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GRAS description
| Flown on MetOp, the new GRAS (Global Navigation Satellite System Receiver for Atmospheric Sounding) instrument will, through the technique of radio occultation, provide very accurate information about the temperature and humidity in the atmosphere for use in weather forecasting and climate change monitoring.
Credits: ESA - AOES Medialab | |  |  | |
| | | | | | A schematic of atmospheric profiling by GPS radio occultation. An occultation occurs whenever a GPS satellite rises or sets on the Earth limbs as seen from the Low Earth orbit (LEO) satellite. The GPS signal is refracted and slowed as it traverses the Earth’s atmospheric limb. This causes a phase delay that relates to characteristics of the Earth's atmosphere. | | | | |
| | | | | | Depending on the geometry of the orbits of the transmitter and receiver,occultations will have different shapes ranging from short to long duration. | | | | |
| | | | Last update: 28 June 2006 | |
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