Humans are born with built-in remote sensing equipment: With our eyes, ears, and noses, we gather information about far-away objects. When we look at a tree and judge its health based on the number and colors of its leaves, we are performing a sort of spectral analysis. The three types of cone cells in the human eye sense light in three spectral bands; the mantis shrimp, with its 16 types of cones, sees, in principle, much more.
Similarly, a digital camera senses three bands, whereas NASA’s Terra and Aqua satellites each carry an instrument called MODIS (Moderate Resolution Imaging Spectroradiometer) that views Earth in 36 bands. The bands sample a spectral region (405 nm–14.4 μm) that ranges from the visible well into the long-wavelength IR. Data from those instruments help researchers to monitor the oceans and land and categorize Earth’s surface into 17 broad classes—for example, savannahs, croplands, and water—frequently...
