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Worldwide (space based) tracking of ADS-B aircraft coming, over Iridium (Aireon etc)

here

This is the result of MH370 – except that somebody in the cockpit turned off ADS-B, as well as Mode S (or they both failed at the same time…).

I guess Iridium will be announcing a new low speed data link – 1200 baud – to replace its present high speed data link of 2400 baud

The interesting Q is where will the data be distributed. If it is available online, then every airport tower could use it as an unofficial radar feed. Of course, in GA, almost nobody is radiating ADS-B, but this may drive regs to change that – for IFR, or for VFR in some airspaces.

Administrator
Shoreham EGKA, United Kingdom

The background of ADS-B tracking from space can be found here and here.

So the interesting question is what’s the use of this?

From the article, it seems that this works only on LEO (or “VLEO”) satellites and then just barely. If you wanted to cover the whole earth surface, you’d need at least 800 space vehicles (the article gives 600000km^2 as antenna footprint; likely you’d need a lot more than 800 SVs because most SVs would be close to the poles at any given time). Nobody is going to finance that.

So either my fantasy is too limited, or this is a solution in search of a problem.

LSZK, Switzerland

So the interesting question is what’s the use of this?

I guess to reduce the need for ground based radar coverage, especially over sea and sparsely populated ares.

EDDS - Stuttgart

So the interesting question is what’s the use of this?

Nobody is going to finance that

This is a solution in search of a problem

I think everybody is aware of the long term automated taxation possibilities. Obviously that would provide a return on investment.

Last Edited by Silvaire at 22 Feb 18:15

The interesting Q is where will the data be distributed.

I am quite afraid the answer is obvious: the information will be disclosed to any( )body willing to pay sufficiently. Welcome to the 21st century!

EBZH Kiewit, Belgium

I guess to reduce the need for ground based radar coverage, especially over sea and sparsely populated ares.

But how are you going to do this? 70% of the surface is water, so you still need 600 or more space vehicles. Unless you’re happy with 1 position report every hour.

I still don’t see what this gives you over existing solutions, such as ACARS over Satcom.

I think everybody is aware of the long term automated taxation possibilities.

In order to realize a system like this, you need taxation in a big way to get it started Remember Iridium? It was and still is a massive commercial failure, and it requires less than one tenth the number of space vehicles. It only still exists because the DoD keeps it alive.

LSZK, Switzerland

I only skim-read that article but my understanding is that they will use some sort of spare bandwidth on the existing Iridium satellites to receive the ADS-B packets.

It can also be done with just a few geosynchronous satellites. After all, the NSA can listen to any cellular or satphone phone call from those – though admittedly they are pretty expensive.

ACARS over satcom (over Immarsat usually) is not as cheap as the airlines would like it to be. So many turn off ACARS once out of VHF range. I would think continuous position reporting over Iridium would be great if you are an Immarsat shareholder but the airlines would not want to pay for it. But didn’t Immarsat offer free handling of ADS-B (or ADS-C?)?

But to prevent another MH370 disappearing (you cannot actually prevent what I think happened in the cockpit) they will also need to modify the systems so the pilot cannot turn the stuff off.

Administrator
Shoreham EGKA, United Kingdom

It can also be done with just a few geosynchronous satellites.

Achim’s article essentially claims that this would lack in link budget.

I only skim-read that article but my understanding is that they will use some sort of spare bandwidth on the existing Iridium satellites to receive the ADS-B packets.

I very much doubt this. The normal frequency of operation of the Iridium satellites is around 1.6GHz, so the antennae and receivers wouldn’t work on 1090. This suggests that they put extra hardware on the satellites.

ACARS over satcom (over Immarsat usually) is not as cheap as the airlines would like it to be.

Yeah airlines always want everything for free and then some, but the question is whether this aireon thing will be cheaper in the long run. I don’t see anything fundamental to make it cheaper. Also, it only solves half of the equation. If you want to separate more tightly, you also need a channel to issue (re)clearances. How do you do that? HF is too unreliable and too low bandwidth. So you still need Satcom.

If they really wanted to save and increase capacity massively, they should just drop the attempt at air traffic control from the land. Just require anyone who wants to cross the atlantic to be equipped with 1090ES ADS-B out and in, with a set of rules on minimum distance and who needs to give way etc.

LSZK, Switzerland

This project was originally driven by Canadian ATC (NAV Canada) who don’t have radar coverage over huge parts of their landmass. The commercial organisation Aireon was setup as a joint venture with Iridium to market the traffic information captured by special hardware fitted to the newest generation Iridium satellites and relay that to any ATC that wants it (for a fee). This can include oceanic coverage too if there’s a market for it. The Australians are also pretty interested. NAV Canada already use ADS-B extensively to reduce separation on transatlantic flights.

The newer generation Iridium NEXT satellites will have greater transmission bandwidth and this additional ADS-B receiver built in. It won’t transmit ADS-B, just capture any signals in their footprint and relay them. Not to be confused with current Iridium two-way system. Aireon is planned to be live globally by 2018.

However, I’d agree it still doesn’t stop a pilot turning off their ADS-B transponder (e.g. if it was on fire) and going silent. Perhaps it might just be noticed a bit quicker.

Can’t see this being relevant to GA apart from the odd transatlantic flight or other very remote location. SPOT trackers are probably more appropriate.

FlyerDavidUK, PPL & IR Instructor
EGBJ, United Kingdom
35 Posts
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