Hacker News Reader

Comment by perihelions | Hacker News Reader

Seems like a big flaw that low-orbit constellations have a dependency on GPS, which are high-altitude satellites. They're 40x further away and so have 1,600x greater path loss. Why can't they use their own satellites for this?

> "But Starlink receivers use GPS to locate and connect to satellites. “Since its 12-day war with Israel last June," The Times says, “Iran has been disrupting GPS signals.”"

View on HN

This isn’t even true; Starlink can use the local starlink constellation for positioning and the option is available in the customer facing configuration specifically for GPS denied areas (since about two years ago), where it’s been used for ages.

Something else is going on here - perhaps there’s an edge case where Starlink can be made to perform poorly without falling back away from GPS, but I wouldn’t expect this since it’s been “tested” in the most GPS hostile places for quite some time now.

It sounds like Starlink uses GPS to localize the receiver, rather than for any active step in the communication link. Since most receivers are static, I wonder if an effective workaround to this is for the receiver to just remember its last GPS fix for longer, or worst-case allow a manual location specification in lieu of a GPS fix.

A user provided location cannot be trusted for geofencing purposes. A GNSS (GPS or other) is needed sooner or later. This is a legal requirement for sanction and regulation enforcement (US, if not others).

Starlink system inevitably knows the terminal location down to a service cell, which is what, a 20km grain? Good enough for "regulation enforcement".

The satellites know where they are TX beamforming to a fine-enough degree of specificity for geofencing.

The user-provided location would only be used for the initial bootstrapping. After it connects, the Starlink network itself will localize the receiver to within 1 km.

If the user inputs a bogus lat/lon, it would simply fail to connect. There's no way to 'spoof' your location on this type of global satellite comm network.

EDIT It will be interesting to see what anti-censorship and anti-DOS hardening features are coming in future software updates. Full GPS denial bootstrapping is the most obvious, and actually this should be possible without needing to input a location. Adding offline update packages, so signed anti-denial firmware updates can "sneakernet" across oppressive regimes to recover DOSed terminals, would be even better.

Assuming the jamming is coming from close to the horizon, I wonder if one could improvise a choke ring around the antenna with some sheet metal or foil.

Gps is free to use. Running your own gnss service requires an atomic clock and possibly separate transmission hardware, which is possible, but adds cost, volume, and weight.

According to [1], “[o]ne of the current generation of GPS satellites (Block III) weighs over 2,200 kg (4,850 lb), the weight of an average pickup truck. The body of these satellites are 1.8 m x 2.5 m x 3.4 m (5.9’ x 8.2’ x 11.2’) in size”. In comparison, “the current V2 Starlink satellite version weighs approximately 1,760 lbs (800 kilograms) at launch, almost three times heavier than the older generation satellites (weighing in at 573 lbs or 260 kg)” [2]

[1] https://novatel.com/an-introduction-to-gnss/basic-concepts/s... [2] https://www.space.com/spacex-starlink-satellites.html

> Gps is free to use. Running your own gnss service requires an atomic clock and possibly separate transmission hardware, which is possible, but adds cost, volume, and weight.

Thanks you provide some great insights on why starlink didnt use gps but still if starlink wants to focus itself as the uncensorable internet in places like protests etc. I feel like they can probably do this after this recent incident

I just can't feel but sad right now because starlink was still providing activists ways to report outside and that helped protestors a lot and information. Now even starlink got removed because starlink tried to save money and I think might not have thought about what if gps itself gets blocked.

This is giving very bad signals for Iran. Is there any way now that Protestors are able to communicate to the outside world/ activists be able to report data outside?

> if starlink wants to focus itself as the uncensorable internet in places like protests etc

I’m not sure Musk would actually want that though, especially these days.

Why not?

Because Musk is a fickle, unethical individual with poor impulse control and too much money who only talks about high minded concepts like “free speech” and “battling censorship” when it serves his interests at that moment.

You are correct. It’s interesting to watch how ‘free speech’ works on Twitter.

Because his enthusiasm for free speech is variable depending on whether he likes the speech or not.

Why not? Has Musk shut off Starlink? The reporting out of Ukraine was almost entirely wrong. https://en.wikipedia.org/wiki/Starlink_in_the_Russian-Ukrain...

Nobody brought up Ukraine

From your link, with good sources:

In 2022, Elon Musk denied a Ukrainian request to extend Starlink's coverage up to Russian-occupied Crimea during a counterattack on a Crimean port, from which Russia had been launching attacks against Ukrainian civilians; doing so would have violated US sanctions on Russia.[18] This event was widely reported in 2023, erroneously characterizing it as Musk "turning off" Starlink coverage in Crimea.[19][20] SpaceX executives repeatedly stated that Starlink needed to remain a civilian network;[21][22][12] in late 2022, as Starlink was being used as a tool in combat in Ukraine, SpaceX announced Starshield, a Starlink-like program designed for government customers.[23][21] Musk is reported to have said that Ukraine was "going too far" in threatening to inflict a “strategic defeat” on the Kremlin.[24]

Musk, like Trump, has an interesting relationship with Russia. The investigations into that have been quashed, so we don’t get to find out about the rumoured Kremlin calls he was making.

https://www.nytimes.com/2024/10/25/business/dealbook/musk-pu...

