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Starlink signals can be reverse-engineered to work like GPS
- deleted 4y ago[deleted]
- gjsman-1000 4y agoWell… if it is that easy, might as well make the sequences proprietary again (change them for security), but it should not cost very much after all to add such functionality. At least not nearly as much as Elon thought.
- belval 4y agoI think the article makes it clear that SpaceX does not care much about security here. It's more that they don't have (engineering) bandwidth to actually put something together and sell/support it. Focus is a very real thing in business, starting an additional product that has a minimal overhead can still end up ~2-3 years later as a massive cash drain with a complex hierarchy of workers with a very small ARR. That's why you take on customers before building it.
- iwillbenice 4y agoThe one note I will mention about SpaceX and caring about HW/terminal security is the subsidized cost. SpaceX is retailing the terminal I bought for $500, while I understand the hardware all-in is north of $2000. In these scenarios you will usually see the vendor default to locking down the platform/hardware, if for nothing else to prevent people from buying it and re-purposing it due to subsidized components included.
- arsome 4y agoI mean I think both directions here make sense: SpaceX doesn't want to invest engineering effort on this when they're not even profitable and there's no profitability to be seen from navigation, while researchers can do a little reverse engineering and make something workable without the need for that engineering investment.
- axg11 4y agoThere's no profitability from navigation? Starlink could charge a massive premium for high resolution GPS.
- arsome 4y agoBut GPS is already so widely deployed and you can't really compete with free.
- ceejayoz 4y agoIf someone starts taking out the 24 GPS satellites - a new anti-satellite weapon, or an interceptor satellite like the X-37 is speculated to be - being able to do it off Starlink's thousands as a backup would be extremely appealing to the US government. (After all, this is the same organization that's happy to pay out the nose to keep ULA alive to have redundant launch options.)
- manquer 4y agoGPS satellites don’t sit in LEO . All ASAT weapons demonstrated so far by any country has been only for LEO based satellites.
- ceejayoz 4y agoThat would be why I said "new", yes. Given that we can get satellites to GEO, we can presumably get one that goes boom up there, should we be so inclined.
- manquer 4y agoIt is not that simple, the high orbits mean it is very very difficult for solid propellant based ICBM variants to reach with a meaningful payload, also given the orbits it is much easier to perform early detection and make evasive maneuvers. Also remember even if you did launch on liquid rockets, It is not easy to launch them in quick succession or with stealth. Liquid rockets needs a lot of time to load fuel, needs a ton of auxiliary equipment( cryogenic fuel storage at-least) and have limited shelf life once loaded which means they are limited to few known sites which you can quickly take offline after the first attack/launch. Solid rockets/ICBMs can be launched from variety of platforms some of them very mobile and also given their lower footprint - Silos and other sites can be hidden and missiles moved around to retain the strike capability. ASATs are primarily designed to target low flying spy sats[1], taking few key ones out can at the right time can potentially deliver few hours of advantage in a battle before alternative sats can be rerouted. Communication and navigation sats on the other hand are designed to operate even during normal times when few go offline without loss of operational capabilities . [1] Also this is much easier to justify domestically and globally than say communication ones even if they were dual use.
- ortusdux 4y agoI've been wondering how precise Starlink could get with positioning if they put some effort into it. Maybe add some dedicated hardware to the much larger 2.0 batch of satellites. If they felt they could surpass what is available via GPS, I could see them integrating Starlink uplinks into Teslas to aid their self-driving efforts. Adding always on data would be a bonus.
- oliwary 4y agoYes! This could be so exciting. Given that starlink satellites are much more numerous and much closer than GPS satellites, I wonder what the lower bounds are for possible accuracy. Imagine a globally available positioning system with 1cm accuracy and 30 updates per second... (compared to 1 time per second for GPS) This could be a revolution for VR, robotics, logistics and so many other fields.
- aredox 4y agoAnd for cruise missiles. (Maybe you should read why GPS is not more accurate: it's not a technical limitation, it's done on purpose. Also try to read up on Chesterton's Fence.)
