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I am looking for true real-time satellite tracking data. I know it can be calculated but that is not true real time tracking - or it does not seem to be when using TLEs.

What I am looking for is the information about where a satellite is not where it is supposed to be.

Does anyone know where or how to get such information?

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    $\begingroup$ I do not quite understand what the problem is with TLE? These recent data allow us to calculate quite accurately the position of the satellite in the sky. amsat-uk.org/beginners/satellite-tracking $\endgroup$ – A. Rumlin Jan 11 '20 at 18:18
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    $\begingroup$ Locating satelites requires either pretty complex radar or clever processing of telescope data (because they do not directly get range). As such it is generally something you buy access to. $\endgroup$ – GremlinWranger Jan 11 '20 at 23:39
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    $\begingroup$ So let's examine what a "measurement" of a position of an object moving at almost 8,000 meters per second actually means. If the satellite has on-board GPS and is lucky enough to determine correlations for 4 signals simultaneously and do the conversion in 10 milliseconds, the satellite moves 80 meters during that time. The calculation in spaceflight-rated GPS systems include a model for at least linear motion within the time of conversion, so even conversion calculates where the spacecraft should be. $\endgroup$ – uhoh Jan 12 '20 at 0:35
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    $\begingroup$ That aside for the moment, any satellite that has GPS and is sending it live to Earth will report its position in near-real time. Of course by the time the data gets to your computer it's going to be hundreds of milliseconds old unless it's overhead and you're receiving it with your own antenna, and so it will still be wrong (or at least old) by a kilometer or so. But if you are asking about tracking satellites from the ground, they don't measure positions as much as they get several sets of incomplete data and then later calculate an orbit that fits those sets. It's always predictions $\endgroup$ – uhoh Jan 12 '20 at 0:39
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    $\begingroup$ @DaveGordon I think I understand your distinction, and so I think that the answer is generally no. It's a pretty good vacuum up there and the gravitational fields are known with great precision, so in general people will use predictions because except for extreme or unusual situations or very low altitude, satellite trajectories are surprisingly predictable. $\endgroup$ – uhoh Jan 12 '20 at 13:47
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In general, no. You can buy this data or build your own radio interferometer...

But in one particular case, you can find out where the satellite is in real time.

In the case of the Iridium satellite.

enter image description here enter image description here

To do this, you need:

  • Active L-Band 1525-1637 Patch Antenna

  • SDRPlay receiver

  • Iridium Toolkit

  • Clear sky overhead

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  • $\begingroup$ how incredibly cool! are the satellites transmitting actual, measured coordinates from their GPS receivers, or are they in fact just broadcasting data from some on-board ephemeris table they use for electronic steering of their communications beams? $\endgroup$ – uhoh Jan 13 '20 at 3:15
  • $\begingroup$ The STL system transmits signals through Iridium’s satellite constellation to deliver a unique code to each position on the ground that can be independently authenticated. reuters.com/article/us-iridium-gps-idUSKCN0YE1HZ $\endgroup$ – A. Rumlin Jan 13 '20 at 5:10
  • $\begingroup$ So are the coordinates derived from GPS on the satellites, or are they really a prediction from an ephemeris? This matters because it's the main point of the question. $\endgroup$ – uhoh Jan 13 '20 at 12:20

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