40,000 foot range, has it happened before? and second of all, why did you -- can you say more about why you knew that last balloon or object was from china whereas this one you don't know? >> so in terms of this particular object, again, as i highlighted, we don't know where it's from. it posed a reasonable threat to civilian air traffic, and so the determination was made to take it down. in terms of the other balloon, as i mentioned in our previous briefing, we have learned a lot about the chinese surveillance high altitude balloon program. we've gathered a lot of information over the last couple of years, and so we were able to based on that information detect it at a very early stage as it approached u.s. airspace, we had a good understanding of what it was. as i mentioned we were able to monitor closely, track it over the continental united states, learn a lot about it, and take