NASA THEMIS mission adds five spacecraft to the Sun-Earth flotilla(Forwarded)

ESA News
http://www.esa.int

16 February 2007

NASA THEMIS mission adds five spacecraft to the Sun-Earth flotilla

Tonight NASA plans to launch its five THEMIS scientific satellites onboard
a Delta-2 rocket from Cape Canaveral, Florida USA, to join the spacefleet
of Sun-Earth connection explorers -- four from the ESA Cluster mission and
two from the CNSA/ESA Double Star mission.

The main scientific objective of THEMIS (Time History of Events and
Macroscale Interactions during Substorms) is to find what triggers
magnetic substorms. This phenomenon corresponds to periods of time during
which violent changes happen within the Earth's magnetic environment or
magnetosphere. It is triggered at distances from one tenth to half the
Earth-Moon distance on the nightside of Earth and hurls energetic
particles towards our planet. These particles are responsible for the very
bright and colourful auroras and are usually harmless. However, when the
Sun unleashes massive clouds of charged particles towards Earth, a series
of 10 or more substorms can occur in rapid succession. Such a series may
be responsible for the failure of power grids and satellites observed
during some of these events.

Six plus five equals eleven

Cluster is the first space mission composed of four satellites flying in
formation to study the Sun-Earth connection. Launched in 2000, this
mission, originally planned for two years, has been extended to the end of
2009. It was joined in 2003 by the first Double Star spacecraft named TC-1
and in 2004 by TC-2, both partially equipped with spare instruments of the
Cluster satellites. Double Star is the first Chinese scientific space
mission in the Earth's magnetosphere.

The THEMIS satellites will be highly complementary to the Cluster and
Double Star ones since they will monitor opposite regions of the
magnetosphere with respect to Earth. For example, during winter season
2007/2008, while THEMIS will be in the magnetotail (nightside) studying
the source region of the substorms, the Cluster mission will spend a
significant part of its orbit around Earth in the solar wind (dayside) and
cross the auroral region at mid-altitude. The apogee of TC-1 is located
approximately in between. For the first time, about half of the
magnetosphere and its environment will be monitored simultaneously by
state-of the-art scientific instrumentation, thanks to these three
missions.

European involvement

THEMIS is the fifth medium*class mission selected by NASA under its
Explorer Program with Professor Vassilis Angelopoulos (Space Science
Laboratory of UC Berkeley, USA) as Principal Investigator of the mission.
Each THEMIS satellite carries an identical set of five scientific
instruments. The development of two of these instruments was done in close
collaboration between American and European institutes from Austria,
France and Germany. Part of the electronics of these instruments has been
manufactured in Europe. Several European research institutes will take an
active part in the scientific exploitation of these future measurements.
Such a deep scientific collaboration is not a first. It is built on years
of fruitful collaboration such as that on Cluster where discoveries have
been made thanks to active collaboration between researchers from both
sides of the Atlantic.

"This is the first time in history of Space Physics that such a high
number of scientific satellites are in operation simultaneously. It
represents an unprecedented opportunity to study the global
solar-magnetospheric environment and the physical processes involved. We
wish all the best to our American colleagues for a successful launch",
says ESA's Philippe Escoubet, Double Star and Cluster project scientist.

For more information on the Sun-Earth explorers, contact:

Philippe Escoubet
ESA Cluster Project Scientist
Email: philippe.escoubet @ esa.int

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