THEMIS Mission to Provide New Understanding of Substorm Life Cycle

Jan. 17, 2007

Dwayne Brown/Tabatha Thompson
Headquarters, Washington
202-358-1726/3895

Cynthia O'Carroll
Goddard Space Flight Center, Greenbelt, Md.
301-286-4647

RELEASE: 07-011

THEMIS MISSION TO PROVIDE NEW UNDERSTANDING OF SUBSTORM LIFE CYCLE

WASHINGTON - NASA's THEMIS, the Time History of Events and Macroscale
Interactions during Substorms mission, is set to venture into space
and help resolve the mystery of what triggers geomagnetic substorms.
For the first time, scientists will get a comprehensive view of the
substorm phenomena from Earth's upper atmosphere to far into space,
pinpointing where and when each substorm begins.

Substorms are atmospheric events visible in the northern hemisphere as
a sudden brightening of the Northern Lights. THEMIS also will provide
clues about the role of substorms in severe space weather and
identify where and when substorms begin.

THEMIS' five identical probes will be the largest number of scientific
satellites NASA has ever launched into orbit aboard a single rocket.
This unique constellation of satellites will line up along the
sun-Earth line, collect coordinated measurements every four days, and
be ready to observe more than 30 substorms during the two-year
mission. Data collected from the five probes will pinpoint where and
when substorms begin, a feat impossible with any previous
single-satellite mission.

"For more than 30 years the source location of these explosive energy
releases has been sought after with great fervor. It is a question
almost as old as space physics itself," said Vassilis Angelopoulos,
THEMIS' principal investigator at the University of California,
Berkeley's Space Sciences Laboratory. "A substorm starts from a
single point in space and progresses past the moon's orbit within
minutes, so a single satellite cannot identify the substorm origin.
The five-satellite constellation of THEMIS will finally identify the
trigger location and the physics involved in substorms."

Researchers have long known that the sudden brightening of the Aurora
Borealis, or Northern Lights, is generated when showers of high-speed
electrons descend along the magnetic field lines to strike Earth's
upper atmosphere. These lights are the visible manifestations of
invisible energy releases, called geomagnetic substorms.

Scientists want to learn when, where, and why solar wind energy stored
within Earth's magnetosphere is explosively released to accelerate
electrons into the Earth's upper atmosphere. To find the answer, the
five THEMIS probes will magnetically map the North American continent
every four days for approximately 15 hours. At the same time, 20
ground stations in Alaska and Canada with automated, all-sky cameras
and magnetometers will document the auroras and space currents from
Earth.

"Many of NASA's future science missions will be constellations of
satellites that will provide simultaneous, three-dimensional views of
nature. THEMIS will give us a deeper understanding of the impact of
the solar wind on the Earth and provide vital data for our manned
explorations as they travel to the moon and beyond," said Frank Snow,
THEMIS project manager at NASA's Goddard Space Flight Center,
Greenbelt, Md.

THEMIS is set to launch in mid-February aboard a Delta II rocket from
Launch Complex 17-B at Cape Canaveral Air Force Station, Fla. For
launch information, news media should contact George Diller, Kennedy
Space Center, Fla., public affairs, at 321-867-2468 or Robert
Sanders, University of California, Berkeley, at 510-643-6998.

THEMIS is the fifth medium-class mission under NASA's Explorer
Program, which provides frequent flight opportunities for world-class
scientific investigations from space within the heliophysics and
astrophysics science areas.

The Explorer Program Office at Goddard manages the NASA-funded THEMIS
mission. The University of California, Berkeley's Space Sciences
Laboratory is responsible for project management, science and
ground-based instruments, mission integration and post launch
operations. Swales Aerospace, Beltsville, Md., built the THEMIS
probes.

For more information about the THEMIS mission and imagery, visit:

www.nasa.gov/themis

-end-

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