Paula Cleggett-Haleim
Headquarters, Washington, D.C.                                                
August 23, 1993
Phone:  202/358-0883

Jim Wilson
Jet Propulsion Laboratory, Pasadena, Calif.
Phone:  818/354-5011


RELEASE:  93-149

HEADING FOR JUPITER, GALILEO TO ENCOUNTER ITS SECOND ASTEROID 

   NASA's Galileo spacecraft will encounter its second asteroid, 
called Ida, Saturday morning, Aug. 28, on Galileo's flight to 
explore Jupiter.  Galileo made the world's first asteroid 
encounter -- with Gaspra -- in October 1991.  

   At 12:52 p.m. EDT, Galileo will race through a closest approach 
distance of 1,500 miles (2,400 kilometers) from Ida.  Relative 
speed between Galileo and Ida will be almost 28,000 miles per hour 
(12.4 kilometers per second).  Radio signals confirming the 
encounter will reach mission controllers at NASA's Jet Propulsion 
Laboratory, Pasadena, Calif., 30 minutes later.    

   Galileo's camera and other scientific instruments will record 
observations from several hours before to several minutes after 
the closest point of approach to Ida.  Because Galileo must use 
its low-gain antenna for all communications, the pictures and 
other data will be played back, slowly, in September and in the 
spring of 1994.  

   "However," Project Manager William J. O'Neil said, "we will 
have a data set as good as the Gaspra encounter -- or even 
better."  

   Ida is a stony body, irregular in shape and about 20 miles (31 
kilometers) long.  Ida is larger than Gaspra and orbits farther 
from the Sun.  Ida is believed to belong to the same asteroid type 
as Gaspra, though Ida is younger and of slightly different 
composition.

   Galileo will reach Jupiter in December 1995 to study its 
satellites and its magnetosphere, using an atmospheric probe and 
an orbiter scheduled for a 10-orbit, 23-month survey.  
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