Calibrating out mechanical backlash and mis-alignment in the mountings I assume.
Should be crazy efficient compared to the terrible alternative which would require something like deliberately de-focusing all other mirrors only to be able to verify that the mirror under test actually does project the sun where expected.
Tempted to keep my initial upvote on the "investor hype" sibling, out of spite for all projects that do, but the ability to check arbitrary points in the nonilluminated volume for accidental illumination must really make do much of a difference I can't. Thanks for pointing me in the right direction!
Or just put up a big black board with reference points on it, and point a camera at that?
The beauty of the misalignment patrol drone is that it does not leave you guessing wich one exactly of your large number of inexpensive mirrors is out of line. The culprit clearly lights up in the video feed.
You can then use the camera image of the position of the sun spot on the black board to figure out your new calibration settings for this particular mirror.