BFO Graph midpoint line
Gysbreght,
The midpoint line would be heavily influenced by the satellite movement, and the relative direction of the plane from the satellite. The satellite movement is sinusoidal, and the impact of the plane's location is far from linear (also containing a at least two trig function dependencies).
The orange mid-track line should be drawn on top of the other lines up to the point where the two paths diverge (~18:28). As drawn, the section of the orange line 18:28-29:41 is too low. (although, correcting that gives the orange line two distinct turns...)
It is the satellite reversing direction around 19:41UT (as just one of the contributors to the BFO) that puts the turn in each of the possible tracks.
- If the plane is to the North of the satellite, the satellite changes from approaching to moving away.
- If the plane is South of the satellite, then the satellite changed from receding to approaching.
Combining in the other BFO contributions leads to the appearance that the North track turns at a different time (20:41) than the South track (19:41). But, the lines drawn between data points are NOT real... We only have discrete measurements, with no indication on the chart of the BFO values in between. If you model the intervening times and fill in the expected BFO values, the two lines show a better symmetry, with the line turning closer to the actual satellite reaching its Northernmost point. (quite close to 19:41UT).