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flyingturtle
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UK government seeking to repurpose OneWeb satellites for SatNav

Mon Jun 29, 2020 7:27 am

OneWeb being a British company, being registered in the UK and having an UK telecommunication license, is in government debates - first as a rescue package for the ailing company, and secondly, as a base for introducing UK's own satellite navigation.

When the UK leaves the EU, it will not have any say in the EU's Galileo programme.

So, the UK is bidding 500 million lbs err £ for a 20% stake in OneWeb. But it has already been panned by experts:

https://www.theguardian.com/science/202 ... leo-brexit

Given the much lower orbit (polar LEO, 1200 km) and the small size (no room for attaching an atomic clock larger than a Casio F-91W), there are inherent difficulties. It's a huge departure from the true-and-tested GNSS systems that are circling in MEO.
Reading accident reports is what calms me down
 
tommy1808
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Mon Jun 29, 2020 7:40 am

flyingturtle wrote:
Given the much lower orbit (polar LEO, 1200 km) and the small size (no room for attaching an atomic clock larger than a Casio F-91W), there are inherent difficulties. It's a huge departure from the true-and-tested GNSS systems that are circling in MEO.


The clock Problem max be solveable...

https://en.m.wikipedia.org/wiki/Chip-scale_atomic_clock

But having 3 to 4 birds in view at all times may be hard ... but even one at a time may be enough for strategic purposes, and they can be used to distribute real time correction data for all other GNSS for wherever there is a reference station near by.

Best regards
Thomas
Well, there is prophecy in the bible after all: 2 Timothy 3:1-6
 
vrbarreto
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Mon Jun 29, 2020 7:42 am

Another Brexit success story.

https://spaceflightnow.com/2020/03/30/o ... ankruptcy/

Headquartered in the UK but with significant workforces in the US and France this is truly taking back control.. Next step is to paint Blue/Black Unicorns on the side of each satellite and if you try and use it outside the UK you get a message saying 'are you avin a larf?'
 
mxaxai
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Mon Jun 29, 2020 9:19 am

flyingturtle wrote:
Given the much lower orbit (polar LEO, 1200 km) and the small size (no room for attaching an atomic clock larger than a Casio F-91W), there are inherent difficulties. It's a huge departure from the true-and-tested GNSS systems that are circling in MEO.

I cannot see OneWeb replacing a full GNSS like GPS or Galileo. There's no way to launch enough to always have 4+ satellites in view.

The only function those satellites can perform effectively is to broadcast additional data for a (regional) overlay system like EGNOS or WAAS. Which might be convenient for the UK since leaving the EU might also exclude them from EGNOS. One should note, though, that WAAS & EGNOS transmit on the GPS frequencies whereas OneWeb (obviously) uses completely different frequencies. So either you expect users to add a second antenna to their GPS device, or you'll have to replace the OneWeb satellite's transmitter with a different model.
 
tommy1808
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Mon Jun 29, 2020 9:53 am

mxaxai wrote:
flyingturtle wrote:
Given the much lower orbit (polar LEO, 1200 km) and the small size (no room for attaching an atomic clock larger than a Casio F-91W), there are inherent difficulties. It's a huge departure from the true-and-tested GNSS systems that are circling in MEO.

I cannot see OneWeb replacing a full GNSS like GPS or Galileo. There's no way to launch enough to always have 4+ satellites in view.


If the goal is largely to have an independent precision targeting capacity for the boomers one satellite in view will do. You only need four to get a 4D fix if the ground device doesn't have a precise IMU/clock. Would just take a few min instead of a few seconds

So either you expect users to add a second antenna to their GPS device, or you'll have to replace the OneWeb satellite's transmitter with a different model.


I would assume it's easier to add GNSS receivers to Oneweb terminals.

But yeah, seems to be a fairly stupid idea.

Best regards
Thomas
Well, there is prophecy in the bible after all: 2 Timothy 3:1-6
 
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flyingturtle
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Mon Jun 29, 2020 12:20 pm

tommy1808 wrote:
If the goal is largely to have an independent precision targeting capacity for the boomers one satellite in view will do. You only need four to get a 4D fix if the ground device doesn't have a precise IMU/clock. Would just take a few min instead of a few seconds


Do you think along the lines of COSPAS/SARSAT? Where the satellite would broadcast a time signal, from which the receiver on earth could figure out the satellite's location, and from the Doppler shift the receiver would calculate its relative velocity compared to the satellite, and then both data allow you to calculate your position?
Reading accident reports is what calms me down
 
tommy1808
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Mon Jun 29, 2020 1:55 pm

flyingturtle wrote:
tommy1808 wrote:
If the goal is largely to have an independent precision targeting capacity for the boomers one satellite in view will do. You only need four to get a 4D fix if the ground device doesn't have a precise IMU/clock. Would just take a few min instead of a few seconds


Do you think along the lines of COSPAS/SARSAT? Where the satellite would broadcast a time signal, from which the receiver on earth could figure out the satellite's location, and from the Doppler shift the receiver would calculate its relative velocity compared to the satellite, and then both data allow you to calculate your position?


