To capture the balloons at high altitude may not be so hard if we use a similar balloon that can travel a little faster. We could use a deploy-able rotating hooked whip at the bottom of the balloon with a high intensity flash that would allow us see the rotations in concert with an onboard stationary camera. Once hooked it could be towed, maybe if it strong enough we could also have an onboard small javelin/spear/gun to pop i, if necessary. If the balloon had some type of hook on the top or around it, framing it, we might be able to grab it also mid flight by some other aerial vehicle too.