# Questions tagged [two-line-elements]

Set of values carefully prepared to be used together with a simplified perturbations model (most often SGP4) to predict satellite positions with a moderate level of accuracy for times near the epoch contained within the TLE.

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### change epoch to ( epoch year and Juilan day fraction )

the question asks you to make two line element it give you the given information and also everything is answered but the one thing i don't understand in here is how do the change the Epoch 29 sep 2010 ...
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### TLE propagation, I don't understand which time should I use in (t - t_0)?

I'm trying to plot ground tracks with the help of TLE data. However, there are some equations that contain "times", and I can't understand which time I should use and format. Like for ...
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### PseudoTLE creation

I am developing a script in python to obtain pseudo TLEs of a satellite, starting from its state vector. I have always used TLEs to propagate the satellite and predict its next pass over a ground ...
719 views

### TEME state vector to TLE orbital elements

I was looking at time series of some TLE parameter(semimajor axis, inclination, etc..) and I wanted to how those parameters evolve between measured time points. So i decided to feed TLE element to ...
1 vote
222 views

### Distance between a satellite and an orbit

I would like to compute the distance between a satellite and a specified orbit. For instance, for an orbit at 897 km altitude, 0 degree eccentricity, 99 degree inclination, and RAAN of 0 degrees on ...
67 views

### TLE along track error to miss a contact opportunity in UHF

Update: (following @GregMiller's comment): Lets suppose a spacecraft has performed a boost and not all ground stations received the update, lets suppose the difference between the pre and post ...
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### How to make my generated two line elements more accurate?

I am using Orekit to generate TLEs. I am then propagating those elements out and comparing it to the ephemeris used to generate them. This results in a residual error in excess of 20 km. I am not ...
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### Retrieving TLE file when offline

How does one retrieve the TLE file without any internet access? For instance, I am out in the open sea without an internet connection for a few days. Can I still get the latest TLE file by some other ...
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1 vote
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### 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 ...
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### Plot ellipse using elements from TLE

I am trying to draw an ellipse as satellite orbit in three.js, It has an EllipseCurve class which takes these inputs and draws an ellipse around center. EllipseCurve( aX : Float, aY : Float, xRadius : ...
1 vote
357 views

### Is there a python library to determine the position of a satellite at a given time from TLE data excluding the Satellite catalog number?

Or perhaps some simple code or formula that achieves this. I've used pyephem but it requires a Satellite catalog number.
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1 vote
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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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526 views

### How to Update the Epoch in a Fake TLE While Maintaining Relative Position?

I've been trying to compare before & after results for some updated algorithms in an application. Basically, I want to be able to start and run the test at any arbitrary Epoch with the satellite ...
1 vote
1k views

### Are the TLE of a satellite computed with the ECI or ECEF?

I want to compute the distance of a certain satellite, given the TLE, to a ground station in the earth. I have the latitude, longitude and altitude of the ground station. But I don't know if the TLEs ...
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### 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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### satellite ground track calculation

I'm trying to calculate the ground track of an earth-orbiting satellite (Longitude, latitude) I found this handy way on the documentation but it's good when trying to find a single point what if I'm ...
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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 ...
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1 vote
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### 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 ...
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### How do I know the exact TLE of my satellite after its deployment?

The satellites are launched in a cluster. How can I validate the TLE of my satellite in the early days following deployment, because there are more than two satellites that are close to each other and ...
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### Why can n2yo somehow interpret this TLE but Skyfield can't? Why does it return nans and zeros for position?

@Rafa pointed out that there is at least one officially released TLE for the JWST mission after it left Earth orbit, and here's the latest one at n2yo.com: ...
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### Does the James Webb Space Telescope have a Two Line Element set?

How do you track the position of the James Webb space telescope? Does it have its own TLE, or...?
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 ...
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### Failing at getting apogee and perigee from TLE

At Celestrak, the current orbit for ISS is currently listed as 423x417 km, but if I'm getting the TLE data from Celestrak and use orb.get_lonlatalt(now) from ...
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### Suppose I wanted to compare TLEs to actual LEO satellite positions, what data is available? From which may it be easiest to extract X, Y, Z, T points?

Under @RyanC's answer to How can I plot satellite's trajectory from three different TLEs to detect any deviation on path with time? I wrote: I think that SGP4 + TLEs is so popular because the TLEs ...
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1 vote
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### Given the measured positions of an object, how to retrieve its latest TLE?

I'm working on a simulation space project, in which I simulate the positions of all the Low Earth Orbit objects at any time. For the moment I have a 3LE database of LEO objects, and each time a ground ...
365 views

### Calculating Which Satellite Passes are Visible - Need help

I am a beginner Python programmer. I am trying to get the code in the article "Calculating which satellites are visible" to function without success. My plan is to identify satellites that ...
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### Is there an API for accessing old TLEs of non-historic objects?

