I think they should have just found a way to pop/puncture the ballooon. Clearly the missile[1] struck and destroyed the payload, which already makes the analysis difficult. Fragmented all over the place at the moment of destruction, all the bits then tumbling down tens of thousands of feet with continuing horizontal motion (inertial and whatever aerodynamic random-walk they'd move around with), then hitting water
hard, then (at least some bits) sinking.
Would have needed perhaps a hand-guided (or programmed visual-targetting system, like the autonomous impactor from the Double Asteroid Redirection Test) solution to puncture (ideally) or shred (most likely) the balloon canopy. Act as a streamer-chute, to a greater or lesser degree, as the (intact, at least at first, or at least
mostly intact at first) payload stays (~)intact at least until hitting the water, tracked all the way to make for an easy single-spot (plus subsequent drift, based on currents and what bits float easiest) recovery mission.
I suppose the falling payload
could be told to do a complete bitwipe (autonimously, or semi-autonomously via remote activation, as it was identified as now falling) that fragmented data-holding devices cannot be made to do. Any more than the various stages of physical destruction already do. But
if I was a Chinese operator, in contact with it, I'd probably have remotely prompted it to obfuscate/forget all ELINT-type data well before it got 'safely' over the Atlantic. Depending upon what its True™ mission actually was, as to what actual point that would be (between being first detected and its ultimate demise), against the continuing usefulness of the mission.
In actuality, unless it is shown to have had
significant horizontal[3] control/thrust, I can all too easily imagine it's just as the Chinese say and a passive (or at least non-military) atmospheric experiment gone adrift beyond where it was planned to investigate. Noting that a second one has been identified[4] going over the Caribbean/South America. Likely at least one of those is not where it was intended to go, unless they (and any others) are intended to form a 'chain' of coverage all the way across the entire Americas.
And who
hasn't wondered if they can some day just release some arbitrarily-loaded balloon and see how far it would end up going? Or how high... But if you were Ok with keeping it well away from uncontrolled bursting, at the extremes of balloon-capable altitudes, and could keep it reasonably powered for arbitrary lengths of time (e.g. whacking great solar panels, refilling the batteries for the better part of half of every daylight cycle that passes) then perhaps you could indeed end up with something very like what they shot down. Which doesn't negate the possibility of a military/intelligence purpose... going horribly wrong
or just-as-horribly right. And, unless the debris is an entirely unambiguous indicator that it's only a civil/sciency thing, we are only too easily left with (perhaps justifiably, like a 'stopped-clock') an amount of paranoia and accusative rhetoric in diplomatic circles.
[1] I heard "heat seaking" mentioned, but it would seem to me that a radar-locked one would have worked more assuredly (to get the result they did). Not knowing what sort of heat-profile the payload actually had, and no doubt prior investigations might have identified a nicely simmering object
not actually so much like the ambient air it was in. But, sure as Betsy, it'd have chunks of metal (assuming not built with full-on stealth-tech[2], which I doubt) that show up well in a guidance module's logic circuitry...
[2] In which case they could have gone with diluted-airflow radiators to reduce its IR signature, too.
[3] Vertical control (as
somewhat demonstrated before) can be used in combination with knowledge of various winds at various altitudes to expedite, linger and even steer a balloon's motion. And with remote control, rather than merely pre-'programmed' triggers of electromechanical responses to temporal and situational cues, you could possibly even tactically take advantage of developing information. But it's a poor replacement for blimp/semi-rigid/rigid aeronautics with significant ability to make a chosen headway (at least partially regardless of the wind) or somewhat maintain station-keeping as required.
[4] Whether only because of hightened awareness, I don't know. It could be that you can't
not spot them, and there are indeed these two that have 'gone off-piste'. Or failed to complete some pre-programed descent phase before going beyond their intended scope.