propilot83
Posts: 618
Joined: Sat Jan 27, 2001 2:41 am

Ocean Radar Coverage

Sat Sep 12, 2009 8:48 am

I know that NORAD can track any plane, missile, etc. NOT only over North America, but all over the entire globe. I know that the FAA Command Center in Virginia tracks all flights over the U.S. and possibly North America. My question is, flights that are inbound and outbound over the Pacific, Indian, Atlantic Ocean, and Polar Routes who keeps an eye on them? Is there some kind of agency or is there some kind of command center that keeps radar tracks of flights over the Oceans so some one has an eye on everyone? I mean theres got to be something out there over the ocean or some country that keeps a radar track on flights over the Pacific, Atlantic, and Indian ocean? What if there is a thunderstorm in the middle of the ocean and many flights have to be diverted on another route, who can give that command? Where does the command or authority to divert come from? I am sure pilots cant just make their own decisions just because they have TCAS! Anyone know anything? Thanks!
 
MrChips
Posts: 933
Joined: Wed Mar 30, 2005 2:56 pm

RE: Ocean Radar Coverage

Sat Sep 12, 2009 9:38 am



Quoting Propilot83 (Thread starter):
I know that NORAD can track any plane, missile, etc. NOT only over North America, but all over the entire globe.

That's not entirely true. Missiles are detected and tracked by satellite (using the infrared emitted from the exhaust plume) initially and by radar in later stages of flight. Now, missiles fly much higher than aircraft do (reaching an apogee of several hundred miles in some cases), making it possible to detect a missile on radar hundreds or even thousands of miles away from the station. Aircraft are a different story; because they fly much lower than a missile does, they are only detectable for a couple of hundred miles at the most.

Quoting Propilot83 (Thread starter):
flights that are inbound and outbound over the Pacific, Indian, Atlantic Ocean, and Polar Routes who keeps an eye on them? Is there some kind of agency or is there some kind of command center that keeps radar tracks of flights over the Oceans so some one has an eye on everyone?

Oceanic control centers monitor transoceanic flights. Basically, they function as an extension of the domestic area control centers of most countries. And they have very limited radar coverage - once the aircraft is over the horizon, there is no more radar coverage. Beyond that, position reports and flight plans are fed into a computer (or onto a big map in some cases), with an approximate position be determined from that. The thing you need to remember is that despite the volume of traffic, oceanic airspace is essentially uncontrolled airspace.

Quoting Propilot83 (Thread starter):
What if there is a thunderstorm in the middle of the ocean and many flights have to be diverted on another route, who can give that command? Where does the command or authority to divert come from? I am sure pilots cant just make their own decisions just because they have TCAS!

Pilots have eyes, remember, and thunderstorms are easy to spot, both visually and with weather radar. If something does come up, they will make a call to the oceanic control center to figure out if their planned course of action is possible (often, aircraft will divert from one track to another, fly an offset distance from a track, or will climb or descend to avoid the phenomenon - oceanic control will be able to tell them if there is enough "room" on another track or altitude for them to do so).

On the topic of weather, things tend not to just "pop up" locally over water as they do over land - the open ocean can be considered, at least when compared to land, to be very close to uniform in terms of surface features and available energy. As such, weather systems tend to develop over much larger areas, but do so in a much more predictable manner. Because of this, it is possible (to an extent) to route nearly all flights around most of the hazardous weather that is forecast.

Quoting Propilot83 (Thread starter):
Anyone know anything?

No, nobody knows anything.  sarcastic  Please use precise English.
Time...to un-pimp...ze auto!
 
jgarrido
Posts: 258
Joined: Thu Mar 08, 2007 4:40 pm

RE: Ocean Radar Coverage

Sat Sep 12, 2009 10:15 am



Quoting MrChips (Reply 1):
The thing you need to remember is that despite the volume of traffic, oceanic airspace is essentially uncontrolled airspace.

Perhaps you were generalizing, but technically speaking this isn't really accurate. In the Pacific the floor of PCA (positive control airspace, aka Class A) is 5500'. Domestically it's FL180. There are a few exceptions to this rule, but still the majority of the airspace is not uncontrolled (Class G).

Quoting Propilot83 (Thread starter):
What if there is a thunderstorm in the middle of the ocean and many flights have to be diverted on another route, who can give that command? Where does the command or authority to divert come from? I am sure pilots cant just make their own decisions just because they have TCAS! Anyone know anything? Thanks!

As MrChips mentioned there are ATC facilities which are designated responsibility for different areas of oceanic airspace. Airliners flying across the ocean are not on their own. There is still a controller somewhere who has the responsibility to keep the aircraft separated. Because of that aircraft must still receiver permission to deviate/climb/descent/etc. just like they do if they are in radar control. Even though there is no largely not radar coverage, there are nonradar procedures which controllers use to separate the aircraft. These procedures largely rely on position reports and time estimates so there is quite a bit of extra separation built in.
 
