zlacker

>>alden5+(OP)
My understanding of the state of the art of inter-satellite optical links is that they have only been used between satellites that are basically in the same orbital plane and in more or less the same orbit. That is, the angle from one satellite to the other changes very very slowly, so that the optics don't have to do much tracking -- and consequently satellites can only form an optical link with other satellites that are ahead or behind themselves in ~ the same orbit.

Cross-plane optical links would have a trickier tracking problem.

While there's no explicit mention of same-plane vs cross-plane optical links, I assume that the first time people have a public cross-plane optical link, they will make a big deal out of it. :)

The article also mentions that SpaceX would need to do further study before using laser links between satellites and ground stations-- this kind of optical link would require both more angular tracking and probably atmospheric correction as well.

>>ble+c55
Right. The Iridium network had communication between satellites in different orbital planes passing each other but that was a pretty unusual capability.

>>Symmet+pb5
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.

>>Scound+Zd5
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

>>lxgr+CM5
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.

>>Scound+tV5
This has more details: https://fcc.report/IBFS/SAT-MOD-20131227-00148/1031348.pdf

Apparently it only happens above/below 68 degrees latitude, so the next satellite with a working inter-orbital-plane connection is at most one hop ahead or behind.

https://spaceflight101.com/spacecraft/iridium-next/ has some more photos and diagrams; seems like they're really mechanically steered even on the NEXT constellation.