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AVIRIS Concept
The AVIRIS instrument contains 224 different detectors, each with a wavelength sensitive range (also known as spectral bandwidth) of approximately 10 nanometers (nm), allowing it to cover the entire range between 380 nm and 2500 nm. When the data from each detector is plotted on a graph, it yields a complete VIS-NIR-SWIR spectrum. Comparing the resulting spectrum with those of known substances reveals information about the composition of the area being viewed by the instrument.
Click image to see larger graphic
AVIRIS uses a scanning mirror to sweep back and forth ("whisk broom" fashion), producing 677 pixels for the 224 detectors each scan. The pixel size and swath width of the AVIRIS data depend on the altitude from which the data is collected. When collected by the ER-2 (20km above the ground) each pixel produced by the instrument covers an area approximately 20 meters diameter on the ground (with some overlap between pixels), thus yielding a ground swath about 11 kilometers wide. When collected by the Twin Otter (4km above the ground), each ground pixel is 4m square, and the swath is 2km wide.

The ground data is recorded on board the instrument along with navigation and engineering data and the readings from the AVIRIS on-board calibrator. When all of this data is processed and stored on the ground, it yields approximately 140 Megabytes (MB) for every 512 scans (or lines) of data. Each 512 line set of data is called a "scene", and corresponds to an area about 10km long on the ground.

Every time AVIRIS flies, the instrument takes several "runs" of data (also known as "flight lines"). A full AVIRIS disk can yield about 76 Gigabytes (GB) of data per day.




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Last Updated:
October 30, 2007

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