I know “The Balloon” is pretty much out of the news cycle at this point, but I couldn’t help revisiting my original analysis once some more unclassified imagery came out.
In this photo, a madman U-2 pilot took a selfie while pursuing the balloon across US airspace. I noticed that the entire shadow of the aircaft was visible on the balloon’s surface. This gave me a second reference length (19.2 m) in addition to the 30.0 reference length in my original analysis.
These two reference lengths gave scale values of 1:366 and 1:355, respectively – a difference of less than 3%. To size the solar panels, I used their average: 1:360.5.
As you can see, the new estimate is 145% of the previous one, leading to a new power-generation estimate of 23 kW, assuming full solar irradiance.
Note that this is still an extremely coarse estimate. (For one, the U-2 shadow is being cast on a curved surface, so there’s some distortion there. Secondly, the aspect angle of the payload bus may be causing some solar panels to appear larger or smaller.) Still, since this is within the same order of magnitude as my original estimate, even with another reference length added in, I’m confident that this is a pretty close result as far as amateur analysis goes.