Strange Object in Nuclear Bomb Video - UFO??

I was watching a video compilation of nucear bombs exploding (as you do lol) and saw a strange object floating in the top of the screen. The object appears at around 1 minute 50 seconds in the top left of the screen maybe you guys could take a look and solve the mystery. It looks like a bubble or something but maybe it can be solved very easily! Take a look.

you tube video

My guess is that they may have released some balloons to give an indication of airflow. Just a guess but it looked like a plain 'ol balloon to me....

Probably a balloon with instrumentation (sp) being sent up to take atmospheric readings. (Slightly off topic but why has no one ever used Manhattan Project by Rush for one of those videos????).

Cheers guys it did look like a balloon just seemed a bit weird to release one like that. Are the instruments attached to it how big are these balloons usually?

I'd say a balloon too. Lets not rule out that it was a marker or just some regular balloon shaken loose by the blast.