From the answers to What is the name of the 'register' that keeps track of all the satellites? we can see that there are more than three 'registers' of artificial satellites - starting with:

Now imagine you have a list of satellites, and it tells you one of them should be roughly 'there' (in a particular orbit and position) above the Earth. How would you go about making sure it was 'there'? (And what are the implications if it is not 'there'?)

My question is: What is the process to verify the orbit of a satellite in a list of artificial earth satellites?

  • $\begingroup$ Orbiting objects are tracker using radar installations on ground. Apart of mapping/tracking orbital debris the system is also likely used to confirm the orbits of artificial satellites. Haven't got sources/time right now so no detailed answer. $\endgroup$
    – GittingGud
    Jul 26, 2019 at 9:29

2 Answers 2


Referring to your comment to uhoh's answer, in order to get from orbital information to real-world information there are multiple pieces of information you need. First you need to understand that SGP4 will take the TLE and give ephemeral predictions in an inertial frame.

This is great if you want to track objects in outer space, but very difficult to track from Earth. As a result, you would want to convert your trajectory data into an earth-fixed frame (ECEF) and there are a multitude of packages to do that depending on what you are using (javascript, python, java, etc.) and once you get your earth-fixed coordinates as a function of time, you can get your lat/long fairly easily from that.

Obviously there is more logic to answer your particular question underneath uhoh's question, but referring to your problem on getting to that logic is more within the scope of your question, I believe.


Now imagine you have a list of satellites, and it tells you one of them should be roughly 'there' (in a particular orbit and position) above the Earth.

Those lists of satellites definitely won't tell you anything about the position within the orbit, or much about the orbit at all. Have a second look at those lists.

For this question you need Two Line Element Sets or TLEs for each satellite that you would like to check to see where it is and if and when it might pass over a certain location at a certain time. You can get them in Celestrak. You can read more here. TLEs are interpreted by some computer program running SGP4.

Another option would be to use an online service such as N2YO or in-the-sky.org and I am sure there are others.

  • $\begingroup$ Thanks for this @uhoh - I get that the TLE is the encoding format and contains values representing the positions and orbital information. How do I get from "orbital information" to "will I see it if I look at 10.03pm on Jan 23rd at 45 degrees from vertical looking at N23E standing in Arizona?" $\endgroup$
    – hawkeye
    Jul 26, 2019 at 12:42
  • $\begingroup$ @hawkeye "TLEs are interpreted by some computer program running SGP4." You either find one of those programs that does it (I use Skyfield and Python) or find a website. There are several questions and answers in this site that cover it, have a look around and see which one seems to match your situation the best. $\endgroup$
    – uhoh
    Jul 26, 2019 at 15:10

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