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Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

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Re: Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

#81

Post by jessriedel »

akiselev wrote: post #75
GnarfGnarf wrote: post #72

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. https://en.wikipedia.org/wiki/Kessler_syndrome

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.

Re: Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

#82

Post by jessriedel »

missosoup wrote: post #78
akiselev wrote: post #75

Earlier quoted context omitted.

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.

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.

https://www.reuters.com/article/us-china-space-report/analys...

Re: Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

#83

Post by voxl »

qrbLPHiKpiux wrote: post #79
FabHK wrote: post #76

Earlier quoted context omitted.

> 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.

But the risks and consequences are catastrophic. The Feds will put you away forever for even attempting it.

While true, you'd think state sponsored terrorism wouldn't care about sacrificing a few people.

Re: Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

#84

Post by derstander »

ufmace wrote: post #74

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 al…

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.

Re: Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

#85

Post by missosoup »

jessriedel wrote: post #82
missosoup wrote: post #78

Earlier quoted context omitted.

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. https://www.reuters.com/article/us-china-space-report/analys...

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.

Re: Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

#86

Post by gruez »

freeone3000 wrote: post #43
gruez wrote: post #28

Earlier quoted context omitted.

>GPS is actually reserved, so there's going to be a lot less accidental interference. that's only a plus if you're not expecting malicious interference . how much harder is radar to spoof compared to GPS?

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.

Re: Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

#87

Post by AWildC182 »

FabHK wrote: post #76
jrockway wrote: post #67

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 rada…

> 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.

It happens sometimes [1]

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

Re: Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

#88

Post by TkTech »

qrbLPHiKpiux wrote: post #79
FabHK wrote: post #76

Earlier quoted context omitted.

> 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.

But the risks and consequences are catastrophic. The Feds will put you away forever for even attempting it.

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.

Re: Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

#89

Post by jcrawfordor »

ufmace wrote: post #74

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 al…

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.

Re: Air-Traffic Control Is in the Midst of a Major Change from Radar to GPS

#90

Post by lozaning »

sgc wrote: post #73
jellicle wrote: post #40

Earlier quoted context omitted.

Drug smuggling planes might not be in full compliance with every single regulation.

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?
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