A lot of comments seem to be about spoofing. Remember that there are multiple humans in the loop -- experienced pilots and experienced air traffic controllers -- and multiple levels of redundancy. Pilots have access to barometric altitude, radar altitude, traditional VHF navaids, TCAS-issued resolution advisories (based on directional antennas, not GPS)... in addition to GPS. Air traffic controllers have primary radar and secondary radar in addition to ADS-B information.
You could probably cause a lot more trouble by buying an aviation radio off the shelf and just chatting on the frequency or issuing fake clearances if you want to be a mass murderer.
Ultimately the system comes down to many systems working together, not one stream of commands between two computers.
> buying an aviation radio off the shelf and just chatting on the frequency or issuing fake clearances if you want to be a mass murderer
Incidentally, I am happily surprised that that never seems to happen. One could so easily create so much chaos at an airport... There is no authentication whatsoever.
The problem with _requiring_ authentication is that it can create a safety issue when communications break down. As a pilot it's not a bad idea to carry a spare handheld radio, or even use a cel phone, when you lose communications.
I was flying once with a buddy of mine who was Pilot-In-Command and we lost (or thought we had lost) our radio on an IFR flight back into the Bay Area. What had happened was the Push-to-Talk button on the yoke had become stuck and we were transmitting the entire time while attempting to diagnose what was wrong. This happened for about five minutes. Thankfully he had a handheld radio in his flight bag, and when we turned it on we figured out really quickly what was going on.
In that scenario, if we didn't have the handheld radio, it would have caused a worse problem.
Pilots do train for communication failures. ATC at most airports has a number you can call to be patched through if your radio stops working and I've heard multiple cases of people having to use it.
In the worst case, there are non-verbal methods of communication that pilots or ATC can employ (ATC can send light signals, pilots rock their wings to signal communication failures, etc.)
Seven six, on the fritz! (Squawk 7600.) There’s an established, cut—and-dry procedure for when an IFR aircraft goes NORDO. Even without that handheld, you would’ve been fine.
Every airplane between you and your destination, on the other hand, would find themselves being rerouted.
I didn't mean to imply that we thought we were in any kind of imminent danger. There were three pilots (including myself) in the plane, all whom had trained in a highly congested area.
My point was that having the handheld radio allowed us to trouble shoot the situation. Without the radio there would have been a lot higher workload and less of a margin for safety.
Plus you might've inadvertently blocked the frequency longer (for other participants) if you hadn't been able to diagnose it. So it was definitely a good thing you had the handheld aboard: even if there was no imminent danger for you, it would have been an inconvenience for many.
Moving too fast for the cell network to keep up, I'm guessing. Before it manages to handoff to the next cell, you're actually leaving that one already.
I'm kind of wondering if there even needs to be. If you keyed up on frequency near a major airport as described in the GP, I'm pretty sure the FAA and FCC would be working together to track you down in short order. I could see the argument that it would be good to add authentication to the radios to complement the strict enforcement for a sort of belt-and-suspenders approach. However, I think a more pressing concern for aviation radio is that is is kept simpler, and thus with fewer failure modes, and thus more reliable Because when you need that radio in an emergency, that has to be the worst possible time to have to deal with authentication hiccups.
VHF radios are relatively easy to locate by direction finding techniques, using for example a doppler direction finding array. The FCC's enforcement division is well-known to possess SUVs with this kind of equipment discreetly installed, although due to their famously limited budget you aren't too likely to see one in the wild. On the other hand, though, many large airports have such equipment permanently installed (e.g. RFEye).
I personally would volunteer to be on one of the teams in another van with directional antennas to triangulate your transmissions and shut down you ASAP.
The fact that no one has ever truly tried that sort of poisoning of radio calls is more due to the tower and aircraft having a very well defined set of calls, so that the likelihood of false transmissions being able to cause havoc is minimized already.
I agree with another commenter that aviation radio systems should be the simplest, most reliable systems possible, and have that layer of communication depend on proper radio call discipline and no more.
My question was of theoretical nature, i'm not up to mischief of that sort. Though i'm often thinking about the vulnerabilities of our technological society, and the (false) assumptions we have about that. Compare it with lock picking.
Most are easily bumped, or not even bothering with that, the door kicked down, some window used instead, and so on. Now, when someone kicks your door down, that's getting noticed, sooner or later.
But what about cheap SBCs dropped somewhere with a battery and some custom periphery working as a relay? Of course the SUVs could find that. After the fact.
Pulling these kinds of attacks - especially undetected - requires a certain level of intellect and education that should also be unaffected by things like substance abuse that hamper systematic planning. People with that level of capability almost always manage to create sufficiently comfortable life situations for themselves that they they lack motivation to do so.
Problems happen when either (1) technology to do harm becomes commoditized and freely available so less capable people can acquire and use (eg. Easy conversion of semi automatic to automatics, commoditized hacks for script kiddies) or (2) capable people feel they're been sufficiently wronged that they don't care about the consequences of revenge (pretty much all the really big headline terrorist actions)
Most intelligence activity on prevention focuses on (2) since pulling off such actions generally requires the capable planners to coordinate with less capable "feet on the ground" who can give things away. However capable people acting alone which happens occasionally is pretty much impossible to stop (Timothy McVeigh, Ted Kazynski, Kaloyev)
It actually happened near me once when a local crazy guy got mad that planes were flying near his house (he bought a house right across the street from the municipal airport) so he found an airband radio and started yelling at them every time they came too close for his liking.
Toronto Centre is in the top level of the ATC hierarchy and is a geographic area rather than specific to the city of Toronto. Airband AM only has a range of 50-200mi in flight so they have outlying stations, usually colocated with VOR stations IIRC.
He probably got lucky and had a station within 5-10 miles of his bathtub...
And most major airports have systems like RFEye or AIRPORT-SHIELD. You would be _immediately_ pinpointed with a remarkable level of accuracy from 3-6 sensors.
Especially near major metro areas, unintentional interference is a daily issue. These systems immediately triangulate sources of interference in a wide band. Or you have simpler systems like UMS100 that just do alerting and you send out an engineer with a wand to walk around for a bit to triangulate it.
These could be pretty easily defeated through a multitude of tactics. They're just being pitched as a stop gap solution against the low hanging fruit like morons with drones or a drunk person with an airband handheld.
With an omnidirectional antenna, sure. With a high-gain antenna, no. The attacker could entirely avoid the RFEye or AIRPORT-SHIELD. The attacker could pick a specific aircraft to pester, with no other aircraft able to listen.
Add some fancy voice synthesis, and it gets interesting. The attacker could clone the voice and style of the air traffic controller. The attacker could provide enough power to quiet out any other transmissions. To keep the air traffic controller incompletely aware, the attacker could provide interference (just to the tower) whenever the victim aircraft begins to transmit.
