Norad

[PhantomWolf]

Interesting, but I could have sworn I've seen somewhere that the RADAR system that feeds NEADS/NORAD is pointed outward, not inward...

Does NEADS have a way of correlating altitude information to civilian ATC tracks who are not getting secondary (interrogation) return?

The do, but they use the FAA sites base about the coastal areas which means they cover areas inland along the East and West Coasts, they just usually ignore it and concentrate on the Ocean areas.

T be honest I have no idea if they can determine Altitude or not. Probably not. This was likely the reason to suggest and sent up planes to intercept, so they'd have the information on where the plane was. I'm sure Cheap Shot could fill in the blanks a lot better here.

 

[Ivan The Song Boy]

They weren't below 10,000 feet until they were into the ground clutter though, and as noted above, the FAA knew where 3 of them were throughout their entire flight so they didn't have to pick them out. Also planes on Pimary radar don't have Alttiudes attached, that is a function of the Secondary Radar, which they lost in 2 cases. NORAD of course had none of that information to start with, they just had 1-2000 dots moving on the screen, plus additional ground clutter.

Indeed. Understood. I was just pointing out that it would be easy to eliminate many other aircraft that were primary only, because they would all be slow, and low compared to the Criminal aircraft. In other words, as primary targets go, it seems that a fast jet would stick out among them, even though we would not know its altitude.

Ivan......................

 

[Cheap Shot]

The do, but they use the FAA sites base about the coastal areas which means they cover areas inland along the East and West Coasts, they just usually ignore it and concentrate on the Ocean areas.

T be honest I have no idea if they can determine Altitude or not. Probably not. This was likely the reason to suggest and sent up planes to intercept, so they'd have the information on where the plane was. I'm sure Cheap Shot could fill in the blanks a lot better here.

Finding the altitude using the ARSR-4 is nothing more than traingulation. The FAA never felt they had a need for that part of the system. It passes through our buildings but we don't do anything with that data. The military does use the height finding portion. We actually could have brought the info up on a PC which I found out later. But we were originally trying to find out the altitude of AAL11. The system isn't that accurate but it could give you an altitude within 3,000 ft below or above the target. But they could never see the target so we never got the info we were looking for. UAL175 switched its transponder to a different code, so it was still being tracked. And as said before AAL77 was in a secondary area only. Switching to Primary on the FAA display shows up as a digitized plus + symbol. If it is very small it will show up as a dot. You can track the plus + symbol and when it is being tracked susch as ALL11 the plus + symbol tirns into an X.

NEADS used the radar inside the US as well not always over the ocean, when they provide service as an MRU military radar unit. They provide GCI service to fighter aircraft operating in MOAs and ATCAAs.

 

[JoeyDonuts]

I'm genuinely curious here, CheapShot. I'm mostly familiar with the triangulation of surface tracks from passive receivers, and sometimes correlating with surface search radar.

How does one triangulate altitude from a radar that only gives you azimuth and range? I apologize if I've missed something here, I'm a tad out of my element.

EDIT: Actually...disregard. I think I did, in fact miss something.

 

[PhantomWolf]

Indeed. Understood. I was just pointing out that it would be easy to eliminate many other aircraft that were primary only, because they would all be slow, and low compared to the Criminal aircraft. In other words, as primary targets go, it seems that a fast jet would stick out among them, even though we would not know its altitude.

Ivan......................

None of the jets were travelling at speeds greater than any other aircraft at altitude. The speed factor came in once they dropped in altitude to head at their targets, but previous to that they were all under Autopilot control. The Hijackers seem to have merely changed the destination and allowed the planes to do most of the flying, taking over to hit the targets once they had them in sight. Even so their speeds at impact weren't excessive for planes at cruise altitude, just for planes at low altitude.

 

[gumboot]

FAA Radars

ARSR-1E
The Air Route Surveillance Radar Model 1E (ARSR-1E) is based on a 1970s vintage radar that has been updated through Service Life Extension Program (SLEP). It is a long-range radar system with a maximum detection range of 200 nautical miles (nmi). The ARSR-1E is a surveillance system used to detect azimuth and slant range of en route aircraft operating between terminal areas. It also provides weather intensity data. ARSR-1 and ARSR-1D are similar configurations to the ARSR-1E. The ARSR-1E is interface to a collocated Common Digitizer Model 1/2 (CD-1/CD-2) or other digital processor which provides digitized output.
The ARSR-1E is integrated with a collocated ATCBI-6 or Mode S beacon to provide correlated target output data. Twenty-two ARSR-1E systems are collocated with ATCBI-6 and three are collocated with Mode S systems.
These are legacy FAA and DOD systems that are now owned by DOD. The FAA will participate in maintenance and staffing. These systems are likely to be replaced by DOD if decommissioned.

