NASA's Polar Mission Ends with Broken Heart

After a mission of twelve years to study the Aurora Borealis phenomenon the Polar satellite has now produced its final image, "The Broken Heart", as NASA researchers named it, a visible-light photograph of the lights generated during the interactions between solar wind, Earth's magnetic field and the upper atmosphere. The Polar satellite was launched into space on February 24, 1996 and was originally scheduled for a two year mission.

"We've gone well beyond our original plan into our dreams", says John Sigwarth, NASA Goddard Space Flight Center investigator and project scientist for the Polar spacecraft. Polar has an orbit that takes it directly over the North and the South Pole, once every seventeen and a half hours. During this time it reaches a maximum altitude of 51,200 kilometers and a minimum of 5,120 kilometers.

The 12 instruments Polar carries on board include three cameras operating in the ultraviolet, X-ray and visible light spectrums. The rest of the instruments are designed to measure the charge of subatomic particles as well as Earth's electric and magnetic fields.

"Polar ran out of fuel during its final maneuver in February. But even after the fuel was exhausted, we continued to maneuver on the cold helium gas that was left in the tank", explains Sigwarth. Practically, since then the spacecraft has been drifting helplessly through space. Yesterday Polar was turned off, as it cannot conduct any further observations; solar radiation is slowly but certainly pushing it away from its current orbit, and in the long run it will most likely fall into the Sun.

Even if it were left to operate for a little longer, its systems would have probably overheated and eventually failed one at a time. During its mission Polar conducted investigations involving energetic neutral atoms and images of substorm injections determining energetic auroral displays, the energy dumped by solar storms in Earth's ionosphere and magnetosphere, X-ray images of auroral phenomena or solar wind dynamic pressure pulses. Alternatively, Polar had observed for the first time auroral ovals, rings of light above the planet's magnetic poles.