3
$\begingroup$

I don't understand how we can get an uninterrupted line of sight with geostationary satellites with the presence of a high number of polar satellites in Earth's orbit. When microwave signals are used between GEO satellites and any base station, we must have a line of sight to convey information across, so isn't there a chance that this signal will be blocked by polar satellites as they occult geostationary satellites?

$\endgroup$
  • 1
    $\begingroup$ You mean that passing polar satellites would block the line of sight to the geostationary satellites? $\endgroup$ – Rikki-Tikki-Tavi Oct 23 '14 at 10:59
  • 2
    $\begingroup$ Welcome to Space Exploration! Please edit your question so that it is more clear what you are asking. Do you mean line of sight for radio communications? $\endgroup$ – Stu Oct 23 '14 at 13:01
  • $\begingroup$ Since GEO satellites have a much larger foot print . I imagine It wouldn't be noticed especially since the LEO are lower orbits and move a helluva a lot faster. $\endgroup$ – Old_Fossil May 25 '16 at 3:15
14
$\begingroup$

Satellites in LEO travel at around 7000 m/s. This means that a 1 m sized LEO satellite will take around 150 us (microseconds) to cross a given line between a GEO satellite and a ground antenna.

So it is a very short event, and all satellite communications are protected against error bursts (especially from interference) by using FEC (forward error correction codes) and other diversity methods.

Moreover, a LEO satellite crossing a particular GEO-to-ground line is very improbable (many LEO sats, but an extremely large area around Earth to "hold" them).

So my guess is that these events are less probable and less important than other sources of interference and attenuation that satellite communications are exposed to normally (like sun radiation, clouds and rain, ground based interference, aeroplanes).

P.S. For a finer calculation, note that to effectively block a radio link, you would have to cover much of the section of the first Fresnel zone; it's not just crossing the imaginary line between satellite and receiver.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.