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Satellite company lying about MH 370's crash site

solletica

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According to Immarsat, the comapny was able to pinpoint the plane's last location from the Doppler shift in the wavelength of the pings generated from the plane. . .

A key calculation done by Inmarsat was determining the “Doppler shift” in the ping, or the slight change in the frequency of the signal caused by the movement of the aircraft relative to the satellite in space.
“From that process – a compression or an expansion of the wavelengths – you can determine whether the aircraft is getting closer or farther away,” McLaughlin explains. “It’s been a groundbreaking but traditional mathematics-based process that was then peer-reviewed by others in the space industry, and indeed contributed to by Boeing.”
The data analyzed was generated by pings from MH370 to one of Inmarsat’s 10 satellites. McLaughlin likened the Inmarsat avionics and antenna on an aircraft to a mobile phone, while the applications that use the satcom link, including the Aircraft Communications and Reporting System (ACARS), are “apps.” On MH370, “the apps were turned off, but the handset wasn’t,” he explains.


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Except this makes no sense from physics. The Doppler shift of the wavelength of radio waves is way too small to be detected when the source (i. e. airplane) is moving at speeds much less than c. Doppler shifts are only easily measured for subluminal waves, i. e. sonar.

The satellite would've had to be specifically designed to pick up such small shifts--a very expensive endeavor, and so there would've been no reason to make it do that. Each satellite was designed to transmit data to planes, not determine its altitude, location, etc.

More than one satellite would've had to have picked up the pings for Immarsat to use that data to determine the plane's exact location at the time of the last ping.
 

ttwtt78640

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The claim was not that the signal system could pinpoint the aircraft's location precisely, it was that it could distinguish between a northwestern path and a southwestern path that differed by many thousands of miles.
 

solletica

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The claim was not that the signal system could pinpoint the aircraft's location precisely, it was that it could distinguish between a northwestern path and a southwestern path that differed by many thousands of miles.

It wouldn't have been able to do that using Doppler data, because the satellite couldn't have detected such a small Doppler shift.
 

DaveFagan

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It wouldn't have been able to do that using Doppler data, because the satellite couldn't have detected such a small Doppler shift.

I was under the impression that the sound of a train moving away could be discerned by human hearing because of the Doppler Effect. It seems if humans can perveive that, then math and electronics should be able to do it easily.
 

longview

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It wouldn't have been able to do that using Doppler data, because the satellite couldn't have detected such a small Doppler shift.
I am thinking somebody dropped in a term they did not understand (doppler)
We cannot tell much from the Immarsat page but they say they can provide data to 50 Mbps.
Our satellites - Inmarsat
This means they likely have a carrier running at least at 12 mhz.
If they had access to the analog section of the data, they could measure the difference between
ping round trip times to within one wavelength of the carrier, 1/12 mhz= .08us.
C= 186 282.397 miles per second, so a mile is about 5.4 us
A jet liner at cruse could cover about 600 miles in an hour, or a difference of about 3 ms.
I think seeing a ping time difference of 6ms (round trip) is well within the capability
of a modern telecom satellite.
 

Redress

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It wouldn't have been able to do that using Doppler data, because the satellite couldn't have detected such a small Doppler shift.

Ummmm...police radar guns work in large part by measuring the Doppler shift.
 

solletica

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I was under the impression that the sound of a train moving away could be discerned by human hearing because of the Doppler Effect. It seems if humans can perveive that, then math and electronics should be able to do it easily.

Read my OP. Sound wave Doppler shifts can be easily measured and heard, but radio wave Doppler shifts can't.
 

Redress

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Read my OP. Sound wave Doppler shifts can be easily measured and heard, but radio wave Doppler shifts can't.

Yes they can. Depends on the frequency to an extent, but that is how, for example radar guns measure speed, measuring the Doppler effect on radio waves.
 

RabidAlpaca

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Read my OP. Sound wave Doppler shifts can be easily measured and heard, but radio wave Doppler shifts can't.