> doing so would have violated US sanctions on Russia.

that made me laugh!

The allegation at the time was that he turned off Starlink. That was not true. He did not turn it on at Ukraine’s request because US law prohibited it.

The current administration quashed the investigation into the contact he was having with Putin.

So I guess we get to stick with your story.

https://www.bbc.com/news/articles/cy0l3wl76gzo

Yes, ask their Mossad direct and local handlers (as per Mike Pompeo [1]) about how things are going, I’m sure that this being Mossad they have a ground-based way to get the information out.

[1] https://xcancel.com/mikepompeo/status/2007180411638620659

Mike Pompeo is a private citizen; is there some reason to believe that he has direct knowledge of foreign involvement in these protests? It seems unlikely, and doubly so that he’d actually disclose it if he did.

You and I are private citizens, he’s former US Secretary of State, let’s quit the charade.

“Former” is operative. I don’t see any reason to believe that Pompeo has special insider knowledge here, and sharing it makes zero sense even if he did. The more parsimonious explanation is that he’s a sidelined grifter whose only way to stay relevant is to speculate on social media.

After reading Walter Isaacson's biography of US Secretary of State Henry Kissinger, I would be extremely surprised to find that a former Secretary of State was suddenly out of the loop on major events.

Henry Kissinger was a notorious power broker, and basically remained "in the loop" until the day he died. Pompeo is neither of these things.

But there's an even simpler way to reach this conclusion: given everything you and I know about Pompeo's politics, is there any reason to believe he'd want to introduce doubt about the legitimacy of popular protest in Iran?

GPS comparison is moot in this case, as there's no need for Starlink constellations to provide full GNSS capability, just locating the satellites precisely enough to facilitate beamforming.

Chip scale atomic clocks are quite small[1], have been used in space, and could be part of the existing Starlink satellites. Finding reliable details about the orbital vehicles the internet eludes me.

[1] https://ww1.microchip.com/downloads/aemDocuments/documents/F...

This whole stalink for military use (Starshield) was a scam Elon sold the military from the beginning. Just like his dumb ass tunnels and his self driving cars. He is putting the military at risk.

Is there any actual evidence that Starshield doesn't work substantially as promised?

If you do find some, I encourage you to investigate the source thoroughly and with suspicion.

If the GPS satellites are above the starlink ones how is Iran able to disrupt the GPS signals?

By jamming the receivers on the ground

Ok that makes a lot of sense, thank you.

For legal reasons I base this off of nothing but just turn your jammer to the sky. Could get fancy and point out directly at the satellites since my understanding is it's pretty easy to know where they are.

Edit to add: I do not mean the GPS satellites or the starlink ground terminals. That was not the question so that is not my answer. I mean the starlink satellites

That doesn't work. GPS is broadcast, not bidirectional communication, so preventing the satellites from seeing the GPS receiver does nothing: they're not looking to begin with.

What are you talking about? The jammers are on the ground. Just like receivers on the ground can be jammed with bad RF nearby, so can receivers in space. You just point the bad RF towards the receiver

The GPS satellites aren't receiving anything. The GPS satellites transmit signals, and the starlink terminals (and other users of GPS) receive those signals.

Maybe he's implying they're literally cancelling out the waves like ANC headphones but with emf and a large geographic area.

Wellll you could technically jam their uplink channels, but doing so may get the US in your doorstep quite quickly

More to the point, to do that to this number of satellites on this big an area you'd need nuclear power plant levels of power, and it would only degrade GPS a bit (their clocks slowly desync when uplink is blocked)

My understanding was that each satellite broadcasts a coarse ephemeris for the whole network, and that that “almanac” isn’t accurate for very long (on the order of weeks). Without uploads to the satellites, those almanacs will go stale.

I don’t think the almanacs are necessary for the system to work, in theory. But I believe they’re commonly used by receivers to narrow down the range of possibilities when trying to find a PRN match for a signal they’re getting.

(I’ve dealt with GPS and similar navigation signals for work but am not an expert, this is just the impression I’ve gotten over a few years)

This is a great plot for a B movie or a trashy military action book. “The bad guys are jamming GPS uplink and we only have two weeks until the almanacs are out of date and the whole system breaks down. Millions of innocent Americans will drive into rivers by accident.”

Ok they said the GPS of the starlink satellites is being jammed, and the question was how. The comment I was replying to did not say the terminal, it said the satellite. Maybe that's the confusion

GPS signals are extremely weak, and they're necessarily received from omnidirectional antennas that can't provide much antenna gain. In some sense it's a miracle of signal processing that GPS can ever be received.

There have been developments in receiving antennas that are harder to jam.

Most jamming is horizontal and limited to a few bands. So by having a directional antenna and listening to all services for now it seems to work. But this is a cat and mouse game.

https://furuno.eu/gr-en/marine-solutions/gnss-positioning-ti...

A CRPA should still work.

Musk tweeted a while back that the constellation could be used as its own GPS service, but it wasn’t a priority right now. Maybe later.

Reply on news.ycombinator.com