GPS Limb Sounding

Scientists at the Jet Propulsion Laboratory have found they can use orbiting Global Positioning System or GPS satellites to monitor weather.

In the same way that light bends, or refracts as it enters water, the radio signals from these satellites are refracted as they pass through the atmosphere. By skimming radio signals between two satellites, profiles of the atmosphere can be created. It’s a technique called limb sounding.

Tom Yunck is a researcher at the Jet Propulsion Laboratory. Limb sounding works well, he says, because it’s a very simple measurement based only on timing of the signal arrival.

Tom Yunck: By observing the precise time delay of the signal… we can determine the bending angle of the signal, from which we then get the density, pressure, temperature, moisture, and we can process that data further to determine the stratospheric and tropospheric winds, that is winds in the lower and upper atmosphere.

These stratospheric winds affect airline routes and can sometimes create hazardous conditions. And besides weather prediction and climate research, limb sounding might also be used to create the first 3-D images of Earth’s ionosphere. That’s the curtain of charged particles that set the stage for the shimmering aurora borealis.

NASA Brings New Earth Monitoring Technology To Light (May 14, 2002 – Jet Propulsion Laboratory)

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