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Maybe some people urge this is a DIY site question but i thought here is the proper place to ask this question.

Is it possible for amateurs like students with commercial and available equipment like RTL-SDR or other low cost things to determine the orbit of a satellite(to a reasonable accuracy). I'm not into orbit determination for all satellites but are there satellite that because of their specification or transmitting signals we can try out orbit determination algorithms. Are there any amateur teams practicing this?

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  • $\begingroup$ I assume you're familiar with TLE files (which are computed by experts, so don't really answer your question, but are useful). In theory, if you have 3 observations of the same satellite and assume an elliptical orbit, you should be able to work out the orbit parameters. Of course, part of the problem is identifying the "same" satellite if it drifts in and out of visibility. $\endgroup$ – barrycarter Oct 21 '18 at 18:06
  • $\begingroup$ LTE data actually are result of processing raw data, what i want is a reachable source for raw data to determine orbit of known satellites. $\endgroup$ – yekanchi Oct 21 '18 at 20:06
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    $\begingroup$ Possible duplicate of How are military satellites with (apparently) classified TLEs still showing up on sat map websites? -- Some useful information might be found in this answer $\endgroup$ – JCRM Oct 22 '18 at 0:42
  • $\begingroup$ If Kepler could pull it off in 1620, so can you! $\endgroup$ – Roger Dec 11 '18 at 15:11
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Yes it absolutely is!

I'm writing this to make this clear that your question is squarely on-topic.

Here is an example of a (very experienced) amateur, Scott Tilley, both finding and determining the orbit of a satellite, using (very nice) amateur equipment, (very nice) amateur software, and of course a software defined radio or SDR.

You can see from images there that the Doppler shift versus time, determined from SDR data could be matched to an orbit using a software package which I believe is available to the public (let's wait for more answers on this, I'm not an expert).

There are several challenges of course:

Reception

A small, low gain antenna plugged in to a USB SDR with no low noise amplifier (LNA) is not likely to get you anything useful for most satellites even in LEO. You'll need some combination of

  1. a really good amplifier,
  2. a small dish or Yagi antenna
  3. some luck and some patience waiting for the right satellite to pass, which is transmitting in the frequency chunk you happen to be receiving at that moment.

It's even possible you can do this with any two of the three.

And once you've got the hang of it in terms of observing times and frequency band to look, all you'll need is the really good LNA for at least some satellites.

Orbit Determination

As pointed out in comments above, lots of people track satellites, there are web pages about it and software packages out there as well.

Having an extended recording of frequency (Doppler shift of the unknown carrier frequency) versus time, software would start reverse-engineering the orbit that would produce this curve. It won't be unique, you won't nail the exact orbit with one pass, but you can narrow it down a lot, and with that predict possible times for its next pass.

If you don't have a directional antenna to get an approximate fix on some look angles, this is really going to be quite hard, so I think simply detecting the satellite will be a major achievement.

The images below is from some really fancy software that (I believe) includes using all kinds of available data on existing satellites (including the spy varieties) to help identify the spacecraft who's orbit matches. What you are asking about is orbit determination and I'm sure that software is available as well.

Happy hunting!


below x3: SDR and orbit analysis of the recently amateur-re-acquired IMAGE satellite. From NASA’s Long Dead ‘IMAGE’ Satellite is Alive!

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Here's amateur listener Sven Grahn watching the launch of Chang'e-1 and boost to deep space in 2007, from Tracking Chang’E-1 from Sweden

The map in the last one certainly doesn't look like Stockholm, but at that point in time Chang'e-1 is already in deep space so as long as it's in the listener's hemisphere it will be above the horizon.

The author also tracks a probe at the Moon in Finally picking up Selene in Stockholm

More fun reading at: How I caught "The Space Bug" and somehow started tracking satellites by radio

Pretty darn amazing work!

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    $\begingroup$ most of them are great at their work like Scott Tilley but what i found lacking is some tutorial and motivating cheap road-map to start tracking at least famous orbiting objects like iss and then calculating orbital element. of course it may be some far expectation of me comparing it with tutorials from software and computer science on the internet. $\endgroup$ – yekanchi Dec 11 '18 at 6:16
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    $\begingroup$ @yekanchi I see, so it's not so much "is it possible...?" but really "how can I...?"In that case, I'd recommend a second question "Now that I have found out it's possible, what would be one of the easiest satellites to hear, given an SDR radio, xxxx..." explain what you have in terms of front ends, highest frequency, if you want to build a simple antenna or buy one, etc. I am not sure if this site or Ham SE is the best place though. $\endgroup$ – uhoh Dec 11 '18 at 6:21

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