having been partially involved in some high-altitude un-manned ballooning from the UK I have a few thoughts.
From the pictures that I have seen of the balloon and its payload there does not appear to be a parachute - there might be one packed inside somewhere, but we don't know that. If the balloon is shot and ripped/torn then the payload will come down rapidly; technically, it will 'plummet', then 'terminal velocity', and finally 'unscheduled disassembly on the ground'. At which point the Intell community will have lost much of there chance to examine it for information. They will be able to gather some info the smashed remains, but not nearly as much as they could from the intact payload (assuming it isn't booby-trapped!).
There are a couple of scenarios to consider -
- let it continue floating slowly across the entire USA, and when it gets close to the eastern shore of southern shore, then you attempt to bring it down, such that it lands in the sea. It would still be a destructive landing, but it won't cause any harm to land, property or people.
- attempt to introduce a very small hole in the envelope of the balloon, such that the lifting-gas is lost gradually, and the balloon descends gradually. It is still uncontrolled in which direction it is going, and it is going to cause quite some chaos in the US airspace, but it will come down eventually ... hopefully not in/on a major population centre, but cannot be guaranteed. The problem with this is that to introduce a tiny hole in the envelope is extremely difficult ... a pin-prick becomes a small hole, which becomes a small tear and then a large tear, which leads to the 'sudden plummet' outcome.
What the Intell people want is for it to descend gradually and gently alight in a field in the middle of nowhere ... the payload suspended underneath is not too damaged, and then allows extensive analysis of whatever is on board. If it does land in a built-up area then recovery might be a bit more of a problem, but still 'doable'. It also might land in the top of trees in a forest, which is not ideal.
If we were to assume that it was taking pictures of whatever it flies over, it is a trivial task to to convert those pics to a digital format and transmit them to a ground station (hell, amateurs and enthusiasts have been doing it for years ...) and it is theoretically possible for those same images to be transmitted upwards to a passing satellite for storage and later download when over China. But that's what the intell people will be able to tell if they get theirs hands on a complete payload.
It is possible that the balloon knows exactly where it is because of GPS. Could they switch-off GPS for a short while to see if it confuses the entire thing? Could they GPS-spoof to make the balloon think that it was back over Chinese territory and see it it has a "I'm home, I will descend to land" system?