If you live in Florida, you can go down to the pawn shop, buy a gun, drive over to the airport and start shooting at planes. Doesn't take much sophistication to cause a lot of harm.
With state sponsored terrorism, the risk isn't that the Feds will put the agent away forever, it's that the USG (and, incidentally, other particularly allowed countries) will identify that it is state sponsored terrorism and treat the attack as exactly what it is—simultaneously and act of war and a gross violation of the laws of war.
actually, I'd think state sponsored terrorism would have the resources to get away with it.
Just send the voice data through a raspberry pi to a remote location and carry out the attack from there. You could send voice data through a TOR-like protocol or something to keep you anonymous, if that's important. You could maybe rig some explosives to go off if the FBI/FCC/FAA gain access to the attack point, to prevent them from recovering evidence.
Lot's of police/fire radio systems are similarly without authentication, so you could amplify the mayhem by doing the same thing to those frequencies.
> Incidentally, I am happily surprised that that never seems to happen. One could so easily create so much chaos at an airport... There is no authentication whatsoever.
One of the reasons why airband radio uses amplitude modulation is so that a much more powerful transmitter (ground based, operated by air traffic control or tower personnel, with access to very high Tx powers), can transmit on top of spurious transmissions coming from low powered aircraft or handheld transmitters. The big ground based Tx can step on an interloper and communicate its message to all aircraft on the same frequency.
Given that then ADS-B mandate was just a couple weeks ago, it seems logistically odd that secondary radar would already be turned off.
More generally, my understanding was that the FAA was keeping primary+secondary radar around to augment ADS-B via sensor fusion. I know the "reply" light on my plane's radar transponder still lights up regularly, so at least out here on the west coast the secondary radar is still active. :)
I've also heard there's a longer-term plan to consolidate ATC radar into the NOAA weather radar stations, once they upgrade weather radar to phased-arrays at some unknown point in the future. The marginal cost to keep secondary radar running in that environment is basically zero.
That said, they have certainly been turning down many of the redundant VOR stations as part of MON, and they just turned HIWAS off last week.
I don't think anyone really misses LORAN, though. ;)
So then if everything goes to ADS-B and GPS, doesn't that create a potential single-point-of-failure scenario, as isn't the data that ADS-B sends out itself derived from GPS? Having all navigation information come from a single source strikes me as about a good idea as the single AoA sensor on the 737MAX.
I'd like to be wrong about this, but I'm not sure how I am. How am I potentially wrong about this?
If you shut it all down and something catastrophic somehow goes wrong with GPS, it will be very difficult to get the thousands of planes in the air back onto runways.
They've been reducing the number of redundant ground stations lately as part of a project called "Minimum Operational Network", or "MON". (Mostly on affecting the east coast.) But they're explicitly making sure there's enough coverage that you can get a VOR signal anywhere above 5,000 feet AGL.
Not too familiar with aviation or IFR.
Isn't VOR primarily a beacon that you use to orient yourself, doesn't seem like it helps the ATC maintain separation etc..
IFR separation does not have to depend on radar. Though radar procedures are the norm, there are non-radar procedures wherein ATC can issue instructions (clearances) that provide separation for airplanes who are all navigating themselves with respect to ground-based or satellite fixes. In that regard, VORs help ATC maintain separation.
Secondary radar is very much alive in the US. Forget to turn on your transponder (whether or not you are ADS-B out equipped) and how long until ATC notices? For me, it's usually been before I'm through 400' AGL. Or, as tjohns mentions, just look at how often your reply light flashes.
From the FAA itself:
"The Mode S SLEP Phase 2 program will implement modifications to the Mode S system to sustain secondary surveillance service through 2028."
Err... The FAA is replacing all their secondary Mode S radars with... secondary Mode S radars with ADS-B capability. That's probably gonna last at least 20 years, once installed.
> Air traffic controllers have primary radar and secondary radar in addition to ADS-B information.
Article is pay-walled so I didn't read, but the title explicitly says 'from Radar to GPS', ie away from Radar altogether. It doesn't say, GPS to supplement radar.
Radar isn’t going away. This article talks as if ADS-B is replacing radar, which it’s not. It’s enhancing radar where radar coverage exists and providing coverage on traffic where radar coverage currently does not exist (usually lower altitudes away from major airports and over the ocean).
Indeed. Not everyone even has to have ADS-B Out. You only need it if you’re going into or over Class C or B airspace, in the Class B veils, Class E above 10,000 except below 2500 AGL, and in Class E over the Gulf of Mexico. That leaves huge swathes of airspace—dare I say most airspace in the US—where ADS-B isn’t required. You could fly across the entire country without hitting an ADS-B requirement. And the only way for ATC to see non-ADS-B aircraft is radar.
It’s not just about seeing you, it’s about seeing everyone around you too. ATC’s job is to separate aircraft and they can’t do that if they can’t see non-ADS-B aircraft. In fact just today I overheard an approach controller vector an American Airlines jet around VFR traffic at 1700’. That VFR traffic was in “non-rule” airspace, where ADS-B isn’t required. (I saw the jet and the VFR traffic from my cockpit.) They won’t be able to do that without radar.
I was under the impression that one of the main drivers of ADS-B is to enable smaller separation between aircraft due to the more accurate position reporting. If that's the case, then radar won't be a useful backup because planes would be closer than the radar can separate them.
Planes under IFR will be as close as ATC policies want to run them. If everything's working and separation standards become 2nm laterally, then when there's a GPS or ADS-B outage, we can just revert to the 5nm separation standards and use radar backup.
That might be easier said than done, though, because there may not be enough space to do that. If you have the airspace packed at 2nm and then you need to revert to 5nm, all the planes will fill 2.5x as much area. Plus, how would ATC safely effect that separation when the planes are closer than resolution of the equipment.
ADS-B and Mode A/C/S (MSSR) are both secondary radar. but the equipment differs, in particular the ground equipment looks different. It could be that the MSSR equipment gets phased out as ADS-B prevails. Primary radar will continue to be used though, in particular at airports (ones other than the many local uncontrolled variety).
Oh, good. I can't read the article (paywall) but was hoping they weren't actually replacing radar with GPS. Using GPS to enhance radar seems a lot better.
I worked for a firm, which studied satellite navigation and implementation for air traffic control, guidance, safety, and ILS. I don't think that will ever happen. There are huge gaping issues with GPS, both WAAS and GBAS. It's very unreliable, especially in bad weather. The old-school RF tower and ILS, which used Carrier frequency pairings by the runway, are way more reliable and propagate bad weather while guiding the plane into a runway. There's also been ongoing issues with truckers, with GPS jammers, which drive by airports impacting the quality of signal for planes coming into runway. Even the GPS signal itself has latency and lag, which prevents the plane from making quick adjustments for avoiding traffic and ILS guidance.
