The problem was that the instrument was subject to the same heating as the x-ray laser rods, and there was no way to know if the signal they sent was from the laser heating the instrument, or the bomb.
The instrument was subject to the same heating as the x-ray laser rods. The problem was this. There was no way to know if the signal was from the laser. This laser was heating the instrument. This laser was heating the bomb. They sent the signal.