A constellation of thermometers.With an eye toward improving weather predictions, scientists have developed an efficient way of gauging atmospheric temperatures around the globe with a fleet of orbiting satellites. The constellation of 24 Global Positioning System Global Positioning System: see navigation satellite. Global Positioning System (GPS) Precise satellite-based navigation and location system originally developed for U.S. military use. (GPS) satellites is best known as a locating tool. The satellites send out signals that can be picked up with a handheld receiver by a person on the ground. By triangulating from three or more satellites, a receiver can pinpoint its position with extreme accuracy. Last year, researchers at NASA's Jet Propulsion Laboratory “JPL” redirects here. For other uses, see JPL (disambiguation). Jet Propulsion Laboratory (JPL) is a NASA research center located in the cities of Pasadena and La Cañada Flintridge, near Los Angeles, California, USA. (JPL (language) JPL - JAM Programming Language. ) in Pasadena, Calif., conducted an experiment to test other uses of the positioning satellites. They flew a GPS receiver onboard a new satellite launched into a low orbit around Earth. From t his vantage, the receiver can pick up signals from distant GPS satellites as they disappear behind the planet and emerge from the other side. Such occultation occultation (ŏk'əltā`shən), in astronomy, eclipse of one celestial body by another, e.g., when the moon lies between a star and the earth. Occultations of stars by the moon are important in astronomy. measurements provide a way of sensing the atmosphere's temperature. As the GPS radio signals graze the planet, they pass briefly through the atmosphere. The air acts as a giant lens, bending the radio waves Radio waves Electromagnetic energy of the frequency range corresponding to that used in radio communications, usually 10,000 cycles per second to 300 billion cycles per second. . The amount of bending, or refraction refraction, in physics, deflection of a wave on passing obliquely from one transparent medium into a second medium in which its speed is different, as the passage of a light ray from air into glass. , depends on the temperature of the air and how much water vapor it holds. In cold parts of the atmosphere, which are extremely dry, the refraction provides an accurate measurement of the temperature. In the Feb. 23 Science, E. Robert Kursinski of JPL and his colleagues compare the GPS occultation measurements to temperatures taken with routine balloon launches. At high latitudes, the satellite technique matched balloon measurements to within 1#161#C. In warmer climes, moisture in the air hindered temperature measurements near the ground, but the satellite technique worked well above 10 kilometers in altitude. This accuracy surpasses that of routine satellite sensors, which measure atmospheric temperat ure by reading infrared or microwave radiation emitted by air molecules. A group of similar orbiting receivers would significantly expand the geographic distribution of temperature measurements and improve weather prediction, the scientists claim. But the GPS system faces some competition. In the next several years, NASA NASA: see National Aeronautics and Space Administration. NASA in full National Aeronautics and Space Administration Independent U.S. plans to test other space techniques for measuring atmospheric temperature. |
|
||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion