If I understand correctly, NORAD tracks thousands of satellites as well as pieces of space debris and publishes TLE files representing their orbital position and motion that are updated regularly. It must be a fantastic amount of work to keep these files up to date.

I love that they do this, and it's a great service to the community, but why?

Is it a legal obligation to make the data public? Is it out of generosity? habit?

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    $\begingroup$ "It must be a fantastic amount of work to keep these files up to date" Probably not. $\endgroup$ Commented Jun 2, 2020 at 16:31
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    $\begingroup$ Can you elaborate? How would keeping track of the orbital characteristics of 1000s of satellites and pieces of space debris not a lot of work? Or are you referring to the actual publishing of the files themselves, in which case yeah I assume that's automated $\endgroup$ Commented Jun 2, 2020 at 17:05
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    $\begingroup$ @MaxHartshorn I used to work at a place that helped track these. It's not a lot of work. Thanks to the wonder of computers. $\endgroup$ Commented Jun 3, 2020 at 3:13
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    $\begingroup$ @horse hair: Yeah, writing the program that reads the data from various radars &c, does some computations, and writes the files probably took a fair bit of programming. After that, you just make sure the power stays on :-) $\endgroup$
    – jamesqf
    Commented Jun 3, 2020 at 3:37
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    $\begingroup$ @jamesqf exactly, it's just an impulse and then the work it tapers off significantly, to the end of time $\endgroup$ Commented Jun 3, 2020 at 3:40

3 Answers 3


It's actually good for a few reasons. Providing the data to the satellite operators can help them to better know where they are, improving the usefulness of their services. Some of the communication satellites might be used as well to the military, with the easy to ingest format. They can spot potential problems that they might have otherwised missed, and in general this is of good use to the public.

It's worth noting that this is data that they collect anyways, and it isn't a lot of work to make it available to the general public. The military is collecting this data to find spy satellites from other countries, among other things. Given the huge use of this data to the public, and the relatively little work to make it public, it makes sense that they would make the data public.

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    $\begingroup$ The main reason that NORAD is collecting the data is to have a list of things coming over the horizon that aren't nuclear-missile attacks. $\endgroup$
    – Mark
    Commented Jun 3, 2020 at 2:34
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    $\begingroup$ Not just that, but that certainly is a factor. $\endgroup$
    – PearsonArtPhoto
    Commented Jun 3, 2020 at 2:36
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    $\begingroup$ Some work is needed to make those TLEs available to the public. The data have to be scrubbed for objects whose states are not intended for public release, as that public release includes release to countries that are not exactly the US's friends. I would presume that even countries that fall into the dearest friends category aren't privy to everything. $\endgroup$ Commented Jun 3, 2020 at 9:05
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    $\begingroup$ Russia and China almost certainly have somewhat equivalent capabilities. One problem with not disclosing some TLEs to the public is that the missing data tell Russia, etc., which objects the US military deems to be of great interest. $\endgroup$ Commented Jun 3, 2020 at 9:12
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    $\begingroup$ It would seem that filtering the data to classify it at different levels would need to be done anyway if sharing with satellite operators or even government bodies that aren't part of the national security operation $\endgroup$
    – Chris H
    Commented Jun 3, 2020 at 9:59

The two existing answers are great, but they do not mention that the reason this data was initially made available was due to a law passed by Congress back in 2003. This page, although it's very out of date now, does a good job explaining the beginning of it: https://celestrak.org/NORAD/elements/notice.php

The post begins:

As a result of legislation passed by the US Congress and signed into law on 2003 November 24 (Public Law 108-136, Section 913), Air Force Space Command (AFSPC) has embarked on a three-year pilot program to provide space surveillance data—including NORAD two-line element sets (TLEs)—to non-US government entities (NUGE). This service was to be established "not later than 180 days after the date of the enactment" of Section 913 or by 2004 May 22 (paragraph (i)). AFSPC officials have indicated that the NASA OIG web site—which is the source of CelesTrak's data—would be operated until 2004 October 1 (less than two months from today) to allow users to get the information necessary to plan their transition to this new data service. This transition time is extremely important because Public Law 108-136 prohibits the redistribution of the data obtained from this new NUGE service "without the express approval of the Secretary" [of Defense] (paragraph (d)(2)).

It continues and includes several updates that can be read there.

  • $\begingroup$ I would recommend removing feedback for the other answers, as this may get downvoted. $\endgroup$
    – WarpPrime
    Commented Jun 3, 2020 at 23:01

I would also like to add that although NORAD tracks all of these satellites and debris, they might not actually know which is what (particularly after separation of payloads from the launch vehicle).

Publishing TLEs for these unknown objects is particularly helpful to ground stations, allowing them to plan their scheduling while attempting to contact and identify newly launched satellites.

Take, for instance, this screen shot below from AGI's Systems Toolkit (STK) software that NASA IV&V engineers were using to help locate their newly launched cubesat STF-1 (which was among 12 other cubesats on the ELaNa XIX Launch).

Basically they picked an unknown object's TLE, tried to talk to it, and if it didn't answer they picked another one on the next go around. Once you find yours, you can essentially 'claim' it via Space-Track.org and submit the identification of the object.

enter image description here

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    $\begingroup$ Was going to comment to correct your STK abbreviation only to find that I have been away from the STK scene for too long, It used to stand for Satellite Toolkit, but it is indeed now Systems Toolkit, and I am certified in STK from AGI! $\endgroup$
    – Glen Yates
    Commented Jun 3, 2020 at 16:34
  • $\begingroup$ Yeah, and several spacecraft operators on that launch never did find their spacecraft. About half were found within the first few weeks, but as of middle of last year, there were still 5-6 unclaimed. This isn't unusual - and at least we know where they are. $\endgroup$
    – jimlux
    Commented Jun 3, 2020 at 17:15
  • $\begingroup$ And sometimes NORAD loses track. In 2002, HETE-2 ops got a message from NORAD that was essentially "can you tell us where your satellite is?" Objects in low altitude low inclination orbits aren't ever in sight of most of their assets. But we were tracking it with its onboard GPS, so we could tell them. $\endgroup$
    – John Doty
    Commented Jun 5, 2020 at 16:08

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