What would it be like to sit out in space and look down on the Earth with special UV glasses? Well, if you can't do that, what if you could send up a camera that could take UV pictures and send them back to us? NASA's Ultraviolet Imager is just the camera that can do that. It was launched in February 1996. This is the most recent picture made with the Ultraviolet Imager. It is updated about every 7 minutes when the Polar spacecraft is in contact with the Earth. Its main job is to make pictures in the UV of the aurora, or sometimes called the northern and southern lights. Because of special filters, the glare of the bright Sun is not a problem and the aurora can be seen both on the night and day side of the Earth.

The filters used in the UVI block the visible reflection of the sun off the Earth's surface so that only the ultraviolet wavelengths are imaged. When the activity of the aurora is low, we don't see much and the images tend to be blue/red. When the activity is high, the auroral oval is bright gold or white and usually dynamic. The bright features result from energy being deposited in the Earth's atmosphere about 100-150 km up in the form of energetic electrons. These electrons collide with the Earth's atmosphere, which excite its constituents (primarily molecular nitrogen and atomic oxygen). The excited molecules or atoms release the energy in the form of light. The UVI detects the ultraviolet emitted light. The time is the Universal Time. Subtract 6 hours to get Central Standard Time.