There's a reason why I took my inverter offline after making sure that it was installed correctly. A cheap power meter now serves to measure my power generation instead.
Taking it offline doesn't protect against supply chain attacks in the form of built-in kill switches. A satellite could transmit signed instructions by modulating light below the noise floor, inverters must sense the voltage/current state of the PV panels anyway for MPPT to work.
Only deep inspection of the silicon and code can improve the situation.
Perhaps Western blocks could develop provably secure silicon IP and code, formally verified, and perform continuous random sampling on imported goods, including full multilayer silicon inspection; publish it for free and refuse to import products that don't cooperate.
I'm curious about the feasibility of modulating light onto a solar panel. I feel it would not be feasible, except possibly onto a single panel at a time over a long time period. Just a gut feeling based off radio stuff (GPS).
GPS can provide the coherent reference, if you mean transmitting signal (say sound) while the panel is illuminated by the sun theres youtube videos of people doing that, with a laser pointer, but in sunlight and without information theoretic justified modulation scheme.
Nothing prevents the satellite to transmit the commands at night, if that feels more convincing to you.
Ask yourself what is the active area of a photodiode in your TV/... ? What is the active area of your light-bucket on a roof?
I'm not at all claiming this is happening, I'm claiming this is very feasible to do. Consider the aperture (area) of a camera or telescope, how many times can you fit this area into a domestic solar panel installation?
If we are discussing the solar panel that powers your outdoor garden light, I don't suggest to apply the precautionary principle, but we are talking about products that sum up to a significant fraction of grid power generation.
