Linked Questions

4
votes
3answers
442 views

Is the amount of accurate information in a TLE equal to that of a single state vector?

My question is basically regarding whether there is orbital information "lost" when converting from a Two Line Element set (TLE) to a state vector. Given that the following are true: I have a TLE, ...
7
votes
2answers
969 views

Is SGP4 propagation necessarily more accurate near the epoch chosen for TLE generation?

This interesting answer includes a quote from Space-Track: From Space-Track.Org FAQ TLEs can contain future epochs. About 20 satellites are categorized as "multi-day objects" because ...
2
votes
1answer
157 views

SGP4 on Systems Tool Kit (STK); how to check if SDP4 deep space correction is implemented?

I am doing orbit propagation for a geostationary satellite which requires the deep space corrections of SDP4. See my previous question SGP 4 for Geostationary Satellite. I am using SGP4 on STK, but, ...
4
votes
1answer
70 views

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 ...
2
votes
1answer
85 views

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 ...
1
vote
1answer
82 views

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 ...
15
votes
3answers
13k views

How can I plot a satellite's orbit in 3D from a TLE using Python and Skyfield?

I have obtained a Two Line Element (TLE) of a satellite in Earth orbit from Celestrak at https://www.celestrak.com/NORAD/elements/ and I would like to use it to calculate an orbit. How can I ...
8
votes
2answers
389 views

How to calculate the very special orbit of 2020 SO

From a NASA JPL page: Earth May Have Captured a 1960s-Era Rocket Booster Source (Sorry, I got an error when I tried to include an animated gif.) 2020 SO was captured by Earth's gravity on Nov. 8, ...
1
vote
0answers
209 views

Cis-L2 Libration Point Halo Orbit

Queqiao became the first satellite to orbit the Cis-L2 libration point (far side of the moon). Link: https://en.wikipedia.org/wiki/Chang%27e_4 Does anyone have any insight on how to model this orbit ...
4
votes
1answer
278 views

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 ...
1
vote
0answers
60 views

Confused about SGP4 implementation published by celestrack

I was trying to understand how SGP4 computes the propagated position I had a look on the original publication paper but i have not found a satisfactory answer. So I had a look to the Matlab ...
12
votes
3answers
1k views

Why are Tiangong-1's Apogee and Perigee Graphs Wobbly?

The apogee and perigee graph of the Tiangong-1 space station, about to re-enter and break up Real Soon Now, is depicted in this graph (source: Wikipedia): Why are the graphs wobbly? Is it because the ...
3
votes
1answer
385 views

How can Earth-Centered Inertial (ECI) coordinates be properly called "inertial" if the Earth's orbit is always accelerating towards the Sun?

I've just realized (again) that I don't understand anything, something that often happens to me after reading a @DavidHammen answer. How can Earth-Centered Inertial (ECI) coordinates be inertial if ...
4
votes
1answer
150 views

SGP 4 for Geostationary Satellite

I have read some sources that say that SGP4 is for satellite which have orbital period less than 225 minutes. For orbital period more than 225 minutes, we should use SDP4 instead. I need a ...
3
votes
2answers
194 views

When calculating the future orbit of an artificial Earth satellite, is the Moon's gravity significant or insignificant?

Imagine a mathematician is plotting the future orbit of a satellite to be launched and put in orbit around the Earth. When they are making their calculation, is the moon so far away and the ...
6
votes
1answer
264 views

Is TESS really lost? What does Celestrak mean exactly?

From this answer to the question What artificial satellite has the farthest orbit around the Earth?: I found the following "far out" spacecraft: TESS (Transiting Exoplanet Survey Satellite)...
3
votes
2answers
657 views

Has a TLE ever been issued for a spacecraft trajectory not bound to Earth orbit?

This excellent answer to the question Why has no TLE been published for the DSCOVR satellite and the Falcon 9 R/B? suggests that to the best of the writer's knowledge TLEs are only issued for ...
5
votes
1answer
1k views

Differences between SGP8 and the standard SGP4? Is it ever used in practice?

The Wikipedia article Two Line Element Set says: The SGP4 model was later extended with corrections for deep space objects, creating SDP4, which used the same TLE input data. Over the years a ...
1
vote
2answers
276 views

Can the deactivated satellites also be tracked through TLE?

TLE is used to track whether the satellites are in orbit or not. However, is it possible that a particular satellite is deactivated, decommissioned or deorbited yet its TLE is being updated regularly?
5
votes
2answers
728 views

Sun-synchronous satellite orbit propagation

I'm trying to propagate the orbit of a sun-synchronous satellite. The initial data is defined by the TLE. The orbit of the satellite is controlled by the operator ...
5
votes
1answer
2k views

TLE SGP4 Coordinate Transformations

I am working on developing a user friendly SGP4 orbit propagator in C on a PIC24. I have extensively read Revisiting Spacetrack Report #3 and celestrak - there are a few outstanding questions I have....
13
votes
4answers
14k views

How to obtain UTC of the epoch time in a satellite TLE (two line element)?

I want to convert the epoch time of a TLE to UTC. At this moment I am less interested in explanations and history - I just want to know quantitatively, with certainty, how to convert. I'm confused ...
5
votes
2answers
453 views

Why are Keplerian elements used in TLEs instead of Cartesian state vectors?

Propagating a state vector seems easier, you just account for the gravity, change the velocity and update the position. It also allows to easily apply perturbations, etc. Additionally, the ...