BOS instrument. The black and white coated detectors weights are 0.8 and 160 g, respectively. The black surface integrates all electromagnetic radiation, whereas the white channel is only sensitive to the infrared radiation. m₁ is fully isolated from m₂ by a multilayer material. The black centre is connected to the top of the rod, which dissipates in the white ring m₂. The two thermistors T₁ and T₂ measure the temperature at each extremity of the rod.