No, and I am not sure of that could be precise enough.

I mean that you dont need to receive 4 satellites concurrently if you know how much time has passed, and how much distance you have been travelling between satellites signals. Four satellites would pass over you in rather short time.

Best regards
Thomas
Well, there is prophecy in the bible after all: 2 Timothy 3:1-6
 
mxaxai
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Mon Jun 29, 2020 2:18 pm

flyingturtle wrote:
tommy1808 wrote:
If the goal is largely to have an independent precision targeting capacity for the boomers one satellite in view will do. You only need four to get a 4D fix if the ground device doesn't have a precise IMU/clock. Would just take a few min instead of a few seconds


Do you think along the lines of COSPAS/SARSAT? Where the satellite would broadcast a time signal, from which the receiver on earth could figure out the satellite's location, and from the Doppler shift the receiver would calculate its relative velocity compared to the satellite, and then both data allow you to calculate your position?

I think it's more like generating "virtual satellites" from a single satellite. Usually, GNSS provide 4 pseudoranges (one from each satellite) at the same time, so your receiver can figure out the actual range and time. You could also provide multiple pseudoranges from a single satellite, but each at a different time. You would need to know the precise time difference between each measurement (i. e. an atomic clock on the receiver) and the movement of your receiver between each measurement (i. e. a precise IMU).
 
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flyingturtle
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Mon Jun 29, 2020 8:18 pm

Ahhhh, thank you, mxaxai and tommy1808!
Reading accident reports is what calms me down
 
tommy1808
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Tue Jun 30, 2020 4:51 am

mxaxai wrote:
flyingturtle wrote:
tommy1808 wrote:
If the goal is largely to have an independent precision targeting capacity for the boomers one satellite in view will do. You only need four to get a 4D fix if the ground device doesn't have a precise IMU/clock. Would just take a few min instead of a few seconds


Do you think along the lines of COSPAS/SARSAT? Where the satellite would broadcast a time signal, from which the receiver on earth could figure out the satellite's location, and from the Doppler shift the receiver would calculate its relative velocity compared to the satellite, and then both data allow you to calculate your position?

I think it's more like generating "virtual satellites" from a single satellite. Usually, GNSS provide 4 pseudoranges (one from each satellite) at the same time, so your receiver can figure out the actual range and time. You could also provide multiple pseudoranges from a single satellite, but each at a different time. You would need to know the precise time difference between each measurement (i. e. an atomic clock on the receiver) and the movement of your receiver between each measurement (i. e. a precise IMU).


more eloquent than i could have put it.

best regards
Thomas
Well, there is prophecy in the bible after all: 2 Timothy 3:1-6
 
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Aesma
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Sat Jul 04, 2020 1:33 am

The UK could stay in Galileo no problem, it chose to leave it (my guess is it will come back).

As for the money, some friend called Dominic Cummings and it happened, don't bother looking for a reasonable explanation.
New Technology is the name we give to stuff that doesn't work yet. Douglas Adams
 
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Nomadd
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Sat Jul 04, 2020 3:53 pm

There's a lot of "spherical cow" figuring going on in here, that tends to ignore real world issues. Oneweb sats have no potential for any kind of real location service. You can build an entirely new satellite and put a "Oneweb" sticker on it and claim it's a modification, but that's only going to fool people who think bicycles have the right of way over dump trucks.
 
mxaxai
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Re: UK government seeking to repurpose OneWeb satellites for SatNav

Sat Jul 04, 2020 5:08 pm

Nomadd wrote:
There's a lot of "spherical cow" figuring going on in here, that tends to ignore real world issues. Oneweb sats have no potential for any kind of real location service. You can build an entirely new satellite and put a "Oneweb" sticker on it and claim it's a modification, but that's only going to fool people who think bicycles have the right of way over dump trucks.

Yes, agree. There are theoretical ways to repurpose those already in space and you could reuse the satellite bus for new payloads. But it'd be quite some work to modify the design and the production process.

In the best case, the UK government finds utility in the communication services OneWeb was designed and launched for.

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