite orbit propagation. The two models are NRLMSISE-00 and DTM-2000. To feed the models I'm using Space Weather Data provided by ...
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890 views

How to propagate the orbit of a satellite analytically using Lagrange planetary equations/VOPs and compare them with numerically propagated solution?

I have propagated the orbit of a satellite from TLE elements numerically using RK4 method. But I'm bit confused when it comes to the propagation of satellite orbits using analytical approach. From ...
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169 views

The video below Space debris over Puerto Rico (2/7/2022) SAC seems likely to show one or more reentering Starlink satellites from the 40 "Starlost" lost to atmospheric heating due to a ...
• 149k
1 vote
39 views

satellite orbit propagation from initial position and velocity [duplicate]

I'm trying to get the satellite orbit at a certain time given the initial position and velocity (SGP4) say I have a TLE file that is taken in epoch:(2022-01-05 11:25:15.578) and I need to get the ...
• 63
419 views

How is an input card for SGP4/other astro standards packages crafted?

I've read through the SGP4 documentation at least 5 times, and I swear the only reference it makes to the construction of an input card is "just look at the examples". For Sgp4Prop, it ...
962 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
1k views

calculating satellite position and velocity from TLE

I'm trying to calculate satellite orbit from the TLE set at first, I used several libraries including SGP4, Skyfiled to get the initial position and velocity of the satellite at the epoch time I know ...
• 63
314 views

Modeling satellite attitude for propagation of orbit

I recently obtained good results with a high-precision numerical orbital propagator using a constant effective area for drag and radiation pressure. I have now become interested in checking if the ...
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234 views

Wrong position during orbit propagation in Unity

I've been working on an orbital physics module for months now, and have reached a barrier. I have two methods, one to convert from Kepler elements to planet-centric coordinates, and the other to ...
1 vote
153 views

Another look at orbits of near-Earth satellites. What is wrong in this interpretation?

In a cartesian reference frame (O,X,Y,Z), put two circles centered at the origin O, of radius a. The blue circle is perpendicular to Z. The red circle makes an angle i with the blue (cf. Fig below). ...
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568 views

For any state vector of a satellite at an arbitrary time T1, is there another state vector at a given time T2 that will result in the same orbit?

I recently found the question In a 3D space defined by semimajor axis, eccentricity and inclination, what would be the shape of the space where SDP4 works better than SGP4? and have become interested ...
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1k views

Obtaining position of GPS and GLONASS satellites from RINEX navigation files

I am currently trying to understand the best way to use the available information in RINEX navigation files for GPS and GLONASS satellites. My main goal currently is to calculate the position at epoch ...
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498 views

Setting up orbit propagation in Orekit

Please forgive my ignorance, I'm new to orbital dynamics. I am using Orekit [https://www.orekit.org/] for orbital propagation in order to determine rise and set times for a MEO satellite, and am ...
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941 views

What is/was legacy TLE ephemeris type 2? (TLE, line 1, column 63)

Wikipedia's Two-Line Element Set entry for line 1, column 63 (1.12) says: Ephemeris type (internal use only - always zero in distributed TLE data)13 13Celestrak Frequently Asked Questions: Two-Line ...
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2k views

Accuracy of converting from TLE/Orbital Elements to Cartesian if used for other propagator?

Say that I wanted to propagate a real-life satellite based on an initial position in space. However, the only source of data I can get is from a tracking website like CelesTrak or Space-Track, where ...
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