The ATC scenario has significantly more relaxed requirements than ILS, and this change is intended primarily to provide coverage in situations where there is no, or limited, coverage from conventional methods (primary/secondary radar), and likely ultimately to replace the outdated secondary radar system with a space-based one.
ADS-B is not a guidance tool and will not lead to any more usage of GPS for guidance than is currently common - and certainly won't impact ILS. They're just totally different use-cases.
It's actually impossible for GPS to show your current position.
The signals have to be received from each satellite, then processed to yield a position valid at the time of transmission.
Every GPS fix you get is delayed by AT LEAST that processing time. Any filtering adds more lag.
Most navigation systems look at the T(fix) -> T(now) difference and project your now position from the prior fixes. Especially if you're following driving directions as opposed to free movement, then programs like Maps etc project how much further you've moved on the route, not just along your velocity vector.
After a few seconds, though, that projection will stop moving, too, when the gap between last fix and now gets too large.
The position output by a GPS receiver certainly can (will) have lag. That's probably what the poster I replied to was referring to, and I hadn't thought about it.
This change allows every pilot to have essentially a 'radar view' of their surroundings, cheaply. A receiver and an iPad app give them a picture much like the aircraft control tower would have.
Lots of issues I'm sure. It'll be interesting to see how this sorts out.
> he’s seen truckers trying to avoid paying highway tolls, employees blocking their bosses from tracking their cars, high school kids using them to fly drones in a restricted area, and even, he believes, undercover police officers using them to avoid tails
In fact these do exist. I saw a demo a few years back from a company that tracked bogus GPS signals and how they could watch jammers drive around the streets of London all day long.
These guys were doing it because they were tasked with keeping LTE towers synchronized and they did it with GPS time so they were building in resilience to their time sources by measuring the signal level and rejecting anything that came in too strong. Spotting jammers was a side benefit.
The GPS antenna on the LTE tower should only be picking up signals from the sky. Transmitters on trucks would need to reflect off of aircraft in order to cause trouble, which would greatly weaken the signal.
Yes the antenna pattern will attenuate the signal coming from the ground somewhat, but it also doesn't suffer from 182 dB of freespace attenuation like the real signal. It doesn't have to bounce off of an airplane either, the Earth has a layer of atmosphere around it that gets ionized by the sun and is also full of water vapor. We also don't have the ability to build perfect antennas, especially since it has to cover the entire sky (GPS antennas do not physically track the individual satellites).
So their corporate telemetry system doesn't document their long lunch at the strip club which, for other reasons, happens to be located just around the corner from the airport.
I'm pretty sure I parsed it correctly. It's "Truckers (with GPS jammers) who drive my airports...". Parsing it as a list means it no longer makes sense.
A valuable part of the ADS-B out mandate is that planes even as small as mine (a.k.a. tiny) can cheaply (<200$US) pick up ADS-B in and display it on a consumer tablet. My private airplanes now have pseudo radar. Not every airplane in the air is broadcasting, but most are. This is a huge safety win. Almost without exception I'll see airplanes on my tablet long before I have visual on them.
Without ADS-B out on your airplane (which you don't have for <$200), you will only pick up mode-C traffic in your area if there's another airplane nearby with ADS-B out and coded to receive ADS-B in. You would then be intercepting/"piggybacking" the traffic transmissions meant for that airplane.
Fortunately (unpopular opinion among pilots) the FAA is slowly phasing in ADS-B out as required equipment. Starting Jan 1 of this year, you need to tx ADS-B if you're anywhere you'd otherwise need a Mode-C transponder, including around many airports.
There was a talk at DEFCON about this in 2012 [1]. The main issue is a radar system gets its information from ground-based measurements, while a GPS system gets its information from air-based measurements that are later transmitted to the ground station. This means that those reports can be spoofed, or lied about, or absent entirely.
Well, as in the beginning of wifi/cell networks and all such similar technologies, their priority was to make a first adequate and reliable system that reports position. And getting operators to adopt it. Defeating bad actors was not a major requirement.
Maybe if it's shown to be a great practical problem, they'll address it. If not, then no they won't. I'm guessing they won't.
I very recently had my ADSB fail while flying in a piper arrow. I think its probably good to have redundant systems in place, its a core to aviation to do that with instruments. Also, the military jams GPS rather frequently for exercises: https://www.thedrive.com/the-war-zone/17987/usaf-is-jamming-...
Ah the piper arrow. Fond memories of many trips around florida and caribbean in that plane as a kid.
It was my job to "help" with the navigation, using a paper chart and VOR/NDB steam gauge instruments. Dad was able to teach 10yo me how to do this stuff, but it was easy to confuse from/to or think you are tuned to station x when actually you are on Y, etc. Particularly night VFR was hard to be sure you were exactly where you thought you were. We did not fly over open water at night.
Later we got a primitive GPS, no maps just waypoints and lat/lng. That thing was so much easier to use it was night and day. Just dial in a 3 letter code for your airfield, and you get range,bearing,eta.
GPS is a huge improvement to safety and convince, but if it goes out a night or in bad weather there are gonna be some problems.
Really? Where? I overview Edwards AFB last week (with clearance as Joshua Approach gave me a shortcut across the restricted areas,) I flew close to Vandenberg last month, not an overfly, but just on the edge of the airspace, I also flew near Fort Huachucha, AZ which is an Army Intel post. I flew right near the Yuma Proving Ground on another trip. Even flew right on the edge of the series of restricted areas containing Area 51 — not a single place was GPS jammed. Even Camp Peary and a few other extremely sensitive sites aren’t permanently jammed.
Even jamming near Nellis and Area 51 is done by NOTAM and not perpetual.
Maybe there is some permanent jamming somewhere but pilots would know about it as GPS availability knowledge is safety critical.
I was an ATC from 1990-1994 - we were using equipment from the 1960s then and I've heard it hasn't gotten much better - granted I was in the Marines - not the most high tech bunch, but still - we were civilian certified. I was never scared to fly before I knew who the other controllers were - an upgrade will be very welcome - except then you might freak out when you know who is building the software...
If there's anyone in the air control technology industry here, I'm curious what parts of this change get you really excited, and which parts get you really nervous?
The cost. This affects general aviation as older planes will require avionics upgrades. Otherwise I’m excited for the sheer amount of data that will be made available to the public. Now you will be able to track all FAA registered planes
Have you seen any official discussion of the data being made available?
I feel like, for example, I'd be worried if fine-detail GPS data was being published live for example, or live enough to predict where the plane is "right" now...
It's worth noting that this kind of data isn't published by the FAA - rather, ADS-B transponders openly transmit information and anyone who wants to is (at least technically) free to receive it. This includes commercial and hobbyist networks of receivers that report information to web services like this.
