Questions tagged [sgp4]

The U.S. Space Force's Simplified General Perturbations software, version 4, must be used to correctly interpret the orbit data format known as TLE (Two-Line Elements).

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What is the rationale behind NORAD's use of TEME?

The most popular catalog of Earth-orbiting objects is NORAD’s. The catalog provides the so-called « two-line elements » (TLE) which essentially are computed orbital parameters of a catalogued object, ...
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SGP4: the accumulation of error in radial, in-track and cross-track

I'm propagating the trajectories of 2 LEO satellites (altitude 700 km) in 7 days and calculating the radial, in-track and cross-track distances to determine the risk of collision. JSPoC states that ...
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TLE/SGP4 state vector accuracy assessment

I’m using the Planet Labs state vectors downloadable from http://ephemerides.planet-labs.com/planet.states or http://ephemerides.planet-labs.com/planet_YYYYMMDD.states to assess the TLEs/SGP4 accuracy ...
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Why did the Chinese put the Tiangong-2 so high?

The most obvious answer is that they don’t want to deorbit the station shortly, but why? Some calculations with the TLEs and SGP4 show the following Tiangong-2 / ISS close encounters: ...
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How to calculate a satellite LTAN on the basis of Cartesian coordinates in GCRS frame?

I have calculated the Cartesian coordinates of a satellite in GCRS frame using Skyfield package in python. Propagating the sun-synchronius orbit, I want to analyse the change in its LTAN. How could I ...
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How to use David Vallado's AstroLib to do reference frame conversions

Given a Keplerian Orbit description such as that in here: ...
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Understanding the paper "Determination of Satellite Orbital Elements by Means of On-Board GPS Receiver and Its Verification" by Yoshiwo Okamoto et. al

I have been assigned with implementing the algorithm proposed in the paper "Determination of Satellite Orbital Elements by Means of On-Board GPS Receiver and Its Verification" by Yoshiwo ...
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Satellite tracking telescope integrated program in Matlab

How can I get a comprehensive, integrated MATLAB program to set up and capture SGP4 output for telescope mounting? I am currently receiving state vectors from the SGP4 program, which include the ...
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How does the Gpredict software algorithm track satellites?

I was wondering how Gpredict calculates the ground tracks, Lat, Long and elevation based on a ground station. If I understand correctly, Gpredict takes the values from a TLE (Two-Line Element) set, ...
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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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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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Calculating t(E)

The mean radius vector of an elliptic orbit is equivalent to the semi-major axis. If I sample the radius vector of an unperturbed elliptic orbit as a function of the eccentric anomaly with at a ...
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Conversion of osculating orbital elements to TLE mean elements

I am looking for a method to resample TLE data, so they are regularly sampled. I wanted to use physical propagation to calculate elements at given time. However, the propagation of TLE by SGP4 returns ...
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TEME to J2000 conversion algorithm

I've asked a few questions to do with this in the last day or so and received answers that have led to more questions... How to use David Vallado's AstroLib to do reference frame conversions https:...
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Is Vallado's Revisiting Spacetrack Report #3 still relevant today?

The title pretty much sums it up. I am reading David A. Vallado's Revisiting Spacetrack Report #3, which was published in 2006 and includes source code for the SGP model series. I was wondering, is ...
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