remote sensing

Getting the Big Picture: Remote Sensing

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A brief animated look at the different types of remote sensing techniques that NASA uses to study the Earth. This video discusses why we need remote sensing to study the Earth, and the differences between active and passive remote sensing from satellites. It also gives examples of different types of data NASA satellites collect about the Earth, and some of the applications of that data.

This video is public domain and can be downloaded in high resolution here.


GPM: Too Much, Too Little

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Researchers need accurate and timely rainfall information to better understand and model where and when severe floods, frequent landslides and devastating droughts may occur. GPM’s global rainfall data will help to better prepare and respond to a wide range of natural disasters.

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Dalia: GPM will help us to understand precipitation extremes. And this is everything from too much rainfall, such as flooding in India or Southeast Asia, to too little rainfall such as drought in the U.S. Southwest.

GCPEx: Measuring Frozen Precipitation from Space

Frozen precipitation is particularly difficult to measure from space due to the wide variability in snowflake shapes and behavior. Snowflakes can have different impacts on the active and passive instruments signals compared to liquid precipitation, which is further complicated by a weak signal to noise ratio resulting from different scattering properties of liquid verses frozen precipitation.

Active and Passive Remote Sensing Diagram

Diagram illustrating the differences between active and passive remote sensing.
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This diagram illustrates the differences between active and passive remote sensing.

TRMM and GPM rely on active and passive instruments to measure the properties of precipitation from space.

Active radars, such as the TRMM Precipitation Radar, transmit and receive signals reflected back to the radar. The signal returned to the radar receiver (called radar reflectivity) provides a measure of the size and number of rain/snow drops at multiple vertical layers in the cloud (Left figure).

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