The FAA in the US does publish a 'privacy list' of aircraft whose owners have requested that they not be included in services like this, and most commercial providers comply with that list, but enforcement is sparse and several hobbyist projects (e.g. ADS-B Exchange) do not and even emphasize aircraft that have put in such a request, since the tend to be a bit more interesting. A bit of a Streisand effect.
The same situation exists with the similar AIS system used by ships at sea, and has produced concerns over malicious use, but there continue to be plenty of websites that will show you maps of ship locations picked up by their contributing AIS receivers.
So no more low flying smugglers into and out of Canada/Mexico... wonder how they will adapt (beside going dark though they’d notice someone going dark after takeoff).
It will probably be easier to spot them, since very few planes will show up on radar and not on the GPS system. It might be enough to go take a visual immediately once this is fully online.
I thought the way that they historically avoided detection was to quite literally fly below the radar. Wouldn't that still work with this new system, they just wont show up anywhere?
There are lots of other ways it's being monitored. But as for the flying below the radar, there are these along the southern border and Gulf of Mexico:
They'll ignore the rules as I'm sure they already do.
As you'll see from the various documentaries, historically planes operating illegally and/or doing illegal things will fly "under the radar" and keep their transponder turned off to evade the authorities.
To an extent, this sounds terrifying. The first thing that jumped to my mind is that GPS be jammed or spoofed. In fact, the U.S. military in its shift away from COIN to great power competition in possibly highly contested environments is training to have less reliance on GPS: https://www.zerohedge.com/news/2018-01-26/usaf-begins-massiv...
Radar can be jammed too, but I would guess the EM signature powerful enough to track. I don't know if GPS jammers would have that issue.
On a positive note, I think this would pave the way towards integrating commercial drone infrastructure into our airways a lot better!
This isn't about throwing away radar, it's about augmenting the current system with more accurate data for better and safer management of airspace.
Most airplanes already rely heavily on GPS for their own navigation. If GPS is being jammed (or having any other clear issue) they'll fall back to their many other redundant navigation instruments.
If you want to be scared, be scared about spoofing of ILS signals, where a couple of dozen feet of error can be fatal.
Certainly around airports radar will be kept, but there are a few (remote?) places where aging infrastructure will not be replaced.
On the plus side, there are areas that had no coverage (Gulf of Mexico) which now get traffic information from receivers that are easier to run than radar towers.
Radar has been jammed in the past by accident, since home routers now operate on the same band. See https://arstechnica.com/information-technology/2015/09/fcc-a... . 5G coming in doesn't improve matters. GPS is actually reserved, so there's going to be a lot less accidental interference.
Well some stealth is base on spoofing part of a radar return. Absorb as much of the incoming radar as possible and alter the reflection using a phased array. So its not impossible just more expensive.
According to the crew on the USS Zumwalt they can make a 600' ship look as large as a cruise ship or as small as a fishing vessel. This ship is covered in radar absorbent materials and has a giant phased array to accomplish this.
Considering it's unauthenticated, and you can buy a broadcaster in the proper band for $50 at Best Buy and load it with DD-WRT? I'm going with "as easy if not easier than GPS", considering GPS spoofing requires equipment you likely don't already have (a can of Pringles and your current router).
The keyword here is spoof. There's no doubt that you can jam the ground receiver (both radar and ADS-B). The key question is whether you can spoof radar returns as easily as ADS-B transmissions.
We still maintain Loran C[0]. Interesting to note receivers have been developed to grab the radio signal from all available stations, up to 40, and triangulate location with eLoran. It's a nice to have as backup to GPS however I'm not sure if it is effective against jamming or spoofing. So, the navy still teaches celestial navigation to officers. [1]
EDIT: Apparently Loran C was discontinued in 2010.
Loran-C has been discontinued. However, there are occasional ongoing proposals to restore it as "eLORAN" using newer digital transmitting and receiving equipment, to provide a terrestrial backup for GNSS. These have mostly fallen flat for simple funding reasons, but increasing attention to ASAT warfare keeps discussions going.
I can’t read the article (paywalled), but I would expect primary radar isn’t going anywhere around airports.
We still have it, and our commercial planes have been required to have ADS-B transponders here for more than a decade. This is just for en-route tracking.
Regarding posts about spoofing and maintaining radar, it was my understanding that the radar sets that most ATCs used was not actually powerful enough to get direct returns from commercial aircraft, and relied on amplifying transponders to be able to see them. Supposedly only militaries operate radars powerful enough to see aircraft directly. Can anyone who knows more confirm or deny? If that's true, I guess we're already in a world were ATC info could be spoofed.
Note: I only have limited experience with ATC Radar (small number of models in the US).
Based on my experience, ATC Radar have no difficulty seeing commercial aircraft with a high probability of detection and low probability of false alarm.
Source: completed a performance assessment of several such systems in the early 2000s against their legacy counterparts using aircraft beacon systems as a source of “truth”.
If I remember to come back to this later, I’ll write a little post showing the theoretical detection performance of such a system. If you’d like to try the exercise yourself, the relevant worksheet is a Blake Chart and you can look up surrogate parameters for the Radar via checking the ASR-XX pages on Wikipedia (e.g. ASR-9 or ASR-11). Finding Radar cross sections (RCS) for commercial aircraft models is similarly straightforward. The system is logarithmic so as long as you’re in the ballpark you’ll be close.
In the US, ATC radar and military radar are one and the same - the FAA and the Air Force share the Joint Surveillance System (JSS). So, while the JSS has plenty of limitations (including plenty of areas with no coverage even in the mainland US), it's designed to meet the military objectives of being able to locate even non-cooperating aircraft.
The JSS is a descendant of the SAGE system developed during the Cold War to detect soviet aircraft. It has a reduced equipment footprint, but this is generally due to improving radar technology, coverage is similar and the backend data processing systems are much more advanced. The majority of radar sites belong to and are maintained by FAA but report directly to the Air Force air combat system.
Is there any other entity that operates these sorts of radomes? On a regular commute of mine, there is one owned by the federal government that has no sign out front [0], but it's not listed on the JSS page [1].
It took a bit of digging... this is an FAA radar, but not JSS. It's a secondary radar reporting to the Kansas City ARTCC, code ZQJN. Essentially, it transmits an 'interrogate' message in response to which aircraft transponders transmit information on the aircraft. This is the system that ADS-B is more or less a direct upgrade from.
I'm not sure exactly what equipment is installed there, I found an older report listing an ASR-8 at that location but that system is obsolete and inconsistent with a newer list showing it as a secondary (SECRA) site only.
You're very knowledgeable! I've been curious about this for a while. The site and equipment does seem well maintained, so I don't think it has been retired yet.
Well that's interesting. How does that tie in to the story's reported change though? I suppose ATCs might be willing to rely solely on aircraft-reported location and speed, but I kind of doubt the USAF would. If they share the same systems, I suppose no equipment would actually change or be decommissioned.
