Ultraviolet Imager (UVI)
The Ultraviolet Imager (UVI) is a small sophisticated camera, which from Earth orbit, will detect and produce images of the ultraviolet light of the aurora, day and night. As such, it is one of eleven instruments onboard the Polar spacecraft, which is part of the International Solar Terrestrial Physics (ISTP) Program.
The UVI is able to detect and provide images of very dim emissions with a wavelength resolution never achievable before. The highly sensitive instrument will conduct observations of the polar aurora in the far ultraviolet wavelengths and help quantify the overall effects of solar energy input to the Earth's polar regions. Its scientific objectives are to image the aurora simultaneously, to measure the total energy and characterize the energy that is deposited in the auroral regions, to characterize the space and time variations of the aurora, and to correlate events in the auroral regions to other regions in the magnetosphere.
Energetic particles, including electrons and protons, emanate from the Sun comprising what is called the solar wind. As these particles stream by the Earth at speeds up to one million miles per hour, they are redistributed and accelerated by the Earth's magnetic field in a region of space known as the magnetosphere. This redistribution of solar energy results in channeling large amounts of energy, equivalent to as much as 100 million kilowatts of energy each day, down into the Earth's atmosphere in the polar regions. These energetic particles collide with the elements of the upper atmosphere at altitudes between 90 and 150 kilometers resulting in the emission of light known as the aurora. The aurora can be thought of as the "footprint" of events and energetic processes occurring in the Earth's magnetosphere.
The objective of ISTP is primarily three fold: To measure the energy and particle flow from the Sun into the Earth's magnetosphere and atmosphere and how the flow changes in time; To improve the understanding of the processes that determine this flow; and To determine the importance of the variations of this flow to the Earth's atmosphere.
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