Paula Cleggett-Haleim
Headquarters, Washington, D.C.                         May 28, 1991
(Phone:  202/453-1549)

Robert MacMillin
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone:  818/354-5011) 


RELEASE:  91-82

ULYSSES TO BEGIN JUPITER PHYSICS INVESTIGATIONS


	Science teams on the Ulysses mission to the poles of the 
sun are preparing to begin physics investigations during the 
forthcoming encounter with Jupiter, European Space Agency 
(ESA) and NASA Jet Propulsion Laborator (JPL), Pasadena, Calif., 
project officials reported Tuesday.

	Ulysses' science objectives at Jupiter and recent scientific 
results were reviewed by Drs. Edward J. Smith of JPL and Klaus-
Peter Wenzel of the European Space Research and Technology 
Centre (ESTEC) at the 1991 Spring Meeting of the American 
Geophysical Union in Baltimore, Md.  Smith and Wenzel are the 
NASA and European project scientists, respectively, for the joint 
NASA-ESA mission.

	The Ulysses spacecraft is currently traveling in the ecliptic 
plane -- the plane in which the planets of the solar system orbit 
the sun -- on a trajectory that will use the gravity of Jupiter to 
deflect Ulysses out of the ecliptic plane and onward to the polar 
regions of the sun.  

	The 809-pound spacecraft is expected to reach the Jovian 
giant and its system of satellites on Feb. 8, 1992.  Once there, 
Ulysses will make measurements of the Jovian magnetosphere 
during a 2-week sweep past the planet, said Dr. Edgar Page of the 
ESA Space Science Department.

	The encounter will yield new information on the 
magnetosphere of Jupiter, its interaction with the solar wind and 
the composition of energetic particles and positively charged 
atoms (ions) in the region influenced by the planet.

	The spacecraft will fly past Jupiter at about 30 degrees 
north Jovian latitude, said JPL Ulysses Project Manager Willis 
Meeks.  At nearest approach, Ulysses will pass the planet at 
approximately 6.3 Jupiter radii -- 450,480 kilometers or about 
279,300 miles -- from the center.

	Immediately after encounter, the spacecraft will be in "solar 
opposition," so that Earth is directly between the sun and the 
spacecraft.  Scientists will use the spacecraft's radio transmitters 
to search for gravitational waves.

	From there, Ulysses will use the extra acceleration gained 
from the gravitational pull of Jupiter to swing itself out of the 
ecliptic plane and onward to the southern solar pole.  In 
June1994, Ulysses will reach 70 degrees south solar latitude and 
begin its primary mission of exploring the polar regions of the sun 
and space above the poles.  At closest approach, Ulysses will travel 
within 1.3 astronomical units or about 120 million miles of the 
sun.

	Ulysses is a 5-year mission managed jointly by NASA and the 
European Space Agency.  ESA provided the spacecraft, half the 
science instruments, ground control computer system and 
spacecraft control personnel.  NASA provided the launch vehicle, 
the power supply and the other half of the onboard science 
instruments.  Tracking and data collection during the mission are 
being provided by NASA's Deep Space Network, managed by JPL.