I think that the article's implication that radar is being 'replaced' refers only to the daily work of controllers, not to the technical system. Both the FAA and the Air Force have strong motives to keep the primary radar system, and it would take many years to decommission it even if they wanted to - but near-100% availability of ADS-B does mean that controllers will use it as their primary source of data, instead of relying on the radar returns which even in areas with good coverage can sometimes come in and out and generally be finnicky.
Consider that controllers currently rely primarily on secondary radar, which while more difficult to spoof than ADS-B is still quite subject to malicious manipulation. They are well aware that a primary radar return with no corresponding secondary radar information is something to sort out, and this won't change with a switch to ADS-B.
Nobody is even suggesting eliminating radar. ADS-B is primarily for aircraft identification, not terminal area location information. A side effect is that it helps with airborne traffic information for airplanes without radar or TCAS.
I hope we can finally see some improvements at SFO. The fact that the slightest impact on visibility can cause 4-5 hour long delays is ridiculous. the SF government has tirelessly blocked all attempts to fix the runways so that planes can land in visibility conditions (fog/rain) with the promise that technology would solve the problem.
The problem isn’t the airport. It’s the lateral separation requirements for IFR aircraft on the ILS. Most airliners can land in 0-0, but you can’t do 0-0 landings on parallel runways with the ILS because of lateral separation requirements.
There is also flow control that is from the FAA — under IFR the acceptance rates are reduced.
The short answer isn’t that SFO isn’t “upgraded” but the rate of aircraft acceptance is reduced under low visibility conditions per the FAA — and for good reason, separation of aircraft.
>GPS JAMMING EXPECTED IN SOUTHEAST DURING MILITARY EXERCISE
>GPS reception may be unavailable or unreliable over a large portion of the southeastern states and the Caribbean during offshore military exercises scheduled between January 16 and 24.
I took flight school a few years ago, and had to learn to tune in non-directional radio beacons, and use VHF Omni-Directional Range tools for navigation. I wasn't allowed to use the GPS until I demonstrated mastery of the others.
Considering that, I suspect the aviation industry will keep both systems working for a surprisingly long time.
This isn’t for pilots to know where they are, it’s for air traffic control to know where planes are.
If GPS were to become the sole way to do the latter, every airplane would effectively get an invisibility cloak that those who want to do evil can activate (and even worse. Switching off the on-board transmitter is less scary than spoofing signals)
Because of that, I would expect they keep using some way to detect planes that don’t tell them where they are, or radios broadcasting “plane P is at X,Y,Z” without a plane being there.
> If GPS were to become the sole way to do the latter, every airplane would effectively get an invisibility cloak that those who want to do evil can activate...
This is already the case. Much of the civilian radar system already relies on transponders to get a good fix on aircraft, via secondary radar. Primary radar coverage (no transponder required) is much more limited. Turn off the transponder and you'll largely disappear from ATC's screens.
> This isn’t for pilots to know where they are, it’s for air traffic control to know where planes are.
Yes, thank you for clarifying. I just explained that I am a pilot, so I did know that.
It was an analogy. Just like the way that pilots have multiple redundant "where are you tools", so too do I think traffic controllers will have multiple redundant "where is everyone" tools.
Because the industry, as a whole, is in favor of multiple redundant tools when it comes to safety.
This isn't about throwing away radar, it's about augmenting the current system with more accurate data for better and safer management of airspace.
Existing non-ADS-B based traffic management requires accurate altimeters and working transponders; we have always been at the mercy of systems that can fail. One of the many reasons for the substantial training of pilots.
Probably a very long time, there are national security reasons to keep American airspace under constant radar coverage and radars get cheaper and better as time goes on.
Living in San Francisco, I've always been curious if GPS will eventually let both SFO runways stay open in poor visibility conditions one widely adopted. Does anyone know?
Most approaches that large airliners are doing are already RNAV (GPS) approaches. The reason they close the parallel runway is because of the current ATC aircraft separation rules.
Apparently WSJ is okay with you reading things if you request the content with the correct incantations. There are a bunch of paywall bypass plugins for Firefox that invoke the magic words. Here's one:
When the Kessler syndrome occurs, all transportation will grind to a halt.
The Kessler syndrome is when collisions between objects cause a cascade in which each collision generates space debris that increases the likelihood of further collisions.
GPS satellites are in geosynchronous orbit, far above any threat of Kessler syndrome and we won't have nearly enough material in orbit that occlusion of the satellites would become a problem for centuries, if ever.
GPS satellites are indeed at much higher altitudes and thus well protected from (highly speculative) worst-care Kessler syndrome scenarios, which occur in low-Earth orbit (<2,000 km altitude). However, GPS satellites are not in geosynchronous orbit (35,7000 km altitude) but rather operate in a medium Earth orbit of about 20,000 km.
Indeed. The GPS birds zip around, a GPS device has to learn (traditionally from GPS itself but downloading from the Internet is much faster if you have Internet and these days most devices can do that) where the birds are in order to turn its relative distance from each satellite into an absolute position on the Earth's surface.
If you have an actual GPS app there's typically a diagnostic screen where can see where the satellites are and see them arrive and disappear from your perspective as they orbit.
just fyi, they're in medium earth orbit, thousands of kilometers below geosynch. it's why you have to have an up to date almanac, to know which satellites you can see right now, and why cold starts used to take so damn long. (listen for 4 satellites at a time, trying to figure out which ones are there, when you have no idea when or where you are.)
(though i agree that kessler concerns are overblown.)
If there's ever a hot world war again, all global navigation constellations are going to be destroyed with ASAT missiles in the first hour of it.
There's a legitimate concern that over-reliance on GPS will cause massive financial and loss of life damage in the civilian sector if it's ever denied through jamming or kinetic attacks or solar storm etc.
This may be true, but note that all the ASAT missle demonstrated to date are only capable of low-Earth orbit, just a couple thousand km from the Earth's surface. The GPS satellites operate at tens of thousands of kilometers higher altitude in medium Earth orbit.
Demonstrating ASAT against a GEO target would cause a major political incident. The LEO ASAT tests carried out to date caused enough outcry as is. Hitting a GEO target is not difficult. Ignoring dedicated ASAT missiles, any modern IRBM or LRBM can be tasked to intercept a GEO target.
Global navigation constellations are certainly going to be one of the first targets in any major hot conflict between world powers.
Realistically, a solar storm is a more likely and less predictable threat. The end result is the same, any critical functionality that relies on GPS will be denied for a prolonged period of time.
Not as an overt blanket capability statement, but e.g. LGM-30 is known to carry ASIP and rumoured to carry THAAD kill vehicles, both capable of intercepting dynamic orbital targets. LGM-30 climbs to 100km altitude before deploying the payload bus, which gives it ample range to hit GEO targets anywhere in the hemisphere.
