[ahubert]

Hi makomk, (author here)

Indeed, Galileo has nothing like this. The GPS solution sounds exceptionally fancy, and it may go a long way to explaining where all those billions of USD/year go :-) Do you know if it has ever been tried for real? Thanks!

[londons_explore]

Doesn't sound that fancy... Orbital calculations are hard maths, but when you've written code to do it, that code can run anywhere, including on the satellite. Very little compute power is required.

Also, satellites are in direct view of one another and can easily receive each others signals. A rather simple software radio could receive the signals from a basic omnidirectional antenna. The only challenge is subtracting out the very strong local signal before digitising, but considering the very strong coding gain in GPS, it should be doable.

[guenthert]

> A rather simple software radio

I'd think that would be rather a phase accurate software radio.

[londons_explore]

Aren't all software radios phase accurate...?

[makomk]

I'm not actually sure if it's been used for real, and I don't think it's really been needed - apparently it's rare for GPS ephemeris data uploads to be late by even an hour or two. In principle the idea is that it would be operating all the time and give slight accuracy and integrity monitoring improvements, but that doesn't seem to be a priority.

Incidentally, it seems like the EU is looking at developing their own version of Autonav for the next generation of Galileo, quite possibly with optical rather than radio links between the satellites.

[Aloha]

I mean the system was designed as a military tool, with the primary scenario of surviveability being nuclear war, so the level of redundancy seen makes sense to me.