*sigh* People have pointed out that you don't know what you're talking about concerning the doppler effect and technology, and it might be time you start believing them. Police radar guns use microwaves, not sound waves, and it can be measured extremely accurately. This technology has existed for decades.

Police RADAR
 

solletica

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*sigh* People have pointed out that you don't know what you're talking about concerning the doppler effect and technology, and it might be time you start believing them.

Police RADAR

The police radar DOES NOT detect the Dopper shift directly. If you saw in the article, it measures the beat frequency which is measured after the destructive interference of the transmitted and reflected waves.

There's no beat frequency when the airplane pings the satellite because there's no reflection involved. The satellite is not a radar device.

You really should read what you cite and/or do some basic research before claiming that others "don't know what they're talking about."
 

solletica

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Yes they can. Depends on the frequency to an extent, but that is how, for example radar guns measure speed, measuring the Doppler effect on radio waves.

They cannot, unless as pointed out, the transmitter is merely picking up a reflected Doppler-shifted wave, in which case the beat frequency (from interference of the transmitted/received waves) is measured.

Although it is possible to measure an electromagnetic Doppler shift w/out a beat frequency, it requires extra electronics and/or more sophisticated DSPs and such a feature would not exist in a device unless it were needed.
 

solletica

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I am thinking somebody dropped in a term they did not understand (doppler)
We cannot tell much from the Immarsat page but they say they can provide data to 50 Mbps.
Our satellites - Inmarsat
This means they likely have a carrier running at least at 12 mhz.
If they had access to the analog section of the data, they could measure the difference between
ping round trip times to within one wavelength of the carrier, 1/12 mhz= .08us.
C= 186 282.397 miles per second, so a mile is about 5.4 us
A jet liner at cruse could cover about 600 miles in an hour, or a difference of about 3 ms.
I think seeing a ping time difference of 6ms (round trip) is well within the capability
of a modern telecom satellite.


But the satellite would've had to have been specifically designed to detect frequency changes, as pointed out in the OP. The Immarsat satellite was apparently not used for that purpose; it was used simply to transmit data to subscribing airlines after receiving a ping.


Second, the plane was not flying directly toward or away from the satellite, it was flying parallel to the Earth's surface, so only the x (horizontal) component of the velocity would've been reflected in the Doppler shift--a very small amount.


And even assuming that the such minute Doppler shift detection were implemented in the satellite, the satellite company would have to know the exact speed and altitude of the plane at the time it sent its ping to be able to use the Doppler shift information to determine its exact location at the time of the ping--because several combinations of speed and altitude would have resulted in the same Doppler shift. Speed and altitude were not known at the time of the ping because the plane's ACARS and transponder was switched off.


And then even then, it would have to make an assumption about how fast it traveled after that to know its final destination.
 

longview

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But the satellite would've had to have been specifically designed to detect frequency changes, as pointed out in the OP. The Immarsat satellite was apparently not used for that purpose; it was used simply to transmit data to subscribing airlines after receiving a ping.


Second, the plane was not flying directly toward or away from the satellite, it was flying parallel to the Earth's surface, so only the x (horizontal) component of the velocity would've been reflected in the Doppler shift--a very small amount.


And even assuming that the such minute Doppler shift detection were implemented in the satellite, the satellite company would have to know the exact speed and altitude of the plane at the time it sent its ping to be able to use the Doppler shift information to determine its exact location at the time of the ping--because several combinations of speed and altitude would have resulted in the same Doppler shift. Speed and altitude were not known at the time of the ping because the plane's ACARS and transponder was switched off.


And then even then, it would have to make an assumption about how fast it traveled after that to know its final destination.
I do not think they were doing doppler, but rather just ping distance.
The CNN graphic gave a good example,
How 'groundbreaking' number crunching found path of Flight 370 - CNN.com
one ping is a circle, two pings a straight line, three a start of a curve.
They do not know if the plane was north or south of the satellite, from the pings,
but think they can eliminate the north route.
According to CNN they then validated their math with known plane routes.
 

solletica

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Yes, the satellite company has no clue what it's talking about. It didn't know the altitude of the plane at the time of the ping, and without that, one can't compute the speed of the plane at the time of the ping.

