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The July Galileo Outage: What happened and why

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Re: The July Galileo Outage: What happened and why

#51

Post by blub »

FeepingCreature wrote: post #42

My current impression from reading this article is that SpaceX could create a better GNSS than Galileo in a year as a side project - not because of their cheap launches, but because of their diy development culture. I am stunned by the level of organizational inadequacy of allowing such critical parts of the system to be developed by not just a contractor but a chain of subsidiary contractors, with feedback cycles th…

I think you're being downvoted because you made a pretty amateurish mistake: on HN you're supposed to say that you yourself can create a better GNSS over the week-end.

Re: The July Galileo Outage: What happened and why

#52

Post by londons_explore »

toomuchtodo wrote: post #17
makomk wrote: post #12

Earlier quoted context omitted.

The 60 day long-term ephemerides were the older sytem. Autonav on the current GPS satellites is considerably fancier - basically, the satellites carry out ranging measurements between each other and compute their own updated clock and ephemeris solutions on the satellites themselves in a distributed fashion. Specced to provide essentially full accuracy for something like six months, minus ionosphere estimates which c…

Any chance we'll see WAAS reference stations with more autonomy for uploading ionsphere correction data directly to the constellation, instead of having to aggregate at master stations, which then forwards to ground uplinks?

Why would you want that? For slightly more accuracy in a severe ground station outage?

Seems only marginally worth it...

Re: The July Galileo Outage: What happened and why

#53

Post by londons_explore »

ahubert wrote: post #50
makomk wrote: post #12

Earlier quoted context omitted.

The 60 day long-term ephemerides were the older sytem. Autonav on the current GPS satellites is considerably fancier - basically, the satellites carry out ranging measurements between each other and compute their own updated clock and ephemeris solutions on the satellites themselves in a distributed fashion. Specced to provide essentially full accuracy for something like six months, minus ionosphere estimates which c…

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!

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.

Re: The July Galileo Outage: What happened and why

#54

Post by abdulhaq »

FeepingCreature wrote: post #42

My current impression from reading this article is that SpaceX could create a better GNSS than Galileo in a year as a side project - not because of their cheap launches, but because of their diy development culture. I am stunned by the level of organizational inadequacy of allowing such critical parts of the system to be developed by not just a contractor but a chain of subsidiary contractors, with feedback cycles th…

Galileo is a strategic asset in case of dispute with the US. It is not in a competition with GPS, it simply has to function as designed and continue to operate independently of US desires. The US objected to the construction of the Galileo system.

Re: The July Galileo Outage: What happened and why

#55

Post by zmk_ »

ahubert wrote: post #47
guykk22 wrote: post #41

Just wanted to give you a little bit more info. I work for the Spanish company that has developed the OSPF, GMV, and although I'm not currently involved at all in this project, from what i know, the following statement: "around 5% of the Galileo capacity is lost to software problems likely in the Orbit Synchronization Processing Facility (OSPF), run by GMV." is not fully true. The OSPF receives data from sources (Fro…

Hi - thanks for this (author here). What I mean is, currently, around 5% of the satellites on average broadcast NAPA status. I did not refer to the big outage with this statement, I mean to ongoing developments. Or perhaps you are referring to the same thing & in that case it is entirely possible that the NAPA flag gets raised because the ephemeris is being generated from stale data. Do you know? Thanks!

So that's 1 satellite on average. Even though 5% means the same it makes you think the number is much larger if you do not constantly think of the total available.

Re: The July Galileo Outage: What happened and why

#56

Post by creato »

abdulhaq wrote: post #54
FeepingCreature wrote: post #42

My current impression from reading this article is that SpaceX could create a better GNSS than Galileo in a year as a side project - not because of their cheap launches, but because of their diy development culture. I am stunned by the level of organizational inadequacy of allowing such critical parts of the system to be developed by not just a contractor but a chain of subsidiary contractors, with feedback cycles th…

Galileo is a strategic asset in case of dispute with the US. It is not in a competition with GPS, it simply has to function as designed and continue to operate independently of US desires. The US objected to the construction of the Galileo system.

The US did not object to the concept of Galileo, the US objected to the EU's choice of frequency, which made it impossible to jam Galileo without jamming GPS. The EU changed the design to avoid this, and I am not aware of any follow-up objections.

Re: The July Galileo Outage: What happened and why

#57

Post by toomuchtodo »

londons_explore wrote: post #52
toomuchtodo wrote: post #17

Earlier quoted context omitted.

Any chance we'll see WAAS reference stations with more autonomy for uploading ionsphere correction data directly to the constellation, instead of having to aggregate at master stations, which then forwards to ground uplinks?

Why would you want that? For slightly more accuracy in a severe ground station outage? Seems only marginally worth it...

More redundancy, less single points of failure.

Re: The July Galileo Outage: What happened and why

#58

Post by Aloha »

ahubert wrote: post #50
makomk wrote: post #12

Earlier quoted context omitted.

The 60 day long-term ephemerides were the older sytem. Autonav on the current GPS satellites is considerably fancier - basically, the satellites carry out ranging measurements between each other and compute their own updated clock and ephemeris solutions on the satellites themselves in a distributed fashion. Specced to provide essentially full accuracy for something like six months, minus ionosphere estimates which c…

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!

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.

Re: The July Galileo Outage: What happened and why

#59

Post by guenthert »

londons_explore wrote: post #53
ahubert wrote: post #50

Earlier quoted context omitted.

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!

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 subtracti…

> A rather simple software radio

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

Re: The July Galileo Outage: What happened and why

#60

Post by londons_explore »

guenthert wrote: post #59
londons_explore wrote: post #53

Earlier quoted context omitted.

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 subtracti…

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

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