As an aerial photographic lab tech, I first assumed this was an aerial photo job. But the hours are all wrong. We never take photos late in the evening–the shadows obscure everything useful.
It could be Infrared photography, but you could do that at any time of the day.
Because it’s at noon, the late evening, and after midnight, it could be checking for unexpected changes in spots hidden from view on the ground. This method seems so inefficient though. The intervals seem too long. Of course this is conjecture. We should wait for the minds informed on this matter to speak up in this thread.
Spooking potential targets. By overtly being a public PITA they could be keeping potential terrorists off-guard. Kinda like that bloody fly making noise in a quiet room.
Tracking. While the FBI claims they are not doing electronic surveillance, who is to say they are not using other surveillance measures? They could be taking infrared photographs at different times of the day to establish a baseline. Once completed, it’s easier to spot the odd man out because he doesn’t fit in. Old WWII trick.
Diversion. With everyone looking up in the sky, is anyone watching what the FBI may be doing on the ground at the same time?
Why do you assume they are JUST looking at the ground?
Due to the heavy flight training in the area, Bloomington’s skies are awash with little airplanes. A C182 loitering around is more efficient at keeping a watch on them than a screaming fast F-16.
I also don’t believe for a minute that that is the ONLY airplane the FBI has up and about - it’s just the one assigned to those time slots.
There’s a lot you can see from a small plane you can’t see on the ground.
Actually, I work at a 24hr donut shop. We have a fax machine. People aren’t allowed to use it but faxes are recieved there for people (like my step-mom who picks up her newspaper routes).