Douglas Isbell
Headquarters, Washington, DC                                     March 10, 1995
(Phone:  202/358-1753)

Diane Ainsworth
Jet Propulsion Laboratory, Pasadena, CA
(Phone:  818/354-5011)

RELEASE:  95-26

ULYSSES SPACECRAFT TO MAKE CLOSEST APPROACH TO SUN

     The Ulysses spacecraft will pass within 124 million miles (200 million 
kilometers) of the Sun at 3:40 a.m. Pacific Standard Time (11:40 Universal Time), 
March 12, the closest it has ever been or ever will be to the Sun since it was 
launched on October 6, 1990.

     Its distance from Earth at perihelion, or closest approach to the Sun, will 
be approximately 215 million miles (346 million kilometers), said Donald Meyer, 
Ulysses deputy mission operations manager at NASA's Jet Propulsion Laboratory 
(JPL), Pasadena, CA. 

     Ulysses is crossing rapidly into the Sun's northern hemisphere, traveling at 
a rate of about 0.8 degrees in solar latitude per day and a velocity of 
approximately 73,000 miles per hour (117,000 kilometers per hour) with respect to 
the Sun.

     For the last month the spacecraft has been collecting data on the equatorial 
region of the Sun.  This effort will continue for the next month, until Ulysses 
begins to see features from the northern hemisphere of the Sun, said Peter Beech, 
Ulysses mission operations manager for the European Space Agency (ESA).

     All spacecraft operations and science experiments continue to go well.  A 
radio science experiment is currently underway to measure the electron content of 
the Sun's fiery outer atmosphere, called the corona, as Ulysses passes in back of 
the Sun as seen from Earth.

     The spacecraft's S-band transmitter was turned on February 22 to take 
advantage of Ulysses' unique position in space to conduct the radio experiment. 
This transmitter, in conjunction with the X-band transmitter, will be beaming 
signals through the corona to provide measurements of the electron content 
through March 15.


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     As Ulysses crosses into the northern hemisphere of the heliosphere -- the 
region of space dominated by the forces of the solar wind -- it will begin its 
next phase of the primary mission to study that region at all solar latitudes.  
This phase will be highlighted when Ulysses reaches 70 degrees north of the Sun's 
equator in June and begins a four-month pass over a second region of the Sun 
never before explored, as it did with the Sun's southern hemisphere.

     During earlier phases of the mission, Ulysses mission scientists found that 
the solar wind in the Sun's polar regions flows at about two million miles per 
hour (750 kilometers per second), nearly twice the velocity measured at lower 
solar latitudes.  They also reported that cosmic ray intensity at high latitudes 
increased, but not nearly to the extent predicted.

     The Ulysses mission, managed jointly by NASA and ESA, was designed to study 
the regions above the Sun's poles.  JPL manages the U.S. portion of the mission 
for NASA's Office of Space Science, Washington, DC.

                                       - end -

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