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Ulysses Spacecraft Swoops Under Sun
Pasadena CA (JPL) Feb 07, 2007 The 16-year-old Ulysses spacecraft reaches what could be considered a low point in its mission observing the sun today - and solar scientists could not be happier. The European-manufactured, joint NASA- and ESA-managed spacecraft, has reached maximum latitude in its exploration of the heliosphere, the bubble in space blown out by the solar wind. "At max latitude we are actually passing below the sun looking almost directly up at its south pole from 329 million kilometers (204 million miles) away," said Nigel Angold, Ulysses mission operations manager from the European Space Agency. "The trajectory provides a perspective of the sun no other spacecraft can equal." This unusual perspective is courtesy of the spacecraft's one-of-its-kind 6.3-year-long orbit around the sun. An orbit that swings Ulysses both over and under the sun's polar regions and as far out as the orbit of Jupiter. "Max latitude is the start of an important mission phase," said Dr. Ed Smith, Ulysses project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The spacecraft will soon begin accelerating as it transits from below the sun's south pole to its equator and then up and over its north pole. This trajectory provides us a ringside seat to all the solar processes we want to observe." This phase of the mission is expected to return high priority scientific observations revealing the changing sun and its effect on space during the ongoing minimum in the 11-year sunspot cycle. During this portion of the mission, Ulysses will rapidly scan the sun's magnetic field, solar plasmas, solar radio noise, energetic particles, galactic cosmic rays and cosmic dust between the poles and the equator - imparting a more complete perspective of the sun's atmosphere. Understanding the Earth's nearest star and its processes is paramount, as the space weather created by the sun has a huge effect on the third rock from it and its inhabitants. The sun's gaseous outer atmosphere can create huge space storms. This violent space weather, in turn, can affect Earth's electrical grid, cell phone communications, the functioning of satellites and the operation of astronauts in orbit. This passage between the sun's poles is the third in the 17 years of Ulysses operations. The first transit occurred during the previous sunspot minimum in 1994 to 1995, and the second during sunspot maximum in 2000 to 2001. The opportunity to repeat the scientific investigations during the ongoing solar minimum is important because the sun's magnetic field has changed significantly since the previous minimum.
earlier related report Launched in 1990, the European-built spacecraft visits both polar regions once every 6.2 years as it circles the Sun in an orbit that is almost perpendicular to the ecliptic, the plane in which the Earth and the planets move. Although originally designed for a mission lasting 5 years, the Ulysses space probe and its suite of 9 scientific experiments are still going strong after more than 16 years in orbit. Operating the spacecraft has become more demanding over the years, however, as one consequence of the mission's longevity is a decrease in the electrical power available on board. "Ulysses uses a Radioisotope Thermoelectric Generator, or RTG for short, to generate the electricity needed for the spacecraft subsystems and science instruments", said Nigel Angold, ESA's Mission Operations Manager for Ulysses. The RTG converts the heat produced by radioactive decay of its fuel into electrical power. "As a result of the decay process, the RTG output decreases with time", said Angold. In recent years, this has necessitated sharing the available power among the science instruments in such a way that key instruments are kept on permanently, while others are operated only part of the time. Starting in May, as Ulysses comes closer to the Sun, one of the power-hungry heaters on board the spacecraft will be switched off. "This will free up sufficient power to have the full suite of instruments switched on during a key phase of the mission, the rapid transit from the south to the Sun's north polar cap", said Richard Marsden, ESA's Ulysses Project Scientist and Mission Manager. Related Links Ulysses at JPL Ulysses at ESA Solar Science News at SpaceDaily Solar Science News at SpaceDaily
South Polar Flyby
Washington DC (SPX) Feb 08, 2007Less than one hundred years ago, the south pole of Earth was a land of utter mystery. Explorers labored mightily to get there, fighting scurvy, wind, disorientation and a fantastic almost-martian cold. Until Roald Amundsen and Robert F. Scott reached the Pole in 1911 and 1912, it was terra incognita. |
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