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.
125 questions
2 votes
1 answer
102 views
Why do some NORAD TLEs have an 8-char eccentricity field?
Recently some TLEs from NORAD have become incompatible with sgp4 propagators. Particularly, in this page I can find the following couple of TLEs: ...
- 655
3 votes
1 answer
128 views
History, usage, and redundancy(?) of the three "draggy" TLE parameters that can lower orbits?
After writing two answers, then having second thoughts, then reading Revisiting Spacetrack Report #3: Rev 3 I've decided that I don't know anything. The first line of a TLE has three parameters that ...
user12102
3 votes
1 answer
177 views
At which altitude is B* neglectable?
Obviously, B* is an arbitrary number only used as a crutch for orbital propagators, but I was wondering for which orbits is it useful or starting with which altitude it can be neglected? In terms of ...
- 143
4 votes
2 answers
371 views
Is the mean motion measured for the generation of TLEs?
I know that before generating TLEs with SGP4, there has to be a measurement of some points. What exactly gets measured in these points? Is it the mean motion or the semimajor axis? How is the ...
- 143
3 votes
1 answer
271 views
How to use the B star term present in a Two Line Element data for extracting Ballistic Coefficient of a spacecraft?
I'm writing a Python script to calculate the effect of atmospheric drag on a spacecraft in LEO by evaluating the change in the square root of the semi-major axis over time. The governing equation I'm ...
4 votes
1 answer
2k views
Where are the Kuipers? Has anyone seen one yet?
CNN's April 28, 2025 Amazon launches Project Kuiper satellites designed to compete with Elon Musk’s SpaceX says: Twenty-seven satellite took flight atop an Atlas V rocket, built by United Launch ...
user12102
2 votes
0 answers
134 views
Calculation of TLE like mean elements from state vectors
I have state vectors describing the satellite’s orbit under the influence of moon, sun, radiation, and the spherical Earth with zonal and tesseral terms. I want to generate a time series of mean ...
1 vote
1 answer
162 views
Weird single point anomalies in TLE data eccentricity parameter
When looking at the TLE data, I noticed weird anomalies in eccentricity for some satellites. These anomalies consist only of single data point, and data before and after them do not change trend. When ...
1 vote
1 answer
242 views
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 ...
- 21
2 votes
1 answer
123 views
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 ...
- 103
3 votes
2 answers
569 views
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 ...
- 31
4 votes
1 answer
2k 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
1 answer
363 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 ...
- 113
3 votes
1 answer
121 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 ...
- 63
2 votes
1 answer
467 views
Get fully defined orbit from space-track.org SATCAT
My question is related to this one on Physics SE. Admittedly, I'm somewhat preempting the answer over there being "you can't, there's a missing parameter", so if it comes back that you can ...
- 573