If the altitude were known, the speed could be computed, but the exact position couldn't be known.

The satellite company says their analysis was based on detecting the speed or position of other planes, but in those cases, one of those quantities (speed, altitude, position) were known.

I actually did the math, and wasn't able to reproduce anything the satellite company claims. You would have to know altitude to compute the speed from the Doppler shift data.
 

solletica

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I do not think they were doing doppler, but rather just ping distance.
The CNN graphic gave a good example,
How 'groundbreaking' number crunching found path of Flight 370 - CNN.com
one ping is a circle, two pings a straight line, three a start of a curve.
They do not know if the plane was north or south of the satellite, from the pings,
but think they can eliminate the north route.
According to CNN they then validated their math with known plane routes.

It would be nice if they can show the public their math.
 

Helix

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Yes, the satellite company has no clue what it's talking about. It didn't know the altitude of the plane at the time of the ping, and without that, one can't compute the speed of the plane at the time of the ping.

If the altitude were known, the speed could be computed, but the exact position couldn't be known.

The satellite company says their analysis was based on detecting the speed or position of other planes, but in those cases, one of those quantities (speed, altitude, position) were known.

I actually did the math, and wasn't able to reproduce anything the satellite company claims. You would have to know altitude to compute the speed from the Doppler shift data.

the video at the link i posted explained it fairly well. there's also this :

How satellite

i truly doubt that there's a satellite company conspiracy to lie about the pings.
 

longview

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Yes, the satellite company has no clue what it's talking about. It didn't know the altitude of the plane at the time of the ping, and without that, one can't compute the speed of the plane at the time of the ping.

If the altitude were known, the speed could be computed, but the exact position couldn't be known.

The satellite company says their analysis was based on detecting the speed or position of other planes, but in those cases, one of those quantities (speed, altitude, position) were known.

I actually did the math, and wasn't able to reproduce anything the satellite company claims. You would have to know altitude to compute the speed from the Doppler shift data.
The tools they are using are very crude, because as you point out,
they were not designed to make that type of measurement.
The ping just gives a delta time from a geosynchronous satellite over a fixed location.
The error for the altitude would be about 8 miles (40,000 feet), add to that maybe 2 more miles,
for the counter resolution.
Six pings, six data points on a 10 mile wide line, draw the line north and south.
Compare this with known tracked planes, to validate the math.
It is still a guess, but an educated one.
 

longview

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It would be nice if they can show the public their math.
I don't think their math is complicated.
The Satellite in orbit is at 22,236 miles over the equator.
I think they said they have 6 pings which all represent different distances from the satellite.
If the earth were flat, these data points would make a straight line, the Earth is a sphere,
so the line becomes a curve.
They do not know weather it is north or south of the equator, but the northern track
would have taken the Jet into controlled airspace I.E. someone's radar.
The error could be 10 miles wide, and the distance from the last ping could be up to 600 miles.
 

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There's already a gigantic thread in the CT section about this flight, and it's demise. Should this thread be combined with that one?

Sounds about the same.
 

solletica

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the video at the link i posted explained it fairly well. there's also this :

How satellite

i truly doubt that there's a satellite company conspiracy to lie about the pings.

You need to actually do the math (w/the equations and everything) to see that it's lying. The Doppler shift data is based on the angle between the line between the plane's transmitter and the satellite and the direction and velocity of the plane parallel to the ocean.

Put another way, the relevant velocity difference used to compute the Doppler shift is simply

v = ds/dt

where s is the distance between the satellite and the plane's transmitter (on top, presumably), and t is time. As the angle between the line connecting the transmitter to the satellite and the plane's direction of flight increases, ds/dt increases.

So the wider that angle, the more the plane's velocity contributes to the Doppler shift.