CosmicCruiser
Posts: 2049
Joined: Tue Feb 22, 2005 3:01 am

RE: Ocean Radar Coverage

Sat Sep 12, 2009 1:05 pm



Quoting Propilot83 (Thread starter):
I am sure pilots cant just make their own decisions just because they have TCAS! Anyone know anything? Thanks!

First you would never make a decision based on the fact that you have TCAS. TCAS is a wonderful tool and can be a lifesaver but I would never navigate into any airspace planning on TCAS saving my butt.
There are controlling agencies eg Gander/ Shanwick that do monitor and control traffic though it's done alike the old days "blindly". That's the reason for a constant mach clearance. With more and more a/c having ADS/CPDLC the controllers have more accurate and timely info and communication is easier than the old HF days. As for wx avoidance first contact the controller and make your request for a deviation. Usually it's no problem. If there's a delay in response you just do what you have to do. A couple of months ago i was flying to SIN over the China Sea and a wx deviation became necassary. We sent a CPDLC msg but received no reply. Finally I made a turn to avoid the cell and sent another msg saying we were deviating xx miles east for wx. Finally we got a reply saying approved. No problem. I've got a photo of that TRW as we passed by that maybe I'll try to post here later. must go now.
 
cobra27
Posts: 939
Joined: Wed May 23, 2001 6:57 pm

RE: Ocean Radar Coverage

Sat Sep 12, 2009 3:51 pm

NAT (North Atlantic Airspace) is quite heavily regulated. Google this acronyms RVSMP, NATS, OTS,MNPS - they made thousand new acronyms when they established NAT (some acronyms even include acronymes nthemselves)
You can find more on NAT on ATPL book Air Law. >But generally it is quite safe place to be. Only long range jets. Mostly airliners, bussiness jet ussually take southern route which are longer.
 
ThirtyEcho
Posts: 1409
Joined: Tue Jan 01, 2002 1:21 am

RE: Ocean Radar Coverage

Sun Sep 13, 2009 8:17 am

Surprisingly enough, ATC functioned pretty well from the 1930s to the late 1950s without radar. The first time that I ever had "radar contact" was in 1960 via Dallas Approach Control. There were no transponders; in order for the controller to identify you, you had to make a turn to a prescribed heading assigned by the controller.
 
meristem
Posts: 53
Joined: Wed Jun 03, 2009 4:50 pm

RE: Ocean Radar Coverage

Sun Sep 13, 2009 5:45 pm

Propilot83,
Due to Earth's curvature, complete oceanic coverage (without any hack such as utilizing several communication methods to draw a layered understanding of where an aircraft is) would most likely rely on a geostationary satellite grid. The total cost of ownership and the political corollaries of building such system are significant. HOWEVER, the internet and GPS development indicate paths for such implementation.
Curiosity killed that cat. I still have some lives left.
 
MD11Engineer
Posts: 13916
Joined: Sun Oct 26, 2003 5:25 am

RE: Ocean Radar Coverage

Sun Sep 13, 2009 6:26 pm

There exist over-the-horizon radar systems for military use, but since they operate in the HF range (instead of the VHF range and higher as for conventional radars), the resolution is quite poor. They basically only deliver an early warning that something is coming, but can´t give accurate directional and altitude information (very similar to the Chain Home High radar systems used by the Brits during WW2, which also were operating in the HF range).
HF gets reflected (under certain conditiomns depending on the wavbe length and the ionisation of the upper atmoshere, which again depends on solar activity) by ionised layers in the upper atmosphere and can therefore follow the curvature of the aerth. On the other hand the wave lengths used are in the same size range or bigger than aircraft (10 -80 meters), therefore the resolution is poor.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
propilot83
Posts: 618
Joined: Sat Jan 27, 2001 2:41 am

RE: Ocean Radar Coverage

Mon Sep 14, 2009 5:38 am

Thank you very much everyone for providing great understanding information to my question in detail. I will now conduct a further review of the information provided.
 
Woodreau
Posts: 1182
Joined: Mon Sep 24, 2001 6:44 am

RE: Ocean Radar Coverage

Wed Sep 16, 2009 5:15 am



Quoting Propilot83 (Thread starter):
I know that NORAD can track any plane, missile, etc. NOT only over North America, but all over the entire globe.

That is definitely not true - radar is not "ALL knowing" and even if you do have radar, it doesn't guarantee that you see everything in the sky.

There are command centers that have a "fusion" plot or something that the military calls a common operational picture which is a track database that is pictorially displayed on a global map kind of like a flight tracker display. But it is not real-time and it depends very heavily on reporting radar units updating their tracks regularly (or not.) Once of the things you have to check when you look at these fusion plots is to see how old that track is (it may be several hours or several days old) - garbage in - garbage out.

So if you are in one of those command centers and happen to see all the radar contact over the whole globe - it is a compiled picture from US and allied friendly forces all over the world - but someone has to be there to see it. kind of like if a tree falls in the middle of a forest and no one is there to hear it - does it make a noise?