- snovv_crash 4y agoThis changed over 20 years ago, GPS no longer has artificial limitations for accuracy. You can't get commercial GPS receivers licenced unless you restrict the altitude and speed they operate at, but a dedicated self-built receiver technically doesn't need to have these restrictions. There are SDR+software projects that do this, which could technically be used for ICBM guidance with no restrictions.
- BenjiWiebe 4y agoThe restrictions are for high speed and high altitude, not accuracy. You can use the GPS module at full accuracy if you aren't really high or going really fast. Model (high-powered) rocketry trackers occasionally run into this, but usually not an issue since you need the location data to find where it lands, and it's going pretty slow under chute.
- dr_orpheus 4y agoI think there is a bit of an issue here that isn't addressed in the article. They reference using the SpaceX published ephemerides which are created from the GPS receivers onboard the SpaceX satellites: "SpaceX satellites regularly downlink accurate orbital information from onboard GPS. We use this orbital information, combined with planned maneuvers, to accurately predict future ephemerides, which are uploaded to Space-Track.org three times per day" [0] So using the positioning information of the SpaceX satellites is already dependent on GPS. Saying that it could be used as a backup to GPS is a bit non-sensical to me. Sure you could go back to using ranging measurements for each of the satellites to get TLEs from NORAD or LeoLabs or one of the other commercial space tracking companies, but it would likely be less accurate and not updated as frequently as the SpaceX satellites don't have a precision clock onboard for timing and propagation like the GPS satellites do. [0] https://www.spacex.com/updates/index.html https://www.spacex.com/updates/index.html
- jenny91 4y agoThey're different failure modes. It's unlikely the GPS constellation will go dark anytime soon. It's much more likely you're in an area without good view of the (few) GPS satellites required for a fix; or that there is GPS jamming, etc.
- dr_orpheus 4y agoAh, that is true I didn't consider it from that perspective. It may also serve as a decent anti-spoofing measure if you compare the two results for position that you are getting directly from GPS vs from the Starlink satellites.
- helsinkiandrew 4y agoPresumably GPS can be jammed locally on the ground and confuse ground terminals but not at the range required to block the SpaceX satellites reception in low earth orbit.
- ortusdux 4y agoAre the phased array antennas utilized by the starlink satellites and user terminals more resilient to jamming?
- rongopo 4y agoThat's how GPS works, it was initially intended for something else --- was it for detecting nuclear blasts?
- hotpotamus 4y agoI thought the idea for GPS went back pretty much to Sputnik. People realized pretty quickly they could track it by timing its signals from a known location on Earth and then also quickly realized you could reverse that and figure out where on Earth you are once you have enough timing signals from known locations in space. It just took a bit for the computers to get small enough and for us to put up the satellites.
- dingaling 4y agoThat's correct and led directly to the US Navy's doppler-based Transit GNSS that operated from 1961 until 1996. Navstar / GPS emerged as a joint project in 1973 based on individual services' research into a better form of GNSS.
- MichaelCollins 4y agoNot for detecting nuclear blasts, but rather for directing them. The primary motivation for Transit/NNSS, the first satellite navigation system, was to provide location information to missile submarines so they could calculate firing solutions for SLBMs. The submarine needs to know where it is so it can tell the missile where to go. Detecting nuclear blasts from space came shortly later with Project Vela. Those satellites didn't depend on something like GPS because the position of each satellite at any given time could be calculated from its known orbital parameters; no need for radio navigation.
- outworlder 4y ago> The submarine needs to know where it is so it can tell the missile where to go. That reminds me of "the missile knows where it is because it knows where it isn't" https://www.youtube.com/watch?v=bZe5J8SVCYQ https://www.youtube.com/watch?v=bZe5J8SVCYQ
- ck2 4y agoMore and more devices already have GPS L5 chips which is accurate to a foot The problem is altitude. I can't get my watch or phone to give me proper altitude anywhere. Within a meter would be amazing forget a foot. https://barbeau.medium.com/tl-dr-dual-frequency-gnss-on-android-table-of-devices-9be4bbb83a7b https://barbeau.medium.com/tl-dr-dual-frequency-gnss-on-andr... https://barbeau.medium.com/crowdsourcing-gnss-capabilities-of-android-devices-d4228645cf25 https://barbeau.medium.com/crowdsourcing-gnss-capabilities-o... https://docs.google.com/spreadsheets/d/1jXtRCoEnnFNWj6_oFlVWflsf-b0jkfZpyhN-BXsv7uo https://docs.google.com/spreadsheets/d/1jXtRCoEnnFNWj6_oFlVW...