ARSR-2
The Air Route Surveillance Radar Model 2 (ARSR-2) is based on a 1970s vintage radar that has been updated through Service Life Extension Program (SLEP). It is a long-range radar system with a maximum detection range of 200 nautical miles (nmi). The ARSR-2 is a surveillance system used to detect azimuth and slant range of en route aircraft operating between terminal areas. It also provides weather intensity data. The ARSR-2 is interface to a collocated Common Digitizer Model 1/2 (CD-1/2) or other digital processor which provides digitized output.
The ARSR-2 is integrated with a collocated ATCBI-6 and Mode S beacon to provide correlated target output data. Eighteen ARSR-2 radars provide service to the NAS. These systems are owned by DOD with maintenance support from the FAA. The ARSR-2 service will be sustained until 2025.

ARSR-3
The Air Route Surveillance Radar Model 3 (ARSR-3) is a 1980s radar that provides primary long-range surveillance data, including slant range and azimuth data. It processes the returns which includes demodulation, analog-to-digital conversion, moving target indicator (MTI) function processing, sensitivity time control (STC), range and azimuth gating (RAG), and digital target extraction - all of which are performed digitally (with the exception of the front-end RF demodulation and analog-to-digital conversion). In addition, the ARSR-3 has a weather channel with associated processing to provide three-level weather intensity contour information in digital format.
Twelve ARSR-3 systems are integrated with a collocated ATCBI-6 or ATCBI-5 beacon system to provide correlated target output data. Primary radar service in the affected coverage areas will be sustained until 2027 by DOD unless a decision is made to replace them with new surveillance systems. The FAA will provide maintenance support.

ARSR-4
The Air Route Surveillance Radar Model 4 (ARSR-4) is a three-dimensional, long-range, rotating phased array, primary surveillance radar with integrated height finder capability. It is part of the Joint Surveillance System (JSS) that is used in conjunction with ARSR-1, ARSR-2 and ARSR-3, to provide coverage as part of the National Airspace System (NAS) and nationwide air defense surveillance network. The ARSR-4 performs the functions as other ARSR radars for the FAA. ARSR-4 also satisfies DOD specific requirements for providing height data on surveillance targets. The ARSR-4 outputs weather intensity contour data formatted in up to six levels of intensity.
The ARSR-4 is integrated with a collocated Air Traffic Control Beacon Interrogator Model 5 (ATCBI-5) or ATCBI-6 beacon systems to provide correlated target output data. ARSR-4 is not currently collocated with Mode Select (Mode S) systems.
Forty-one (41) ARSR-4 systems provide service to the NAS. Two additional systems are owned by DOD and do not interface to the NAS. One support system is installed at the FAA Logictics Center. ARSR-4 systems are funded by DOD and FAA with providing FAA maintenance support. Plans are to sustain the ARSR-4 up to 2025 unless a decision is made to procure replacement systems through DOD earlier.

Taken from the FAA's NAS Architecture 6

 

[JoeyDonuts]

ARSR-4
The Air Route Surveillance Radar Model 4 (ARSR-4) is a three-dimensional, long-range, rotating phased array, primary surveillance radar with integrated height finder capability.
<snip>
The ARSR-4 performs the functions as other ARSR radars for the FAA. ARSR-4also satisfies DOD specific requirements for providing height data on surveillance targets.

That's what I was looking for.

I think I can finally wrap my brain around it now. Thanks, kiwi.

 

[Cheap Shot]

What He Said

For Joey Doughnuts, What Gumboot said.

For Gumboot any data on the FAA ATRCRBS do they show it as part of thier future plans, this is what the FAA wanted to go to prior to 9-11 no primary radar, beacon only. We have a site up in Skowhegan, ME.

 

[gumboot]

For Joey Doughnuts, What Gumboot said.

For Gumboot any data on the FAA ATRCRBS do they show it as part of thier future plans, this is what the FAA wanted to go to prior to 9-11 no primary radar, beacon only. We have a site up in Skowhegan, ME.

I think the plan post 9/11 is that DOD will maintain all primary radars and procure replacements as necessary.