Other thing I completely forgot to mention is that all existing global navigation constellations orbit at MEO, not GEO. Which puts them within speculative range of demonstrated ASAT weapons and allows for even longer reach from a launch vehicle like LGM-30.
> LGM-30 climbs to 100km altitude before deploying the payload bus, which gives it ample range to hit GEO targets anywhere in the hemisphere.
This doesn't make sense to me. Could you explain further? LGM-30 is a land-based ICBM designed to strike targets on the surface of the Earth, and hence to take a (just barely) sub-orbital trajectory <13,000 km from point-to-point, with maximum altitude a few hundred km. Wouldn't its thrust capability have to be drastically upgraded to reach 20,000km in altitude, where MEO satellites like GPS are?
This isn't about using GPS as the only navigation aid in an airplane. It's about augmenting the current air traffic system with additional, more accurate data to help manage airspace.
ADS-B doesn't change anything about how a plane navigates. That's still done with a plethora of redundant instruments, all working together.
That is known as Selective Availability and according to the US Government there is no intention of enabling it again [1]. New GPS satellites are apparently being built without the Selective Availability capability [2].
Isn't low precision something like +/- 15 feet? For ATC, that seems more than good enough when they keep jets a mile+ apart. It just needs to be more precise than radar.
The government claims that they won't enable selective availability any more (which is less useful as a protective mechanism anyway since multi-protocol receivers can use GPS / Galileo / GLONASS / Beidou).
But if SA was enabled:
Before it was turned off on May 2, 2000, typical SA errors were about 50 m (164 ft) horizontally and about 100 m (328 ft) vertically
There are also ground based systems at airports which increase reliability / integrity for things like simultaneous parallel approaches. [1] says to within +/- 1m horizontal and vertical.
I would hope aircraft would have multiband receivers that also support GLONASS, Galileo, and BeiDou. There's also Japan's QZSS and the regional Indian IRNSS.
You could probably cause a lot more trouble by buying an aviation radio off the shelf and just chatting on the frequency or issuing fake clearances if you want to be a mass murderer.
Ultimately the system comes down to many systems working together, not one stream of commands between two computers.
Incidentally, I am happily surprised that that never seems to happen. One could so easily create so much chaos at an airport... There is no authentication whatsoever.
I was flying once with a buddy of mine who was Pilot-In-Command and we lost (or thought we had lost) our radio on an IFR flight back into the Bay Area. What had happened was the Push-to-Talk button on the yoke had become stuck and we were transmitting the entire time while attempting to diagnose what was wrong. This happened for about five minutes. Thankfully he had a handheld radio in his flight bag, and when we turned it on we figured out really quickly what was going on.
In that scenario, if we didn't have the handheld radio, it would have caused a worse problem.
In the worst case, there are non-verbal methods of communication that pilots or ATC can employ (ATC can send light signals, pilots rock their wings to signal communication failures, etc.)
Every airplane between you and your destination, on the other hand, would find themselves being rerouted.
My point was that having the handheld radio allowed us to trouble shoot the situation. Without the radio there would have been a lot higher workload and less of a margin for safety.
The fact that no one has ever truly tried that sort of poisoning of radio calls is more due to the tower and aircraft having a very well defined set of calls, so that the likelihood of false transmissions being able to cause havoc is minimized already.
I agree with another commenter that aviation radio systems should be the simplest, most reliable systems possible, and have that layer of communication depend on proper radio call discipline and no more.
But what about cheap SBCs dropped somewhere with a battery and some custom periphery working as a relay? Of course the SUVs could find that. After the fact.
Problems happen when either (1) technology to do harm becomes commoditized and freely available so less capable people can acquire and use (eg. Easy conversion of semi automatic to automatics, commoditized hacks for script kiddies) or (2) capable people feel they're been sufficiently wronged that they don't care about the consequences of revenge (pretty much all the really big headline terrorist actions)
Most intelligence activity on prevention focuses on (2) since pulling off such actions generally requires the capable planners to coordinate with less capable "feet on the ground" who can give things away. However capable people acting alone which happens occasionally is pretty much impossible to stop (Timothy McVeigh, Ted Kazynski, Kaloyev)
It actually happened near me once when a local crazy guy got mad that planes were flying near his house (he bought a house right across the street from the municipal airport) so he found an airband radio and started yelling at them every time they came too close for his liking.
[1] https://www.youtube.com/watch?v=ZvA_-linhg8
He probably got lucky and had a station within 5-10 miles of his bathtub...
https://en.wikipedia.org/wiki/Toronto_Area_Control_Centre
It happens rarely, but pilots are also trained to not blindly follow clearances. They are still pilot in command.
Especially near major metro areas, unintentional interference is a daily issue. These systems immediately triangulate sources of interference in a wide band. Or you have simpler systems like UMS100 that just do alerting and you send out an engineer with a wand to walk around for a bit to triangulate it.
Add some fancy voice synthesis, and it gets interesting. The attacker could clone the voice and style of the air traffic controller. The attacker could provide enough power to quiet out any other transmissions. To keep the air traffic controller incompletely aware, the attacker could provide interference (just to the tower) whenever the victim aircraft begins to transmit.
Or are we talking about the boogieman that is an excuse for all sorts of paranoid crackdowns, expenditures, and questionable legislature?
Who exactly are you afraid will sponsor radio jammers at airports, and why do you think they will do so?
Just send the voice data through a raspberry pi to a remote location and carry out the attack from there. You could send voice data through a TOR-like protocol or something to keep you anonymous, if that's important. You could maybe rig some explosives to go off if the FBI/FCC/FAA gain access to the attack point, to prevent them from recovering evidence.
Lot's of police/fire radio systems are similarly without authentication, so you could amplify the mayhem by doing the same thing to those frequencies.
https://en.wikipedia.org/wiki/Airband
One of the reasons why airband radio uses amplitude modulation is so that a much more powerful transmitter (ground based, operated by air traffic control or tower personnel, with access to very high Tx powers), can transmit on top of spurious transmissions coming from low powered aircraft or handheld transmitters. The big ground based Tx can step on an interloper and communicate its message to all aircraft on the same frequency.
No they don't.
Most secondary (surveillance) radar in the US has been shut down already.
The FAA has been busy shutting down basically anything that requires maintenance, and LORAN is gone too.
I believe the whole point of ADS-B out was to shut down basically the rest.
Source: commercially-rated pilot.
Given that then ADS-B mandate was just a couple weeks ago, it seems logistically odd that secondary radar would already be turned off.
