Moving mirrors make the radiometer view different regions of the earth. The instrument begins by looking off in one direction and then scans across a scene making observations as it proceeds. Data is recorded in a two-dimensional format which, when displayed on a computer monitor or television screen, makes up an image. The radiation coming from each pixel is presented in an image format in terms of a grayscale. An image consists of 256 gray shades, ranging from 0 for pure black to 255 for pure white.
All objects emit electromagnetic radiation.
The infrared radiometers on satellites measure radiation with wavelengths of 10 to 12 m m. For easy interpretation, the radiant energy measured by infrared radiometers is converted to a temperature. Cold objects are white and hot surfaces appear black. Time sequences of infrared images are animated and shown on television news programs. The following interactive exercise is an introduction to interpreting satellite weather images typically seen on evening news.