Susan M. Hendrix

Goddard Space Flight Center Dec. 8, 1999

Office of Public Affairs

Greenbelt, MD

(Phone: 301-286-7745)

RELEASE NO: 99-131


NASA today announced selections of four investigations to be flown on the Solar TErrestrial RElations
Observatory (STEREO) mission, planned for launch in 2004. The STEREO mission will be a multilateral
international collaboration involving participants from France, Germany, the United States, and United Kingdom.
STEREO is the third mission selected for NASA’s Solar-Terrestrial Probe (STP) Program, under the Agency’s
Sun- Earth Connections Theme.

STEREO will for the first time unveil the Sun in three dimensions. Its objective is to address the origin,
evolution and interplanetary consequences of one the most massive disturbances in our solar system called the
coronal mass ejection (CME). This will be achieved by sending two identically instrumented spacecraft, both at 1
AU orbit around the Sun, but one flying well ahead of the Earth and one behind.

The instrument suite for STEREO will characterize the CME plasma all the way from the solar surface to the
orbit of the Earth. These instruments will measure physical characteristics of CME’s with remote sensing and
local sensing instruments, allowing scientists to determine solar origins of CME’s, their propagation into the
interplanetary medium and ultimately their consequences on Earth’s magnetic field.

By viewing CME’s in three dimensions, STEREO will be able to pinpoint their speed and distance from Earth, and
thus more accurately time the arrival of the plasma cloud. The planned 2004 launch date will enable STEREO to
make observations during the simpler, declining phase of the current activity cycle, which is expected to reach
solar maximum around the year 2000.

“Existing spacecraft only provide a limited picture of these huge solar eruptions, called CME’s, which can hurl
up to ten billion tons of electrically charged gas toward Earth at more than one million miles per hour,” said
STEREO co-investigator Dr. Barbara Thompson of NASA’s Goddard Space Flight Center (Greenbelt, MD). “By
placing two spacecraft off the Sun-Earth line, STEREO will reveal details about CME structure and dynamics that
have been impossible to obtain.”

The investigations selected by NASA are:

* Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) has four instruments: an Extreme
Ultraviolet Imager, two white-light coronagraphs and a Heliospheric Imager. SECCHI’s integrated instruments
will study the 3-D evolution of CME’s from birth at the Sun’s surface through the corona and interplanetary
medium to its eventual impact at Earth. Dr. Russell Howard, Naval Research Laboratory, Washington, D.C., will
lead this investigation.

* STEREO/WAVES (SWAVES) is an interplanetary radio burst tracker for STEREO that will track the generation
and evolution of traveling radio disturbances from the Sun to the orbit of Earth. Dr. Jean Louis H. Bougeret from
Centre National de la Recherche Space Scientifique Observatory of Paris and lead U.S. co-investigator, Dr.
Michael Kaiser of Goddard, will lead this investigation.

* In situ Measurements of Particles and CME Transients (IMPACT)
investigation will sample the 3-D distribution and provide plasma characteristics of solar energetic particles
and the local vector magnetic field. Dr. Janet G. Luhmann, University of California, Berkeley, will lead this

* PLAsma and SupraThermal Ion and Composition (PLASTIC) experiment will provide plasma characteristics of
protons, alpha particles and heavy ions. This experiment will provide key diagnostic measurements of the form
of mass and charge state composition of heavy ions and characterize the CME plasma from ambient coronal
plasma. Dr. Antoinette Galvin, University of New Hampshire, will lead this investigation.

“This selection forms the final link of a powerful partnership between the international science community,
NASA and Johns Hopkins University Applied Physics Laboratory,” said STEREO Mission Manager Abby Harper of
Goddard. “I am eager to work with such an experienced team, as STEREO will produce out-of-this-world class
science and space weather data for a relatively low cost.”

The two STEREO spacecraft will be built by Johns Hopkins University Applied Physics Laboratory (Laurel, Md.).
STEREO is a $150 million development mission (phase C/D real year cost), which equates to $64 million for
instruments and $86 million for the two spacecraft. Mission operations and data analysis cost is about $45
million. Development is scheduled to begin January 2001. Goddard will provide mission management and control

For additional information about the STEREO mission and its payload, go to: