Dolores Beasley

Headquarters, Washington, DC

(Phone: 202/358-1753)

Susan Hendrix

Goddard Space Flight Center, Greenbelt, MD

(Phone: 301/286-7745)

RELEASE: 00-105

An international collaboration will investigate a struggle
that’s raging in space — a turbulent battle between the Earth’s
magnetic field and a solar wind blowing about one to two million
miles per hour. Four satellites, flying in formation, will be
used to examine this complex interaction between the Earth and the

It all begins with the first of two launches of the European
Space Agency’s (ESA) Cluster spacecraft. The first launch is set
for July 15 at 8:43 a.m. EDT in Baikonur, Kazakhstan. Two
satellites will be carried into orbit by a Russian Soyuz rocket.
A second pair is scheduled to launch August 9.

“Cluster is just one example of the marvelous and
sophisticated space exploration fleets that can be outfitted
through the unselfish cooperation between ESA and NASA,” said
Larry Christensen, Cluster project manager at NASA’s Goddard Space
Flight Center, Greenbelt, MD.

During its two-year mission, the quartet of satellites will
travel around the Earth in a tetrahedral — or triangular pyramid
— formation, collecting data where the solar wind, which is a gas
comprised primarily of electrons and protons, impacts the Earth’s
magnetic field. The unprecedented detail provided by Cluster will
allow scientists to assemble the first thorough three-dimensional
maps of the environment that surrounds and protects our planet.

Each spacecraft will carry the following complement of 11
identical instruments:

  • Active Spacecraft Potential Control (ASPOC) — will reduce
    the electric charge on the spacecraft, so very low-speed electrons
    can be measured. (Austria)

  • Cluster Ion Spectrometry (CIS) — will measure the relative
    abundance of protons and helium nuclei and determine their three-
    dimensional distribution in the solar wind and magnetosphere.

  • Digital Wave Processor (DWP) — will provide data processing
    for the plasma wave instruments. (Great Britain)

  • Electron Drift Instrument (EDI) — will determine strength
    and direction of the ambient electric field. (Germany)

  • Electric Fields and Waves (EFW) — will measure fluctuating
    electric fields in the plasma surrounding the spacecraft. (Sweden)

  • Fluxgate Magnetometer (FGM) — will measure static and
    fluctuating magnetic fields at the spacecraft. (Great Britain)

  • Plasma Electron and Current Experiment (PEACE) — will
    provide three-dimensional measurements of electron distributions
    in the solar wind and magnetosphere. (Great Britain)

  • Research with Adaptive Particle Imaging Detectors (RAPID) —
    will measure energetic ions and electrons. (Germany)

  • Spatio-Temporal Analysis of Field Fluctuations (STAFF) —
    will measure high frequency waves in the local plasma. (France)

  • Wideband (WBD) Plasma Wave Investigation — will detect very
    high-frequency plasma waves at very high time-resolution. (U.S. –
    – University of Iowa)

  • Waves of High Frequency and Sounder for Probing of Density by
    Relaxation (WHISPER) — will use high-frequency plasma waves to
    probe surrounding plasma to determine the local density of charged
    particles. (France)

The current Cluster mission replaces the original spacecraft,
which were lost in 1996 shortly after liftoff.

“Instruments aboard Cluster will provide the only 3-D fast
diagnostic tool for studying the Sun-Earth connection and entry of
plasma into the magnetosphere,” said Dino Machi, Cluster program
manager at Goddard. “The mission is extremely important because
particularly energetic particles can have a dramatic effect on
human activities, disrupting electrical power and
telecommunications or causing serious anomalies in satellite
operations, especially those in geostationary orbit.”

Cluster will join the Solar and Heliospheric Observatory
(SOHO), launched in December 1995, as the second cooperative
solar-terrestrial project between ESA and NASA. NASA will provide
project management and funding for the U.S. principal investigator
and U.S. co-investigator hardware investigations, assist ESA with
launch and early operations support, provide scheduling support
and transmit WBD data from Cluster to the University of Iowa via
the Agency’s Deep Space Network.

More information on this mission can be found on the
following Internet web sites:

and (Live launch webcast by ESA)