The Ulysses spacecraft -- the first probe to explore the sun's environment at high latitudes -- has completed its pass over the southern solar pole, finishing the first phase of its primary mission, members of the mission operations team at the Jet Propulsion Laboratory have reported.
The spacecraft reached 70 degrees south of the sun's equator at noon Pacific Standard Time on Nov. 5, crossing back into what scientists have defined as a lower latitude region of the sun's environment. Just as the Arctic Circle on Earth lies at about 67 degrees north of the Earth's equator, so too have the polar regions of the sun been theoretically defined as lying about 70 degrees north and south of the sun's equator.
As the spacecraft left an area of high scientific interest, project scientists have reported some early findings, including the following:
-- In the polar regions, the solar wind -- a very hot, ionized flow of gases and energetic particles emanating from the sun -- was found to be flowing at a very high velocity of about 750 kilometers per second (about 2 million miles per hour), nearly double the speed at which the solar wind is known to flow at lower latitudes.
-- The way that Ulysses sees the sun's magnetic field is very different from the way it is seen by observations from Earth. Measurements from Earth show the sun having a magnetic field with magnetic poles that are not the same as the sun's north and south poles; as the sun rotates, the magnetic poles go around. Ulysses, however, found a uniform magnetic field at the sun and did not detect any magnetic poles.
-- Cosmic ray intensity in this high latitude region increased, but not nearly to the extent that scientists had predicted.
Over the next four months, Ulysses will be heading back toward the sun's equator, where it will make its closest approach of about 1.3 astronomical units (192 million kilometers or 120 million miles) on March 12, 1995. At that time scientists plan to conduct a "coronal sounding" experiment in which they will use the spacecraft's radio beam to measure the electron content of the sun's corona. Ulysses will then continue its northern ascent to traverse the sun's northern pole beginning on June 19, 1995.
Ulysses is managed jointly by NASA and the European Space Agency to study the regions above the sun's poles. The Jet Propulsion Laboratory manages the U.S. portion of the mission for NASA's Office of Space Science, Washington, D.C.
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