More generally, my understanding was that the FAA was keeping primary+secondary radar around to augment ADS-B via sensor fusion. I know the "reply" light on my plane's radar transponder still lights up regularly, so at least out here on the west coast the secondary radar is still active. :)
I've also heard there's a longer-term plan to consolidate ATC radar into the NOAA weather radar stations, once they upgrade weather radar to phased-arrays at some unknown point in the future. The marginal cost to keep secondary radar running in that environment is basically zero.
That said, they have certainly been turning down many of the redundant VOR stations as part of MON, and they just turned HIWAS off last week.
I don't think anyone really misses LORAN, though. ;)
I'd like to be wrong about this, but I'm not sure how I am. How am I potentially wrong about this?
It doesn't have to make sense.
https://en.wikipedia.org/wiki/VHF_omnidirectional_range
(Sorry, paywall is blocking me)
They've been reducing the number of redundant ground stations lately as part of a project called "Minimum Operational Network", or "MON". (Mostly on affecting the east coast.) But they're explicitly making sure there's enough coverage that you can get a VOR signal anywhere above 5,000 feet AGL.
More info: https://www.faa.gov/about/office_org/headquarters_offices/at...
I suspect VORs will be kept for airport locations and en route instructions, but most others will be shut down in favor of GPS.
From the FAA itself: "The Mode S SLEP Phase 2 program will implement modifications to the Mode S system to sustain secondary surveillance service through 2028."
0 - https://www.faa.gov/air_traffic/publications/cip/files/FY16-...
Maybe you're thinking of old-school SSR radars ?
[0] https://aviation.stackexchange.com/questions/43283/do-todays...
Article is pay-walled so I didn't read, but the title explicitly says 'from Radar to GPS', ie away from Radar altogether. It doesn't say, GPS to supplement radar.
ADS-B is not a guidance tool and will not lead to any more usage of GPS for guidance than is currently common - and certainly won't impact ILS. They're just totally different use-cases.
What do you mean by this? You sound pretty knowledgeable, so you must know that it's simply not possible for the GPS signal to have latency or lag.
The signals have to be received from each satellite, then processed to yield a position valid at the time of transmission.
Every GPS fix you get is delayed by AT LEAST that processing time. Any filtering adds more lag.
Most navigation systems look at the T(fix) -> T(now) difference and project your now position from the prior fixes. Especially if you're following driving directions as opposed to free movement, then programs like Maps etc project how much further you've moved on the route, not just along your velocity vector.
After a few seconds, though, that projection will stop moving, too, when the gap between last fix and now gets too large.
Lots of issues I'm sure. It'll be interesting to see how this sorts out.
> he’s seen truckers trying to avoid paying highway tolls, employees blocking their bosses from tracking their cars, high school kids using them to fly drones in a restricted area, and even, he believes, undercover police officers using them to avoid tails
These guys were doing it because they were tasked with keeping LTE towers synchronized and they did it with GPS time so they were building in resilience to their time sources by measuring the signal level and rejecting anything that came in too strong. Spotting jammers was a side benefit.
https://ipadpilotnews.com/2019/09/ads-b-traffic-when-does-it...
https://www.faa.gov/nextgen/programs/adsb/faq/#x8 You probably have a much large hole in your coverage than you thought.
https://www.youtube.com/watch?v=CXv1j3GbgLk
* https://en.wikipedia.org/wiki/Multilateration
* https://www.radartutorial.eu/02.basics/rp52.en.html
* http://www.multilateration.com/surveillance/multilateration....
This can further be cross checking with space-based systems like Nav Canada's:
* https://en.wikipedia.org/wiki/Aireon
Maybe if it's shown to be a great practical problem, they'll address it. If not, then no they won't. I'm guessing they won't.
It was my job to "help" with the navigation, using a paper chart and VOR/NDB steam gauge instruments. Dad was able to teach 10yo me how to do this stuff, but it was easy to confuse from/to or think you are tuned to station x when actually you are on Y, etc. Particularly night VFR was hard to be sure you were exactly where you thought you were. We did not fly over open water at night.
Later we got a primitive GPS, no maps just waypoints and lat/lng. That thing was so much easier to use it was night and day. Just dial in a 3 letter code for your airfield, and you get range,bearing,eta.
GPS is a huge improvement to safety and convince, but if it goes out a night or in bad weather there are gonna be some problems.
I've had kids ask me what we did before we had GPS and Google Maps and I tell them that we got lost or turned around a lot more often.
Even jamming near Nellis and Area 51 is done by NOTAM and not perpetual.
Maybe there is some permanent jamming somewhere but pilots would know about it as GPS availability knowledge is safety critical.
Almost all.
If you're flying VFR you can put your transponder into an anonymous / incognito mode (if it supports it):
* https://www.avweb.com/aviation-news/faa-acts-to-preserve-ads...
If you want IFR or flight following you'll have to de-anonymized, which is no worse than it was before ADS-B.
Does incognito mode in your browser stop you from being tracked if e.g Google or facebook can see every or almost all of your requests?
So people can see that someone is in a particular place, but not who that person/plane is.
I very much doubt that we'll get to even 80% of the fleet of FAA registered airplanes having ADS-B out by 2030. We're at about 50% right now.
https://www.faa.gov/nextgen/equipadsb/installation/current_e...
I feel like, for example, I'd be worried if fine-detail GPS data was being published live for example, or live enough to predict where the plane is "right" now...
https://flightaware.com/live/
Any time my dad takes his personal plane up for an hour's flight, I get a text message and can watch his track (and altitude/speed) in real-time.
The FAA in the US does publish a 'privacy list' of aircraft whose owners have requested that they not be included in services like this, and most commercial providers comply with that list, but enforcement is sparse and several hobbyist projects (e.g. ADS-B Exchange) do not and even emphasize aircraft that have put in such a request, since the tend to be a bit more interesting. A bit of a Streisand effect.
The same situation exists with the similar AIS system used by ships at sea, and has produced concerns over malicious use, but there continue to be plenty of websites that will show you maps of ship locations picked up by their contributing AIS receivers.
https://en.m.wikipedia.org/wiki/Tethered_Aerostat_Radar_Syst...
https://www.faa.gov/nextgen/equipadsb/research/airspace/
As you'll see from the various documentaries, historically planes operating illegally and/or doing illegal things will fly "under the radar" and keep their transponder turned off to evade the authorities.
They'll do the same thing with GPS.
Radar can be jammed too, but I would guess the EM signature powerful enough to track. I don't know if GPS jammers would have that issue.
On a positive note, I think this would pave the way towards integrating commercial drone infrastructure into our airways a lot better!
Most airplanes already rely heavily on GPS for their own navigation. If GPS is being jammed (or having any other clear issue) they'll fall back to their many other redundant navigation instruments.
If you want to be scared, be scared about spoofing of ILS signals, where a couple of dozen feet of error can be fatal.
https://arstechnica.com/information-technology/2019/05/the-r...
*all radar.
