The NOAA-15 polar orbiting satellite sounder configuration consists of the 20-channel (19 infrared and 1 visible) HIRS-3 , the 15-channel AMSU-A , and the 5-channel AMSU-B atmospheric radiometers. The 5-channel AVHRR visible and infrared imager is used for cloud detection. These sensors provide a combined surface, atmospheric temperature, atmospheric moisture, and cloud measuring capability. Note that the molecule notations above the spectrum indicate where specific atmospheric gases are actively absorbing and re-emitting radiation as it travels through the atmosphere and into space.