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by Brad Wilson

We've become accustomed to timely and accurate weather forecasting. Developments in the late 20th Century in imaging and control systems enabled the use of satellites for global weather observation on a repeatable, regular time table.

The satellite hardware in use comes in two varieties, geostationary and polar orbiting. Geostationary satellites provide a big picture view of weather patterns over the same area on a regular schedule, every few minutes a picture can be transmitted. These geostationary satellites, while moving quickly through space, stay in one spot relative to the earth, and are spin stabilized like a gyroscope.

The other type of satellite is called a polar-orbiter and provides more detailed weather observations over a smaller geographic area. If you looked at a polar orbiter from the direction of the sun it would look like it is just moving in a circle while the earth spins beneath it, kind of like a classroom or library globe...you stand in one spot and the globe turns beneath you.

This trajectory allows the polar orbiting satellite to map the entire earth on a regular schedule since the satellite moves at a constant speed and the earth moves at a constant speed, the imagery is more detailed, consistent and reliable for weather observation.

The military uses these types of machines for weather observation, intelligence gathering and early warning of missile launches. While the technology is 50 years old it works reliably and is actually very effective. Sensors are made improved with technology advances and new satellites benefit from these advances.

Accurate weather forecasting would be extremely difficult without the detailed, reliable information these machines provide to our nation's meteorologists.

Barry's Response - Technological advances in the sensors. That's where we've seen most of our progress in the last few decades. Thanks for this description, Brad.




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