You can't work with an average, squashing together the way heat radiation goes through the dense, warm, humid lower atmosphere with the way it goes through the thin, cold, dry upper atmosphere.

The EKV's cooled infrared sensors will be capable of detecting even the smallest amounts of heat radiation.

Spitzer's IR instruments can capture the heat radiation put off by dust particles in the ring, which starts some 3.7 million miles from Saturn and extends outward another 7.4 million miles.