Used to assign a number to a characteristic of an object or event, which can be compared with other objects or events.  

Moderate Resolution Imaging Spectroradiometer (MODIS)

A key instrument aboard NASA’s Terra and Aqua satellites. MODIS instruments view the entire Earth’s surface every 1-2 days, acquiring data in 36 spectral bands. It plays a vital role in the development of validated, global, interactive Earth system models which aim to accurately predict global change.  

For more information, see NASA: MODIS.  

Multispectral Scanner System (MSS)

A line-scanning instrument carried by Landsat satellites that continually scans the Earth in a 185 km swath and collects data over a variety of wavelengths.  

For more information, see Landsat: Multispectral Scanner System.