Aerosol Instrument Trading Card

The SAGE instruments (I, II, and III) use a measurement technique called solar occultation or limb scanning to determine the amount of aerosols, ozone and other gases in the atmosphere. For the SAGE instruments, limb scanning refers to the manner in which the field-of-view of the instruments is scanned from the top of the Earth's atmosphere, or limb, to the Earth's surface while the instrument is viewing the sun. An important part of the SAGE instruments is a sun photometer which when used in the limb scanning mode measures the amount of sunlight transmitted through the atmosphere at different altitudes above the Earth's surface. This information can be used to determine the vertical distribution of aerosols and ozone in the upper troposphere and through the stratosphere.

The SAGE III instrument was designed so that it can also use sun light scattered from the moon (e.g. moon light) in addition to directly from the sun which greatly expands the global coverage. In addition to ozone and aerosols, the SAGE III instrument also provides global, long-term measurements of other key components of the Earth's atmosphere.