Dolores Beasley
Headquarters, Washington, DC           August 7, 2000
(Phone: 202/358-1753)

Susan Hendrix
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-7745)

RELEASE: 00-118

REVISED - SECOND CLUSTER LAUNCH TO COMPLETE ON ORBIT QUARTET

     The two remaining Cluster spacecraft, set to launch 
later this week, will rendezvous in mid-August with their two 
sister ships, creating a fleet that will explore a vast 
but invisible magnetic ocean that surrounds our Earth.

     This mysterious region we know as the magnetic field 
holds off a million mile-per-hour solar wind, and it's 
where million-amp electric currents surge and ignite a 
show seen as the northern and southern lights. 

     Lift-off for the second Cluster duo, named Rumba and 
Tango, is scheduled for 7:13 a.m. EDT on Wednesday, Aug. 
9, aboard a Russian Soyuz rocket from Baikonur, 
Kazakhstan. 

     "NASA and the U.S. scientific community are very 
excited and pleased with the first launch of Cluster 
spacecraft and eagerly await the second launch," said 
Larry Christensen, Cluster project manager at NASA's 
Goddard Space Flight Center, Greenbelt, MD. "This 
international mission will help us better understand a 
mysterious region of our space environment that can 
affect spacecraft and electrical power grids on Earth."

     The Earth's magnetic field, called the 
magnetosphere, is relentlessly blasted and energized by 
the solar wind, a stream of electrically charged 
particles that flows constantly from the Sun. During the 
next two years, as the solar wind buffets Earth's 
magnetic sea, the Cluster II fleet will penetrate its 
depths to see how the Earth's magnetosphere responds and 
interacts with solar wind particles. 

     By flying in a tetrahedral - or triangular pyramid- 
formation, the Cluster quartet will study the physical 
processes that take place between about 11,800 miles 
(19,000 km) and nearly 74,000 miles (119,000 km) above 
Earth, providing scientists with the first thorough 
three-dimensional maps of this shadowy realm.

     The first Cluster pair, called Samba and Salsa, 
launched July 16, reached their parking elliptical orbit 
on July 21 after a complex series of maneuvers. They 
await the arrival of the sister spacecraft, Rumba and 
Tango, to achieve their final observational orbit.

 The space quartet will orbit at an apogee of more than 
75,200 miles (121,098 km) and a perigee of nearly 10,500 
miles (16,869 km) above Earth.

     Cluster will join the Solar and Heliospheric 
Observatory (SOHO) as the second cooperative solar-
terrestrial project between NASA and the European Space 
Agency (ESA). In support of this ESA mission, NASA will 
provide project management and funding for the U.S. 
principal investigator and co-investigator hardware 
investigations, assist ESA managers with launch and early 
operations support, provide scheduling support, and 
transmit data from the Wide Band Data experiment on each 
spacecraft to the University of Iowa via NASA's Deep 
Space Network.

     For a listing of the instruments aboard Cluster, go 
to:

                  http://sci.esa.int/cluster/

     You also can view a live webcast of the Aug. 9 
launch from the ESA website at:

                   http://television.esa.int

                             - end -