Yes, I was thinking of having the sensors all over a few parsecs. A lot like hunting for wrecks nowadays. They don't expect to find a lot or often and it does take some luck and a lot of investment before hand. Bruce, I am not sure if you were pro or anti idea with your Webb statement.
Does this not qualify as direct observation of a planet's atmosphere, Leonard?
Degree of ark of observation might be solved by many techniques that are coming online now. At TL 15? I could not say but I would be willing to think it could be done and at a profitable price.
What if tech like this were used to cover a 100m sphere. Seems to me you could have a good 360 by 360 coverage of the whole sky at TL 15.
A last point, does not jump flash have a signature that is artificial enough to pick out from the background noise? I would think the radiation signature would be very odd.