Originally Posted by
MechEngr
The envelope itself will be practically transparent in IR. The seeker found the instrument platform and destroyed that.
The reason for trajectory planning for a gun? Because not every problem benefits from an air-to-air missile. To recover the instrument package with the least damage a few shots (they can make multiple passes) would ventilate the balloon to a suitable descent rate.
The descent rate could become unsuitable as the envelope entered the lower atmosphere, Boyle being Boyle and the mass of gas being decreased.