There are various APIs online for accessing TLEs for a satellite object from CelesTrak. However, the APIs retrieved are usually the most recent ones generated. There are also a lesser number of APIs ...
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### How to generate TLEs based on a set of observation points (location, azimuth, elevation... no range)

I'm interested in generating a "corrected TLE1" based on observation data. I would have observed azimuth and elevation, site location, and time. All of those data fields are observed with ...
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### Textbook or scholarly discussion of equations used by the SDP4 part of SGP4 TLE propagators beyond Space Track Report #1?

(the famous) Space Tract Report #3 discussed at length in Dr. T.S. Kelso's Revisiting Spacetrack Report #3, AIAA 2006-6753 Describes the "deep space" corrections to the original SGP4 known ...
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1 vote
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### Did Tianzhou-2 have a TLE before docking with Tianhe 8 hours after launch? Which is the 2nd stage rocket body and roughly how soon will it reenter?

Clicking on https://celestrak.org/NORAD/elements/stations.txt I get ...
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### Where can i find ELSETS with Co-Variances?

For Special Permutations (I'm a novice), an ELSET with covariance is more accurate than without covariance. A TLE doesn't have room for any covariance. However, I can't seem to find a catalog that ...
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### 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?

@BillGray's answer to Why can't custom-made TLEs for the DSCOVR launch booster in orbit around Earth work with SDP4? is quite interesting and informative; I fail to do it justice by summarizing it as ...
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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 ...
783 views

### How do cubesat owners first find out their cubesat's initial trajectory? How do they point antennas at it before official TLEs start to appear?

When cubesats are first deployed it can sometimes take several days before they start appearing in official TLE distributions, and even then if many were deployed it may take a lot more work to decide ...
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### What is the "+" symbol for the drag term encoded in a TLE?

I have two TLE, the drag term for the first TLE is -26868-1, which I suppose equals to -0.026868. But on the second TLE, we have ...
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### Tutorial for orbits from TLE data

I've been looking for a new hobby, and have been reading some about satellite tracking. I was wondering if there was a good tutorial that walks through how to use TLE data. So far I have found ...
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### 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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### TLE filtering techniques to remove the mean motion/eccentricity/inclination outliers

I am working on a TLE filtering code to prepare the TLE series for orbit propagation. I am using a sliding window approach with meadian+ n*mad or IQR to detect the outliers in those orbital elements ...
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### TLE on path to be deprecated - what is 9 digit?

The TLE format will soon run out of numbers. The US Space Force is implementing an Alpha 5 scheme where the first byte of the NORAD_ID will be a letter giving nearly 400,000 numbers. After that a 9-...
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### Will the new "TLE format" be orbitally-mechanically better than traditional TLEs?

Celetrak's A New Way to Obtain GP Data (aka TLEs) by Dr. T.S. Kelso 2020 May 27 explains the arrival a new infoblob format that in several ways is "better" than the ancient TLE, and contains ...
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### Why can't custom-made TLEs for the DSCOVR launch booster in orbit around Earth work with SDP4?

This fascinating answer to Why has no TLE been published for the DSCOVR satellite and the Falcon 9 R/B? presents links to custom-made TLEs for the Falcon 9 rocket body that put DSCOVR into orbit, and ...
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### Get dates when a satellite has performed maneuver from historical TLE data (python)?

I have been recently acquainted with orbital mechanics and am trying to do some analysis on the subject. Since I don't have subject matter expertise, I am at a crossroads with trying to decide that ...
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### Second derivative of mean motion as indicator of deorbit

I noticed that the second derivative of mean motion (SDMM) is non-zero for only a small percentage of the NORAD catalog. All those objects I checked have reentered since the TLEs I was using were ...
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### Where can I find a satellite/space debris database with object masses

The title pretty much says it all. As far as I can tell the default method by which space debris objects are tracked/stored in a database is using two line element sets. However these have no way to ...
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### How can I plot satellite's trajectory from three different TLEs to detect any deviation on path with time?

I have obtained TLE information of a satellite from space-track.org for three different times. I am trying to study any deviation of the satellite trajectory from its usual path. Here I am comparing ...
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### How do two-line element sets handle rev numbers > 99,999?

In a two-line element set (TLE), five characters in line 2 -- columns 64-68 -- are for the rev number. (https://en.wikipedia.org/wiki/Two-line_element_set) But some satellites have been around the ...
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### How can I plot a satellite TLE from its orbital parameters using python and skyfield? [closed]

I have a function that uses TLEs (Two-line elements) from Celestrak to plot the visibility of a satellite in Python. Is there a method with skyfield or poliastro to plot a TLE from given orbital ...
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