However, that angle also depends on the plane's altitude, which was not known at the time of the ping. If the satellite company were claiming that it incorporated the altitude into its calculations, then its conclusion would be plausible, but it didn't. See your own cite.
 
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solletica

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There's already a gigantic thread in the CT section about this flight, and it's demise. Should this thread be combined with that one?

Sounds about the same.

I posted it here because this solely deals w/the technical details of the mechanism Immarsat used to determine the plane's speed (to narrow its position).
 

Helix

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You need to actually do the math (w/the equations and everything) to see that it's lying. The Doppler shift data is based on the angle between the line between the plane's transmitter and the satellite and the direction and velocity of the plane parallel to the ocean.

Put another way, the relevant velocity difference used to compute the Doppler shift is simply

v = ds/dt

where s is the distance between the satellite and the plane's transmitter (on top, presumably), and t is time. As the angle between the line connecting the transmitter to the satellite and the plane's direction of flight increases, ds/dt increases.

So the wider that angle, the more the plane's velocity contributes to the Doppler shift.

However, that angle also depends on the plane's altitude, which was not known at the time of the ping. If the satellite company were claiming that it incorporated the altitude into its calculations, then its conclusion would be plausible, but it didn't. See your own cite.

it said in the Chinese article that they determined that the plane maintained cruising altitude, so they must have used the signals coming from other planes nearby at known heights to figure it out. you don't have access to the data that they have, so that's why your own formula probably isn't working. you just don't have all of the regional flight data from that time period.

seriously. your allegation that the satellite company is engaging in a purposeful hoax it just really unlikely.
 

solletica

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it said in the Chinese article that they determined that the plane maintained cruising altitude,

How could anyone know that the plane maintained cruising altitude if the plane didn't report any altitude information and there was no primary radar to detect it? Explain that.

so they must have used the signals coming from other planes nearby at known heights to figure it out.

How do other planes know the altitude of MH 370? The transponder and ACARS aboard the plane was off. Doesn't make sense.

you don't have access to the data that they have, so that's why your own formula probably isn't working. you just don't have all of the regional flight data from that time period.

True, my calculation was based on all publicly available data. If the satellite co. has additional data, it should share it. Otherwise, based on what's been reported, its conclusions are inconsistent w/the math.

Actually, the satellite co.'s conclusion that the plane crashed in the ocean based on its analysis of Doppler shift data is unlikely, because

1) A hijacker/commandeering pilot wouldn't go through all this trouble just to commit suicide. If the pilot wanted to ditch the plane in the ocean, he would've simply done at it the earliest opportunity, not flown a complex flight plan.

2) Immarsat would have no reason to incorporate Doppler shift analysis ability in their satellites, because they're not used to track altitude/speed, only to relay information to subscribing airlines.
 
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Helix

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How could anyone know that the plane maintained cruising altitude if the plane didn't report any altitude information and there was no primary radar to detect it? Explain that.



How do other planes know the altitude of MH 370? The transponder and ACARS aboard the plane was off. Doesn't make sense.



True, my calculation was based on all publicly available data. If the satellite co. has additional data, it should share it. Otherwise, based on what's been reported, its conclusions are inconsistent w/the math.

Actually, the satellite co.'s conclusion that the plane crashed in the ocean based on its analysis of Doppler shift data is unlikely, because

1) A hijacker/commandeering pilot wouldn't go through all this trouble just to commit suicide. If the pilot wanted to ditch the plane in the ocean, he would've simply done at it the earliest opportunity, not flown a complex flight plan.

2) Immarsat would have no reason to incorporate Doppler shift analysis ability in their satellites, because they're not used to track altitude/speed, only to relay information to subscribing airlines.

the satellite would be tracking the other planes, too. that's probably how they figured it out.

i see two likely scenarios :

1. the plane was hijacked, something went wrong, it depressurized, and then flew until it ran out of fuel.

2. the plane wasn't hijacked, something went wrong, it depressurized, and then flew until it ran out of fuel.

as for sharing all data, i'm totally with you on that one. the Malaysian government has done a pretty poor job of that.
 
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