Comment by Symmetry
1 year ago
Right. The Iridium network had communication between satellites in different orbital planes passing each other but that was a pretty unusual capability.
1 year ago
Right. The Iridium network had communication between satellites in different orbital planes passing each other but that was a pretty unusual capability.
They do have counter rotating planes though, so there are places where two satellite tracks next to each other moving in opposite directions, and these pairs of satellites cannot use the cross plane communication mode.
Additionally, their inter satellite links use regular Ka band radio.
I wonder how iridium actually handles the tracking (or if it’s just slow enough and lack of attenuation in free space just lets them blast it).
And if they have zones where they don’t go to adjacent orbits, but instead go up or down within their orbit for the handover between orbits.
Supposedly they use steering, since the horizontal azimuth to adjacent-plane satellites varies from 0 to 65 degrees across an orbit: https://apps.dtic.mil/sti/tr/pdf/ADA348174.pdf
It doesn’t get into it too much on pages 14 and 15, but it indeed suggests that they probably exclusively use the “intra-orbital” links closer to the poles to get data to a satellite where the inter-orbital links are more practical.
I believe Iridium had way more downlinks than they used to pre-bankruptcy. I guess volume constraints were less of an issue, so ok to hop around more in space.
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