Maps of AO40's U-RX AGC

The following graphs are maps of (averaged) AGC readings of AO40's 435 MHz receiver (U band), with data from orbits 1134 through 1161.

Both plots are actually maps of the entire earth, with the North Pole at the top, South Pole at the bottom, and the 0 degree meridian (Greenwich) in the center.

These plots should be interpreted with a LOT of caution; see some remarks at the bottom of this page.

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The first map is a plot of the average AGC value versus the location of the sub satellite point.
The top coloured line is the scale: from blue = -1.7 dB at the left to yellow = 25.8 dB at the right.

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The second map shows for every location on the earth's surface the AGC value averaged over the time the satellite was above the horizon at this location.
The top coloured line is the scale: from blue = -1.3 dB at the left to yellow = 4.4 dB at the right.

Note: in both graphs, the averaging is done on a linear scale, not on the dB scale.

Particularly the second graph should be interpreted with lots of caution, because we only have measurements available at a rather restricted series of points in space.

For example, the yellow parts of the second graph suggest that the station disturbing AO40's 70 cm receiver may well be located somewhere in the north Atlantic, near the North Pole.
However, this is probably due to the AGC just happening to be hit once very hard when AO40 was at apogee, precisely at the only time AO40 was visible at those northern locations. The station causing the AGC to rise may however have been anywhere in the footprint, but less active at other times.

In fact, I doubt that anything significant can be concluded from these graphs, but since I made them, I thought I'd make them available anyway.

For comparison, here is a similar graph, made using data from November 2002 through February 2003 (orbits 921 through 1070). This is a period in which AO40's attitude was near ALON/ALAT=0/0, and the transponder was normally on.

One might hope to see concentrations of signals in areas like Europe and the US, but that clearly is not the case.
That's one more sign that these plots are very hard to interpret. Or that some more smart processing of the data is needed in order to get a useful plot...

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Scale: from blue = 5.6 to yellow = 18.0 dB.

Comments, and suggestions for improvements of the maps are welcome, of course.