For a 10mt explosion at 20km height it shows a third degree burn radius of 27km. Chelyabinsk was ~0.5kt at 29km. Larger objects are expected to penetrate further into the atmosphere before exploding: https://en.wikipedia.org/wiki/Meteor_air_burst
I'm not sure how much time you'd have to evaluate size or distance, videos of Chelyabinsk show it pretty bright just a second or two after becoming visible. Length of infrared exposure determines severity of burn, so reacting early is helpful.
For a 10mt explosion at 20km height it shows a third degree burn radius of 27km. Chelyabinsk was ~0.5kt at 29km. Larger objects are expected to penetrate further into the atmosphere before exploding: https://en.wikipedia.org/wiki/Meteor_air_burst
I'm not sure how much time you'd have to evaluate size or distance, videos of Chelyabinsk show it pretty bright just a second or two after becoming visible. Length of infrared exposure determines severity of burn, so reacting early is helpful.