ADS-B via satellite

Sounds like a receive-only system which will not provide the broadcast features we're discussing. But it would be a step in the right direction, and piggy-backing broadcast of weather and traffic shouldn't be a major technological hurdle (although cost might be another story).
 
Inmarsat already provides this service via ACARS sat link. But not to ATC but company. MH370 was equipped with this but it was turned off intentionally. I do not see how it would had been any better with Iridium. After all MH370 was under ATC radar surveillance until someone turned off the transponder.

José
 
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I was not aiming this post at anything to do with MH370.
 
Ron Levy said:
Sounds like a receive-only system which will not provide the broadcast features we're discussing. But it would be a step in the right direction, and piggy-backing broadcast of weather and traffic shouldn't be a major technological hurdle (although cost might be another story).
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Well, sure it does not provide weather or traffic uplink, but it could give ATC "radar" coverage from the ground up over the entire planet.
 
As far as cost, how much did the FAA spend installing hundreds of ADS-B towers across the country?

I'd think 1-2 satellites would be on par with what was spent.
 
I started writing a freaking essay on the topic why using GEO for mobile M2M comms is dumb, but it's late and anyhow, it should be obvious. Sats are too far, you need a high-gain antenna, etc. etc. And yes I know that AIS has a GEO segment with the same Inmarsat.

The best part of LEO is actually that sats might be able to pick the existing 1090ES or even UAT with good enough resolution for useful tracking. GEO can't do that, so you mandate separate set of equipment. Even today people are not happy about meeting the 2020 mandate. On my airplane there's literally no spare payload for a 2.5 lbs Trig transponder, even if I had extra $5k. Sticking every spam can with an Inmarsat terminal? I don't think it's going to fly (pardon the pun).
 
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There's also already a number of commercial sats offering tracking services and others that can do it very easily.
 
denverpilot said:
There's also already a number of commercial sats offering tracking services and others that can do it very easily.
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True, but if everyone is required to have ADS-B by 2020 and it is an international standard, why not use it?
 
dans2992 said:
True, but if everyone is required to have ADS-B by 2020 and it is an international standard, why not use it?
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one reason to not use it: the flaws of ADS-B out (no validation of messages)
 
Piloto said:
Inmarsat already provides this service via ACARS sat link. But not to ATC but company. MH370 was equipped with this but it was turned off intentionally. I do not see how it would had been any better with Iridium. After all MH370 was under ATC radar surveillance until someone turned off the transponder.

José
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How do you know those items were "intentionally" turned off ? All we know for sure is that power was removed, by what method remains to be seen.
 
Bob Noel said:
one reason to not use it: the flaws of ADS-B out (no validation of messages)
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That is true. But an ADS-B out transponder is just a conventional Mode S transponder with Mode C capability also. The position reported on ADS-B out can be easily correlated with a Mode C interrogation by an ATC radar.

There is also the multilateration surveillance method were traffic position is determined by the TOA (time of arrival) at three ground stations or three orbiting satellites.

BTW TCAS II does not care about ADS-B out message. It uses reply delay and a directional antenna to determine traffic position. Proven to be very effective.

José
 
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Piloto said:
That is true. But an ADS-B out transponder is just a conventional Mode S transponder with Mode C capability also. The position reported on ADS-B out can be easily correlated with a Mode C interrogation by an ATC radar.
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Needing to use radar to validate the ADS-B messages is a gross waste and obviates the advantages of what ADS-B could be.
 
Art VanDelay said:
How do you know those items were "intentionally" turned off ? All we know for sure is that power was removed, by what method remains to be seen.
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I just go by what those involved in the investigation say on TV. When ACARS is turned off by hand it sends a message indicating that is going off the air and messages are completed before shut down. When power is suddenly removed there is no parity bit sent on the last message, the message is incomplete. Is the same when you turn off a computer by its switch vs pulling the power cord.

José
 
Bob Noel said:
Needing to use radar to validate the ADS-B messages is a gross waste and obviates the advantages of what ADS-B could be.
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May be not when you are dealing with thousands of lives arriving at JFK daily. Just like a young hacker on the internet can screw up things. The same kid can broadcast a bunch of ADS-B out messages of nearby planes from an ADS-B out transponder connected to a lap top. After all these transponders are RS-232 compatible making them a perfect match for the above scenario. But when the radar interrogates in mode C you can locate the hacker or at least determine the real planes.

If the ADS-B out hacker can not afford an ADS-B out transponder he can just put out a CW signal on 1090 MHZ and block all the ADS-B out messages. Similar as stuck mike on tower frequency. But with Mode C ground radar the most he will block is one scan segment (2 deg) and the controller would not be affected unless there are planes on the same segment

José
 
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Piloto said:
May be not when you are dealing with thousands of lives arriving at JFK daily. Just like a young hacker on the internet can screw up things. The same kid can broadcast a bunch of ADS-B out messages of nearby planes from an ADS-B out transponder connected to a lap top. After all these transponders are RS-232 compatible making them a perfect match for the above scenario. But when the radar interrogates in mode C you can locate the hacker or at least determine the real planes.


José
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basically you just agreed with my point that ADS-B is flawed.
 
Piloto said:
May be not when you are dealing with thousands of lives arriving at JFK daily. Just like a young hacker on the internet can screw up things. The same kid can broadcast a bunch of ADS-B out messages of nearby planes from an ADS-B out transponder connected to a lap top. After all these transponders are RS-232 compatible making them a perfect match for the above scenario. But when the radar interrogates in mode C you can locate the hacker or at least determine the real planes.



If the ADS-B out hacker can not afford an ADS-B out transponder he can just put out a CW signal on 1090 MHZ and block all the ADS-B out messages. Similar as stuck mike on tower frequency. But with Mode C ground radar the most he will block is one scan segment (2 deg) and the controller would not be affected unless there are planes on the same segment
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Encryption was widely available and understood when the standard was written. What you're describing is known as a "design screwup".
 
Piloto said:
I just go by what those involved in the investigation say on TV. When ACARS is turned off by hand it sends a message indicating that is going off the air and messages are completed before shut down. When power is suddenly removed there is no parity bit sent on the last message, the message is incomplete. Is the same when you turn off a computer by its switch vs pulling the power cord.

José
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If I had nickel for every time I've seen the message "ACARS DATA LINK LOST" I'd be a very wealthy man. On typical flight it kicks off all by itself at least once.
 
Art VanDelay said:
If I had nickel for every time I've seen the message "ACARS DATA LINK LOST" I'd be a very wealthy man. On typical flight it kicks off all by itself at least once.
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Perhaps when turning? Wings and the fuselage are pretty good at antenna blocking.
 
Bob Noel said:
basically you just agreed with my point that ADS-B is flawed.
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100% with you. Wonder if Air Force One is going to broadcast ADS-B out position to make it easier to track by Bin Laden relatives?

José
 
Art VanDelay said:
If I had nickel for every time I've seen the message "ACARS DATA LINK LOST" I'd be a very wealthy man. On typical flight it kicks off all by itself at least once.
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At nickel per event it would take 20million events just to accumulate $1m. You are better off with your salary:)

José
 
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