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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 di

by ufmace 7y ago

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.

derstander 7y ago
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.
jcrawfordor 7y ago
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.
- ufmace 7y ago
  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.
  - jcrawfordor 7y ago
    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.
    - briandear 7y ago
      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.
- jessaustin 7y ago
  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]. [0] https://goo.gl/maps/KHTP7vruKvGyqQu66 https://goo.gl/maps/KHTP7vruKvGyqQu66 [1] https://en.wikipedia.org/wiki/Joint_Surveillance_System https://en.wikipedia.org/wiki/Joint_Surveillance_System

by ufmace 7y ago

derstander 7y ago

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.

jcrawfordor 7y ago

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.

ufmace 7y ago
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.
- jcrawfordor 7y ago
  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.
  - briandear 7y ago
    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.
jessaustin 7y ago
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]. [0] https://goo.gl/maps/KHTP7vruKvGyqQu66 https://goo.gl/maps/KHTP7vruKvGyqQu66 [1] https://en.wikipedia.org/wiki/Joint_Surveillance_System https://en.wikipedia.org/wiki/Joint_Surveillance_System