Today 2024-12-23 at 11:49 UTC, I received an SSTV image from the RUZAEVKA-390 (RS44S) satellite.
I used a yagi antenna with linear polarization and kept the antenna fixed in one position. In the received image, I have 4 noise lines (I believe this is the moment when the satellite rotates and loses polarization). See the received image:
Basically yes, you will see rotation speed in the nulls.
Depending on the shape of the object it will also have complex rotational pattern, like Veritasium demonstraded.
You will also need to take the transmitter antenna lobes in consideration, how may nulls does it have and where.
This all combines with polarization nulls which is usually pretty strong when receiving with a linear antenna.
I use RHCP (x-yagi, helical) in most of my UHF stuff and these polarization nulls are usually much less visible.
Hi, I already did some spin-analysis on the PY4-satellites using the RSSI and SNR-values over several minutes. I put the values in an Excel-sheet and did a FFT with scilab. Finally I got 2 peaks in the FFT, showing the rotation speed across 2 axes, matching the spin-rate from the telemetry data.
Btw, its a common misunderstanding, that polarization-offsets would cause the most of the fading during rotation. This is only one component, that causes fading, the most important factors are the beam of the antenna, pointing somewhere into space, away from the groundstation and the obstruction of the antenna by the spacecraft (a good example for this is the ISS-FM-repeater, often unreachable, because the antenna is somewhere inside this big, well stabilized complex, unvisible from earth). Usually the blackouts by obstructions, are visible in the image as noisy lines, but in your image they are not equal spaced, so there is most likely a different cause.
