Weather 101: Weather Satellites

    6:56 PM, Apr 1, 2010   |    comments
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    Since 1960, weather satellites have not only enabled those in the path of hurricanes to evacuate safely, they have provided large amounts of data about our planet and climate. Satellites can even tell us the sea surface temperature to within one degree Celsius.

    The first weather satellite, VANGUARD 2, was launched on February 17, 1959 with unsuccessful results. The first satellite to be considered a success was TIROS-1, launched by NASA on April 1, 1960. 50 years of advancements have now led to a network of American, European, Japanese and Russian satellites orbiting the earth in various configurations to provide real time monitoring of our environment.

    Satellites orbit the earth in two different ways. Geostationary (GOES) satellites orbit the earth over the equator at an altitude of 22 thousand miles. Because of this orbit altitude, they remain stationary with respect to the rotating earth. GOES Satellites are what we use on the weather cast each night.

    Polar Orbiting Satellites are the main source for environmental data for the 80% of the globe that is not covered by conventional monitoring equipment.

    These satellites make measurements of temperature and humidity in the Earth's atmosphere, record surface ground and sea water temperatures, and monitor cloud cover and water/ice boundries. Polar orbiting satellites have orbits that cross very close to the poles on each revolution of the earth.

    At an altitude of 500 miles, the sensors scan the entire surface of the earth over a 24-hour period. Polar satellites orbit in a North-South path in a sun-synchronous orbit, which means they move with the same general lighting conditions to a near-constant local solar time.

    These satellites offer a much better resolution than their GOES counterparts due to their closeness to the earth.

    There are two types of images or channels satellites use.

    The Visible Spectrum

    Visible light images during local daylight hours show clouds and land from the light of the sun. In other words, it's what you would see if you were looking down on the sunlit earth from 22 thousand miles at space.

    The Infrared Spectrum

    This is how we see clouds at night. Infrared technology shows us the clouds based on temperature. Sensors called scanning radiometers enable operators to determine cloud heights and types, calculate land and surface water temperatures.

    The greatest advantage of having a GOES satellite with both visible and infrared capability is that weather systems can be monitored both day and night at 30 minute intervals. Satellite loops or movies are an animation of as many single images as needed.

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