- t0mas88 4y agoTry a WAAS or more general an SBAS receiver, they give accurate altitude information. Accurate enough to land an aircraft with.
- ck2 4y agoWAAS is fascinating. Interesting that older Garmin watches used to have WAAS but because it's a "north america only" ability it seems to have been discontinued after the first Fenix/Epix https://www8.garmin.com/aboutGPS/waas.html https://www8.garmin.com/aboutGPS/waas.html
- t0mas88 4y agoWAAS is North America only, because that's the specific name of the local system. The generic term is SBAS, which works in Europe, Japan, India, Russia, China and soon also Australia and parts of Africa. It's used by modern airplanes to do GPS (GNSS) approaches, so expect it to be rolled out everywhere over time. Some systems/countries are listed here: https://en.wikipedia.org/wiki/GNSS_augmentation https://en.wikipedia.org/wiki/GNSS_augmentation
- borissk 4y agoIf one way or another Starlink starts providing precise positioning data it will turn their satellites into a valid military target in case of a war. E.g. if China invaded Taiwan, they may take down the part of the constellation that passes over China (if they can cheaply mass produce and launch interceptors).
- deleted 4y ago[deleted]
- aredox 4y agoThey could easily saturate the whole LEO where starlink operates with schrapnel - and any damaged sat would add more schrapnel, as described by the "Kessler syndrome".
- baq 4y agoThere's nothing easy about what you propose. It requires launch capability similar to what SpaceX has, i.e. state of the art.
- shadowgovt 4y agoGiven that they have a working space station, I'm certain China has enough launch capability to make the Starlink orbit hell with several well-placed rockets undergoing very dirty disassembly in orbit. (In fact, among the things that makes that scenario less likely is the fact they have a space station and would like to keep visiting it without worrying about passing through a Kessler cloud).
- shadowgovt 4y agoIt's a neat trick, but I wouldn't rely on it for the same reason I recommend against relying undocumented behavior in an API: if Starlink isn't intended to be a global positioning system, then they can change anything in the protocol at any time to improve its utility for its intended purposes as the expense of its utility for GPS. That's annoying if your RPC library is now broken because you assumed order of unrelated events wouldn't change. In a GPS it can direct you off a cliff.
- RajT88 4y agoThis is good advice, for sure, and I've received it from wise colleagues in the past. Where I land on this is: Undocumented behavior can be useful if you're doing something which is short in duration, and narrow in purpose. Don't build a product off it, though. I guess in this case, it could be useful for a fallback positioning mode for the military or something.
- madars 4y agoMassively impressive! A very exciting paper https://arxiv.org/abs/2009.12334v4 https://arxiv.org/abs/2009.12334v4 from the first two authors shows how Starlink can be fused with ordinary GNSS to get extremely impressive +56 dB anti-jam advantage (see Figure 1).
- loceng 4y agoElon on Twitter was saying it can be made much more accurate than GPS, just that it's not a priority for them.
- CamperBob2 4y agoMy guess is that the reason they terminated work with the UT Austin researchers is that they've signed a commercial deal with someone else that hasn't been announced yet. GPS-independent PNT (position/navigation/timing) is a significant area of both market and military/civil government interest right now, and has been for a while. They won't be indifferent to it at SpaceX or at any other organization that operates or plans a constellation.
- pencilguin 4y agoMuch more valuable would be to add software to the sats that turn them into a globe-sized radio telescope. In principle, the terminals would also be able to participate.