Then again there may be radar coverage in the middle of an ocean, i.e. from a transiting warship. However, that warship is not reporting its radar tracks to any air traffic control agency and so only that ship and task force know what aircraft are out there. By the same token, the warship/task force have no ATC information either so they know that the aircraft they are seeing are following a NAT track or one of the R tracks between the US west coast and Hawaii, they have no idea what flight number it is other than it is squawking a specific transponder code and they know it's altitude, and the warship derives the aircraft's course and speed over tracking the aircraft over time (it only takes a few seconds).

Once you get 100-200 miles offshore, you won't have radar coverage and so I imagine ATC separates aircraft procedurally with position reports by time/speed, lateral, and vertical seperation rather than using radar.

Since there is no radar coverage offshore, one of the first things that happened after 9/11 (among other things), was the Navy sortied out to sea and assumed radar picket stations all around the US seaboard, and uploaded their radar tracks to the 3 US NORAD Air Defense Sectors (WADS, NEADS, SEADS) through the track database I mentioned earlier - in essence temporarily extending NORAD's radar coverage out to sea.

There is a lot of radar theory in MD11Engineer's post. generally the longer ranged the radar, the poorer the resolution, bearing suffers more than range. The AEW radars on the E-3 Sentrys and E-2 Hawkeyes are great for seeing that there is something out there. I imagine that the E-3's radars are much better than the E-2's who's comments about their radar picture is "Yep, there are angry bananas out there." referring to the appearance of the radar contacts on the extreme range of the radar scope (since the bearing resolution is so poor, the radar contact is "stretched out" looking like a banana with the detected contact being somewhere on say on the 045 to 050 bearing (for example) which at 240 miles, 5 degrees of bearing ambiguity equates to about a 20 mile position error.

Missiles are actually harder to see than aircraft - (the anti-ship ones that I care about anyways) Their altitude is lower than helicopters and my detection range against them is less than (let's just say) 20 miles - and that is if I know they're coming.
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
Caryjack
Posts: 312
Joined: Tue May 08, 2007 9:45 am

RE: Ocean Radar Coverage

Sat Oct 17, 2009 6:12 am



Quoting MD11Engineer (Reply 7):
There exist over-the-horizon radar systems for military use, but since they operate in the HF range (instead of the VHF range and higher as for conventional radars), the resolution is quite poor.

Interesting post.  scratchchin  Ive read of an HF communications system called "over-the-horizon tropospheric scatter" but this is the first I've heard of a radar system operating in about the same manner. I understand the poor resolution and I would also think that reliably recovering a reflected signal could be a problem. It seems like it would squawk "Here I am, where are you?" laughing 

Quoting Woodreau (Reply 9):
if a tree falls in the middle of a forest and no one is there to hear it - does it make a noise?

It made a noise, but not a sound was heard. wink 
Thanks, smile 
Cary
 
MD11Engineer
Posts: 13916
Joined: Sun Oct 26, 2003 5:25 am

RE: Ocean Radar Coverage

Tue Oct 20, 2009 12:02 am



Quoting Caryjack (Reply 10):
Quoting MD11Engineer (Reply 7):
There exist over-the-horizon radar systems for military use, but since they operate in the HF range (instead of the VHF range and higher as for conventional radars), the resolution is quite poor.

Interesting post. scratchchin Ive read of an HF communications system called "over-the-horizon tropospheric scatter" but this is the first I've heard of a radar system operating in about the same manner. I understand the poor resolution and I would also think that reliably recovering a reflected signal could be a problem. It seems like it would squawk "Here I am, where are you?" laughing

Tropospheric scatter is more of a VHF / UHF thing (especially in summer months during high solar activity you´ll get a condition called "sporadic E", in which cells of air in the higher troposphere get ionised enough by the sun light to reflect radio waves in the upper HF range (20-30MHz) or VHF/UHF range. This allows the radio waves, which normally would only travel line of sight to get behind the horizon. Thunderstorm fronts and aurora borealis have a similar effect, though due to their own electrical activity they often disturb the signal beyond recognition.

HF gets reflected at layers in the very upper atmosphere (about 150 to 200 km), in the ionosphere or "Heavyside layer", as it was called first after it´s discoverer.
Newerresearch has shown that this layer actually consists of 2-3 different layers. The lowest one, the "D" layer, has a dampening effect on lower frequency HF (3-10 MHz), so that these frequencies can only reach long range at nightime, when solar radiation is low and the concentration of ions in this layers decreases.
The two higher layers F1 and F2 actually reflect HF, the higher the ion concentration is the better (summer, daylight). Therefore longrange propogation of higher frequency HF (10-30 MHz) is best during summer and daylight. Lower frequency HF (3-10MHz) and medium waves get attenuated too much during daytime and summer, so that during daytime you can only receive the shortrange ground wave (which follows the ground for a few hundred km) and not the long range sky wave, which gets bounced back and forth between the ionosphere and the ground.

Jan
Je Suis Charlie et je suis Ahmet aussi

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