NASA announces retirement of legendary solar explorer: Ulysses

William Atkins
Saturday, 23 February 2008 20:36

Science - Space

On Friday, February 22, 2008, NASA announced that the Ulysses spacecraft will be soon retired after over seventeen years in space orbiting the Sun and going as far out as Jupiter. The remarkable space mission of Ulysses has provided Earth scientists with a galactic amount of data.       

The spacecraft Ulysses was launch in October 1990 from the space shuttle Discovery as part of the NASA STS-41 mission. It was supposed to last only five years in its mission. It has now far exceeded its intended lifetime.

Ulysses project manager, Ed Massey, at NASA’s Jet Propulsion Laboratory, comments on the beginning and the life of Ulysses, "I remember when we got those first pictures of Ulysses floating out of the space shuttle Discovery's payload bay back in October of 1990 and thinking we had a great five years ahead of us. I never dared think that we would be receiving invaluable science data on a near continuous basis for more than 17 years. Ulysses has set the bar on solar science data collection quite high." [NASA press release]

The NASA/European Space Agency (ESA) robotic space probe was designed to study the Sun from all latitudes, from its near-polar orbit about the Earth’s star, the Sun. The probe contains instruments to study various aspects of the Sun, from its magnetic fields, particles, and dust particles.

The spacecraft was named after the legendary explorer in Greek mythology, Ulysses (Odysseus), the hero of Homer’s poem, Odyssey.

The spacecraft operates with a radioisotope thermoelectric generator (RTG). However the radioactive isotope inside the RTG decays over time. Thus, the power in the RTG has been steadily decreasing over time. It is to the point that it cannot power the heaters enough to keep the probe’s hydrazine fuel from freezing. Once the fuel freezes (at about 36 degrees Fahrenheit) the space probe will cease to function.

The accomplishments of Ulysses is enormous. Some of these accomplishments are stated on the ESA website: “Ulysses has conducted the first-ever survey of the Sun's environment in space from the equator to the poles, and over a wide range of solar activity conditions. Key results to date include the first detailed measurements of the solar wind from the Sun's polar regions at solar minimum and solar maximum, the discovery that the magnetic flux leaving the Sun is the same at all latitudes, the discovery of energetic particle ‘reservoirs’ surrounding the Sun, the discovery of interstellar dust in the solar system, and the first direct measurements of interstellar helium atoms in the solar system.”

The Earth is a better informed planet and the citizens of Earth are better off because of the job performed and soon to be completed by Ulysses.

NASA, ESA, and the many contractors that helped to design, build, and operate Ulysses for these many years should be commended for the good work they are doing in the betterment of humankind: for the increased knowledge of the Sun is essential for our life here on Earth.

For more information on the Ulysses space probe, please read the NASA press release “International Solar Mission to End Following Stellar Performance”

Additional information about the NASA/ESA Ulysses mission is available at: http://ulysses.jpl.nasa.gov and http://ulysses.esa.int/science-e/www/area/index.cfm?fareaid=11.