Scrutable

Does anyone here have an insight into how accurate this report is ?

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

Not another of Dom's mates is it?

Interested in looking at low-orbit satnav in some detail?
Stanford symposium summary
From November 2016. Big pdf download.

One would need properly equipped satellites with onboard atomic clocks and software and ground support to keep them accurately updated.

Would certainly not trust bojo and-or friends with anything like this.

I'm not sure this is automatically a terrible decision. Buying into a satellite company with all of the design/manufacturing/operating capabilities spun up for one constellation of satellites is a great start for expanding into operating a second one. The plan may not be to build Brexitnav into the OneWeb internet satellites - there are a whole host of reasons why that probably isn't practical. Using/expanding the current satellite bus that is designed for 1000s of units built could prove to be a good way to cut Brexitnav's overall costs.

They're doing this because OneWeb is currently cheap to buy into. SpaceX and Covid has currently killed OneWeb, but having a government backing up OneWeb's internet offering may well make it more attractive to some users (and less attractive to others but would those others prefer a US bases system?). Making it work for Brexitnav will of course will require coherent vision, planning, leadership etc so...yes its a terrible decision right now, and still stupid compared to being in Galileo.

bmforre wrote: ↑

Fri Jun 26, 2020 7:31 pm

A view from ISPreview

That confuses me a bit as it compares a constellation of possible thousands of low orbiting, short-lived satellites with a small number of much larger geostationary satellites, but I thought GPS used dozens of medium-orbiting satellites.

Anyway, my bigger concern is security: we're going from being a full partner in Galileo to taking a 20% stake in a near-failing commercial concern whose controlling interest might be sold to absolutely anyone.

It wasn't necessarily easy to get a photo of a real GPS satellite and not a drawing of one in space.

https://www.lockheedmartin.com/en-us/products/gps.html

They tend to be in 16 hour orbits.

shpalman wrote: ↑

Sat Jun 27, 2020 1:07 pm

It wasn't necessarily easy to get a photo of a real GPS satellite ...

Thanks. Nice espionage. Sort of minivan-sized I suppose.

Boris's world-beating shoebox-sized Brexitnav presumably wouldn't have space for atomic clocks on board but I wonder what the options are, either for having OneWeb build something bigger or whether you can make an innovative viable satnav where the reference clocks are not on board.

Miniature reference clocks are available but need updating against more stable reference once per Earth orbit. See the Stanford presentation.

bmforre wrote: ↑

Sat Jun 27, 2020 2:54 pm

Miniature reference clocks are available but need updating against more stable reference once per Earth orbit. See the Stanford presentation.

Thanks. (Sorry I didn't read it before but I got put off by the "big PDF" comment, but 52MB of slides is a lot less daunting than 52Mb of text.)

Gosh. A $1,000 atomic clock that fits in a matchbox and draws under 120mW. Okay, you get 100x the daily drift of a full size clock so you have to keep resynching them, but wow.

I have to keep adjusting my technology/magic boundaries. (I still haven't quite got over thinking 40 years ago it was crazy to suggest you could make a truly portable receiver which picked up a time signal from multiple satellites simultaneously to tell you where you were.)

As far as I'm concerned we crossed into magic some time ago.

Martin Y wrote: ↑

Sat Jun 27, 2020 3:31 pm

bmforre wrote: ↑

Sat Jun 27, 2020 2:54 pm

Miniature reference clocks are available but need updating against more stable reference once per Earth orbit. See the Stanford presentation.

Thanks. (Sorry I didn't read it before but I got put off by the "big PDF" comment, but 52MB of slides is a lot less daunting than 52Mb of text.)

Gosh. A $1,000 atomic clock that fits in a matchbox and draws under 120mW. Okay, you get 100x the daily drift of a full size clock so you have to keep resynching them, but wow.

I have to keep adjusting my technology/magic boundaries. (I still haven't quite got over thinking 40 years ago it was crazy to suggest you could make a truly portable receiver which picked up a time signal from multiple satellites simultaneously to tell you where you were.)

I remember that about 20 years ago the receiver existed but it didn't have any maps in it, so it could tell you where you were, but not in relation to anything else.

shpalman wrote: ↑

Mon Jun 29, 2020 8:46 am

I remember that about 20 years ago the receiver existed but it didn't have any maps in it, so it could tell you where you were, but not in relation to anything else.

Yeah, my first encounter with a real GPS device was on top of some peak in Snowdonia where a guy was attracting a crowd to ooh and aah at his new gadget, which told you which OS coordinates you were at and helpfully added which OS sheet to look on to find those coordinates. (I recall helpfully remarking that if you didn't know which sheet you were on you were really lost.) It ran on a mere 12 AA batteries.