lulu-the-dog
Have been following the thread with interest from the initial sad loss.
Would I be correct to say that the Inmarsat satellite technology that has lead the search to the Indian Ocean has not previously been used to locate a lost aircraft? Perhaps we would have been more surprised to find it?
It seems to me that while the mathematics etc are very plausible, at the end of the day the technology is unproven to say the least. Maybe its time to start over?
docrohan
While the application is new, the basics are very old....1842 to be exact
The doppler effect analysis is all they have to go on ATM....as far as we know
Although the ages old Doppler shift calculations have been newly applied to the geostationary Inmarsatt satellite the use of this technique is not new in modern day satellite Search And Rescue operations.
The COSAPAS/SARSAT polar orbiting (non-geostationary) satellites perform mathematical calculations based on the Doppler-induced frequency shift received by LEOSAR and MEOSAR satellites as they pass over a beacon transmitting at a fixed frequency. From the mathematical calculations, it is possible to determine both bearing and range with respect to the satellite. The range and bearing are measured from the rate of change of the received frequency, which varies both according to the path of the satellite in space and the rotation of the earth. This allows a computer algorithm to triangulate the position of the beacon with 2 or more passes. A faster change in the received frequency indicates that the beacon is closer to the satellite's ground track. When the beacon is moving toward or away from the satellite track due to the earth's rotation, that Doppler shift also can be used in the calculation.
Bear in mind that the difference here is that the COSPAS/SARSAT LEOSAR satellites are moving whilst the Inmarsat satellites are stationary relative to the Earth. But the principle remains the same and is well established. The calculations would be similar whether the target or the receiver is moving.
Inmarsat has said they have peer reviewed their data with other industry specialists; they may have consulted COSPAS/SARSAT Doppler shift experts.
Here are some background links:
Cospas-Sarsat System - International COSPAS-SARSAT
International Cospas-Sarsat Programme - Wikipedia, the free encyclopedia
My conclusion is that the location of a target by a satellite using Doppler shift has been proven many times before and although it is a new technique for Inmarsat birds, I think the maths can be trusted.