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Sun-Earth Day Presents: Ancient Observatories, Timeless Knowledge

Technology Through Time: Issue #13, polar

The dazzling Northern Lights have enchanted humans for thousands of years. The Polar satellite's vantage point in space lets scientists admire and study the Earth's crowns of light, and learn their secrets.


The Polar spacecraft was launched on February 24, 1996. The satellite is in a highly elliptical orbit, with apogee at 57,000 kilometers and perigee at 11,000 kilometers. The inclination is 86 and the satellite takes about 18 hours to orbit Earth.


There are 12 instruments in total, with three sampling the electric and magnetic environment surrounding the spacecraft, six observing the electrically charged particles that make up the plasmas, and three cameras dedicated to imaging the aurora, the northern and southern lights in visible, ultraviolet and X-ray wavelengths. The most unique feature of Polar is that it carries a non-spinning platform to house the sophisticated imaging instruments. This may not sound very complicated at first until you realize that the main body of the spacecraft with the other instruments actually spins as it orbits the Earth. The spin allows the charged particle observing instruments to measure the plasmas at different angles with respect to the magnetic field, and to hold out by centrifugal force the very long wire antennas that are necessary measure the electric field. The engineers worked hard to implement this intricate idea and the end result was that scientists were then able to get high time and spatial resolution auroral images.


The Polar mission was designed to allow scientists to study many features of Earth's geospace - the huge region that surrounds our planet where electrically charged gases, or plasmas, are controlled by the Earth's magnetic field. Plasmas are composed of positively and negatively electrically charged particles occurring in equal numbers. Plasmas in geospace can originate from the sun or from our own planet.



Image Gallery:

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Photo Credit:


Related Polar Links


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Auroral Oval (1)

It wasn't until the Space Age, when satellites could gather images of the entire Earth, that scientists were able to see the large-scale auroras around both poles at the same time. (avi-9.85 MB)

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Auroral Oval (2)

Enjoy a second view of this amazing auroral phenomena. (avi-9.85 MB)

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