Certainly around airports radar will be kept, but there are a few (remote?) places where aging infrastructure will not be replaced.
On the plus side, there are areas that had no coverage (Gulf of Mexico) which now get traffic information from receivers that are easier to run than radar towers.
that's only a plus if you're not expecting malicious interference. how much harder is radar to spoof compared to GPS?
According to the crew on the USS Zumwalt they can make a 600' ship look as large as a cruise ship or as small as a fishing vessel. This ship is covered in radar absorbent materials and has a giant phased array to accomplish this.
EDIT: Apparently Loran C was discontinued in 2010.
[0]https://en.wikipedia.org/wiki/Loran-C [1] https://www.stripes.com/news/break-out-the-sextant-navy-teac...
What does "still maintain" mean in this context? My Loran-C receiver stopped working years ago when we turned off the signals.
https://en.wikipedia.org/wiki/Loran-C#Loran-C_in_the_21st_ce...
We still have it, and our commercial planes have been required to have ADS-B transponders here for more than a decade. This is just for en-route tracking.
Based on my experience, ATC Radar have no difficulty seeing commercial aircraft with a high probability of detection and low probability of false alarm.
Source: completed a performance assessment of several such systems in the early 2000s against their legacy counterparts using aircraft beacon systems as a source of “truth”.
If I remember to come back to this later, I’ll write a little post showing the theoretical detection performance of such a system. If you’d like to try the exercise yourself, the relevant worksheet is a Blake Chart and you can look up surrogate parameters for the Radar via checking the ASR-XX pages on Wikipedia (e.g. ASR-9 or ASR-11). Finding Radar cross sections (RCS) for commercial aircraft models is similarly straightforward. The system is logarithmic so as long as you’re in the ballpark you’ll be close.
The JSS is a descendant of the SAGE system developed during the Cold War to detect soviet aircraft. It has a reduced equipment footprint, but this is generally due to improving radar technology, coverage is similar and the backend data processing systems are much more advanced. The majority of radar sites belong to and are maintained by FAA but report directly to the Air Force air combat system.
[0] https://goo.gl/maps/KHTP7vruKvGyqQu66
[1] https://en.wikipedia.org/wiki/Joint_Surveillance_System
I'm not sure exactly what equipment is installed there, I found an older report listing an ASR-8 at that location but that system is obsolete and inconsistent with a newer list showing it as a secondary (SECRA) site only.
Consider that controllers currently rely primarily on secondary radar, which while more difficult to spoof than ADS-B is still quite subject to malicious manipulation. They are well aware that a primary radar return with no corresponding secondary radar information is something to sort out, and this won't change with a switch to ADS-B.
There is also flow control that is from the FAA — under IFR the acceptance rates are reduced.
The short answer isn’t that SFO isn’t “upgraded” but the rate of aircraft acceptance is reduced under low visibility conditions per the FAA — and for good reason, separation of aircraft.
Here is more explanation: https://media.flysfo.com/media/sfo/media/weather-operations-...
>GPS reception may be unavailable or unreliable over a large portion of the southeastern states and the Caribbean during offshore military exercises scheduled between January 16 and 24.
https://www.aopa.org/news-and-media/all-news/2020/january/14...
Considering that, I suspect the aviation industry will keep both systems working for a surprisingly long time.
If GPS were to become the sole way to do the latter, every airplane would effectively get an invisibility cloak that those who want to do evil can activate (and even worse. Switching off the on-board transmitter is less scary than spoofing signals)
Because of that, I would expect they keep using some way to detect planes that don’t tell them where they are, or radios broadcasting “plane P is at X,Y,Z” without a plane being there.
This is already the case. Much of the civilian radar system already relies on transponders to get a good fix on aircraft, via secondary radar. Primary radar coverage (no transponder required) is much more limited. Turn off the transponder and you'll largely disappear from ATC's screens.
ADS-B isn't new in this regard.
Yes, thank you for clarifying. I just explained that I am a pilot, so I did know that.
It was an analogy. Just like the way that pilots have multiple redundant "where are you tools", so too do I think traffic controllers will have multiple redundant "where is everyone" tools.
Because the industry, as a whole, is in favor of multiple redundant tools when it comes to safety.
Existing non-ADS-B based traffic management requires accurate altimeters and working transponders; we have always been at the mercy of systems that can fail. One of the many reasons for the substantial training of pilots.
On the plus side, lots of opportunity to create cockpit displays, warning devices etc to increase pilot safety!
So that's a good thing? interesting.
https://addons.mozilla.org/en-CA/firefox/addon/read-ft-wsj/
Not everything in life is free.
The Kessler syndrome is when collisions between objects cause a cascade in which each collision generates space debris that increases the likelihood of further collisions.
https://en.wikipedia.org/wiki/Kessler_syndrome
If you have an actual GPS app there's typically a diagnostic screen where can see where the satellites are and see them arrive and disappear from your perspective as they orbit.
(though i agree that kessler concerns are overblown.)
There's a legitimate concern that over-reliance on GPS will cause massive financial and loss of life damage in the civilian sector if it's ever denied through jamming or kinetic attacks or solar storm etc.
https://www.reuters.com/article/us-china-space-report/analys...
Global navigation constellations are certainly going to be one of the first targets in any major hot conflict between world powers.
Realistically, a solar storm is a more likely and less predictable threat. The end result is the same, any critical functionality that relies on GPS will be denied for a prolonged period of time.
Do you have a cite for this?
Other thing I completely forgot to mention is that all existing global navigation constellations orbit at MEO, not GEO. Which puts them within speculative range of demonstrated ASAT weapons and allows for even longer reach from a launch vehicle like LGM-30.
https://www.mda.mil/news/11news0002.html
https://www.raytheon.com/capabilities/products/ekv
This doesn't make sense to me. Could you explain further? LGM-30 is a land-based ICBM designed to strike targets on the surface of the Earth, and hence to take a (just barely) sub-orbital trajectory <13,000 km from point-to-point, with maximum altitude a few hundred km. Wouldn't its thrust capability have to be drastically upgraded to reach 20,000km in altitude, where MEO satellites like GPS are?
A derivative of the LGM-30, Minotaur, is used to launch satellites (or ordnance) directly to GTO @ ~30,000km.
GPS satellites will not have the hardware to do selective availability in GPS III, which are currently being launched:
* https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...
ADS-B doesn't change anything about how a plane navigates. That's still done with a plethora of redundant instruments, all working together.
[1] https://www.gps.gov/systems/gps/modernization/sa/faq/#on [2] https://archive.defense.gov/releases/release.aspx?releaseid=...
But if SA was enabled:
Before it was turned off on May 2, 2000, typical SA errors were about 50 m (164 ft) horizontally and about 100 m (328 ft) vertically
https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...
[1] https://www.skybrary.aero/index.php/Ground_Based_Augmentatio...