Solar wind dropping, says ESA

Stephen Withers
Wednesday, 24 September 2008 08:46

Science - Space

Even time spent in relatively low orbits has been shown to cause damage to chromosomes, though it seems largely reversible. A short trip to the Moon is one thing (though former Apollo astronauts reportedly have a high incidence of cataracts, thought to be caused by cosmic rays), but a multi-year voyage to Mars would result in significant exposure to cosmic rays unless the craft was more heavily shielded than its predecessors.

A US FAA study concluded that 10 percent of men and 17 percent of women taking such a trip to Mars would be likely to develop fatal cancers in later life. This is substantially greater than the 3 percent career risk for astronauts recommended by the US National Council on Radiation Protection and Measurement.

The solar wind measurements may be among the last recorded by Ulysses, which is in a polar orbit around the Sun.

Launched from the Space Shuttle Discovery in 1990, Ulysses has functioned for almost four times longer than its original mission. Although it was expected to finally cease operation in July 2008, it is still operating two months later.

The fuel needed to keep the antenna pointing towards Earth will eventually freeze, bringing the mission to an end.

The craft was built by Dornier Systems of Germany (now Astrium), and powered by a radioisotope thermoelectric generator from the US Department of Energy.

"Even though the end is now in sight, every day's worth of new data is adding to our knowledge of the Sun and its environment," said Richard Marsden, ESA's Ulysses project scientist and mission manager.