As a follow-up to the February 24, 2008 iTWire story “NASA announces retirement of legendary solar explorer: Ulysses,” officials with NASA report that: “After more than 17 years of pioneering solar science, a joint NASA and European Space Agency mission to study the sun will end on or about July 1.” [NASA: “International Mission Studying Sun to Conclude”]

The amazing spacecraft, which traveled over 5.4 billion miles, functioned for almost four times its expected lifespan.

In other words, the designers of Ulysses made it so the spacecraft would function nominally for about four years. Stubborn throughout its lifetime, the Ulysses spacecraft has continued to provide data to NASA and the European Space Agency (ESA) for over seventeen years.

It was launched on October 6, 1990, aboard the space shuttle Discovery, and for the NASA mission STS-41.

The reason for the Ulysses ending operations is a significant lack of power produced by its onboard radioisotope thermoelectric generators (RTGs). Power is produced by heat from the radioactive decay of plutonium-238.

The power generated is so low now that many of its critical internal heaters are unable to keep the spacecraft’s hydrazine, its attitude control fuel, from freezing. Soon, its hydrazine feed lines will freeze up, stopping all communications from the robotic spacecraft to humans on Earth.

NASA and ESA saw many important discoveries from its Ulysses spacecraft. Scientists say that the spacecraft “forever has changed the way scientists view the sun and its effect on the surrounding space.” [NASA]

Ed Smith, Ulysses project scientist at NASA's Jet Propulsion Laboratory, Pasadena, California, proudly stated, “The main objective of Ulysses was to study, from every angle, the heliosphere, which is the vast bubble in space carved out by the solar wind. Over its long life, Ulysses redefined our knowledge of the heliosphere and went on to answer questions about our solar neighborhood we did not know to ask." [NASA}

Another Ulysses scientist adds his comment. Please read on.