iTWire - NASA and ESA Ulysses spacecraft flies past Sun’s hidden South Pole

NASA and ESA Ulysses spacecraft flies past Sun’s hidden South Pole

by William Atkins

Thursday, 08 February 2007

On February 7, 2007, the Ulysses spacecraft is traveling where almost all other spacecraft have never ventured: to the South Pole of the Sun. With only two other brief flybys of the Sun’s south polar cap, Ulysses has discovered an interesting and unusual place on the Sun.

In fact, NASA solar physicist Arik Posner states, “The sun’s south pole is uncharted territory. We can barely see it from Earth, and most of our sun-studying spacecraft are stationed over the sun’s equator with a poor view of higher latitudes.”

A joint mission by the United States (U.S.) National Aeronautics and Space Administration (NASA) and the European Union (E.U.) European Space Agency (ESA), the Ulysses unmanned space probe has a heliocentric orbit (one about the Sun) that reaches a latitude (an imaginary line that runs parallel to the Sun’s equator) of 80 degrees south, which is almost directly above the Sun’s South Pole.

Ulysses was launched in October 1990 by the astronaut crew aboard NASA’s Space Shuttle Discovery during mission STS-41. It was designed to explore all latitudes of the Sun with scientific instruments that look at various physical aspects of the Sun including its magnetic field and particles.

Ulysses has flown over the Sun’s South Pole only in 1994-1995 and 2000-2001. However, during those encounters, the spacecraft returned data that described interesting details of the Sun’s magnetic north pole, which is located at the South Pole—actually the same situation that currently occurs on the Earth. The Sun flips its magnetic poles every eleven years in unison with sunspot activity, while the Earth flips its poles only about every 300,000 years. Scientists do not know why the Earth changes its magnetic poles, so information gleaned from Ulysses may help to find the answer to this question.

The space probe Ulysses has also observed holes in the Sun’s magnetic field that lets out fast-moving solar wind. These so-called ‘coronal holes’ are comprised of extremely hot protons and electrons traveling outward at millions of miles an hour.

Ulysses has also discovered that the temperature at the northern and southern polar regions of the Sun are different. Why this occurs is a mystery to scientists. But, with a 2008 flyby of the North Pole by the spacecraft, that question will be researched further.

Ulysses' mission will probably end after its 2008 North Pole flyby of the Sun. The probe’s power generator—radioisotope thermoelectric generator (RTG)—will probably not have enough power to keep the probe functioning much after that time.

The NASA Ulysses Web site is: http://ulysses.jpl.nasa.gov/.

The ESA Ulysses Web site is: http://ulysses.esa.int/science-e/www/area/index.cfm?fareaid=11.

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