- BonoboIO 4y agoElon says at lot of things when the day is long
- natch 4y agoTV satellite signals have been used like this for decades. I sat through a company pitch on this and one of the advantages was it (TV, not Starlink) penetrates buildings and for example underground parking lots way better than GPS signals.
- Animats 4y agoThis is straightforward to do if you have some reference ground stations listening to the satellites. That's how WAAS works. If you have ground reference stations receiving and broadcasting offsets, you can derive navigation info from any set of long-range RF sources which have some pattern to which you can sync. The U.S. Army has "pseudolites" which do this for short distances.[1] These are used as a backup to counter GPS jamming. [1] https://www.army.mil/article/169033/Pseudolites_preserve_position_information_during_GPS_denied_conditions https://www.army.mil/article/169033/Pseudolites_preserve_pos...
- t0mas88 4y agoYou can even do this with simple AM radio stations. Tune an aircraft's ADF to the radio station frequency, get a bearing to the transmitter and then do the same with another station. From both bearings you can figure out where you are as long as you know where the transmitters are. It's conceptually similar to what they did here with the Starlink signal but using very different technology.
- yazzku 4y ago“OFDM is all the rage,” says Mark Psiaki, a GPS expert and aerospace professor at Virginia Tech. Did a Virginia Tech professor really say "it's all the rage"?
- stuckinhell 4y agoOh probably shouldn't be sending those the iranian revolution then.
- mmaunder 4y agoGPS is also coupled with WAAS which relies on a network of ground stations at known coordinates to determine GPS error. These errors are caused by bulges in the ionosphere that throw off timing. Error is calculated, broadcast up to satellites and then rebroadcast down to GPS receivers that are WAAS enabled. This is known as a satellite based augmentation system. The other satellite nav systems that compete with GPS are building similar augmentation systems (like GAGAN, EGNOS, MSAS and SDCM). These systems are required for precision approaches like LPV for aircraft on instrument flight plans. Regular GPS precision due to ionosphere changes is too low. They've enabled the FAA to lower the minimums for GPS approaches down to levels that are close to ILS, removing the need for expensive ILS installations at many regional airports. So replacing GPS isn't just about creating a system to locate a point in space. You'd need to replace critical systems like WAAS that enable precision approaches during instrument conditions, for example.
- FredPret 4y agoIt’s mindblowing how many wrinkles there are to iron out in a complex system. Who knew that the ionosphere bulges!
- pixl97 4y agoSpaceX for one. When solar storms occur they have to release newly launched satellites at a higher altitude to avoid being slowed down by a puffed up atmosphere. Just recently they lost a few starlink sats to this effect.
- pencilguin 4y agoRather more than a few. Managed to save a few, instead. Expensive lesson.
- ajross 4y agoFWIW, that particular problem isn't likely going to be an issue for Starlink. Starlink satellites orbit at 550km vs. 20000km for GPS. The transmission is much (much) closer to a straight line approximation and ionosphere refraction is negligible. In fact, the line of sight transmission to and from a Starlink satellite is likely to be significantly better than that between an airliner and its local WAAS station, which is confounded by ground reflections. (Edit for clarity: WAAS is just digital data, this isn't an actual error in the signal. The point is more "you have to spend more engineering effort on the transmission environment of the correction signal for GPS than you do on the actual signal for Starlink")
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- mattanimation 4y agoI had an inkling that Todd's team would be behind this. They do awesome work!
- chatterhead 4y agoDo Starlink sats have the capacity to store IPFS data?
- mlindner 4y agoI'd assume not, at least no more than any other network router has the ability to do so.
- chatterhead 4y agoIf it did; which wouldn't take much - it sure would change what he was building. I'm posting too fast so I'm editing this: If Elon slapped storage into each of those sats he could use a system like IPFS to store data and create say... a world wide censorship-proof social media company that not even governments could block (without direct action).
- guipsp 4y agoI... What?
- imron 4y ago> And so we [SpaceX] have to focus completely on staying out of bankruptcy. We cannot afford any distractions.” Looks like Elon got them to build it for free.