Originally Posted by
hamster3null
It's a good observation. But I have two points to make:
* If you do a least mean square fit for all points except around 120 min, I think you'll find a scaling factor that is somewhere above 0.25 (not 0.15-0.2), and, at that scaling factor, you can't get the "possible turn" peak to match the data at _any_ heading.
With a scaling factor of 0.25 (instead of 0.15-0.2), the 1st plot of the 2nd page of my doc would basically be translated higher (the 120 min peak would reach approx 290 Hz instead of 250 Hz): it would still be possible to reproduce the 120 min turn but no longer the initial conditions (already out of the enveloppe) and even around 180 min (the min enveloppe would be at 125 Hz slightly higher than the BFO).
Originally Posted by
hamster3null
* But if you assume that MH370 was climbing at around 18:25 UTC when the "peak" was observed, you can fit the peak nicely to the course before the turn. Put in something like ground speed 480 kts, heading 285, climb rate 4000 fpm. Recall that the Malaysian military radar picture has a "hole" in the track. It could be consistent with dropping to 5000' above the Strait of Malacca (for whatever reason) and then climbing back out.
Ok, this can kill this potential signature... 4000 fpm is ~22 m/s or ~14 m/s projected onto the LOS (@~40° of elevation)... which translates as a doppler of ~77 Hz (at 1640 MHz) hence 11.5 to 15.5 Hz after the scaling of 0.15 to 0.2... The last plot of my doc for the north trajectories shows that we need more than 50 Hz to get the BFO into the enveloppe of the tens of thousands of simulated flights. I would then need ~13000 fpm to fix the gap. But as RetirdF4 suggests, the ground speed would decline accordingly (also modifying the doppler), so I will introduce large altitude changes in the conditions you suggest to check it.
Originally Posted by
hamster3null
BTW, how do you get the 17:07 data point to fit? It's been one of the problems bugging me for a long time. I can force-fit it by setting the heading to 5, but it's pretty artificial because we have the FR24 track up to 17:20 and it is showing straight and level flight at heading 25 from 17:01 to 17:20.
I got these runs fitting the 17:07 value of the BFO through the MonteCarlo simulation: among the thousands of simulated runs, some of them happens to replicate this inflexion at 17:07... this is exactly the same for the ~18:30 turn (some of the thousands of simulated runs replicate the peak), it seems to rely on a precise relative timing between the bearing changes (we need a turn around 17:07 to generate it) and the handshake instants.
Jeff
PS) a scaling factor between 0.15 and 0.2 is close to the wavelength value at 1640 MHz (0.1825 m): would it be possible that the Inmarsat BFO plot is plotted with a wrong unit (m/s instead of Hz) ?
PPS) to RetiredF4: note that these models/assumptions for the simulated trajectories does not hold at the 120 min turn, the only assumption behind the potential signature is the turn (toward the south or the north) itself... these assuptions apply more to the following hours of flight .