Double Star
The mission
The Double Star Project is China's first purely scientific
space mission and its first collaboration with the European Space
Agency. Double Star is designed for magnetospheric research, using
two Chinese spacecraft, TC-1 and TC-2, which each have a payload
consisting of both Chinese and European experiments. The TC-1
spacecraft is in a near-equatorial orbit and TC-2 in a polar orbit. The
launch vehicle was a Chinese Long March 2C . TC-1
launched successfully on 27 December 2003, TC-2 on 25 July 2004. The
Double Star mission was designed with collaboration with ESA's Cluster
mission in mind. The
mission design allows the six spacecraft together to address science
questions that neither Cluster nor Double Star could address alone.
Science objectives
 The
Double Star mission uses two spacecraft flying
in different but carefully chosen orbits to explore the Earth's
magnetosphere. The magnetosphere is a huge region of space surrounding
the Earth where the Earth's magnetic field can be detected. Outside the
magnetosphere is a fast flowing plasma from the Sun, the solar wind.
Inside the magnetosphere we find plasma from the solar wind as well as
the Earth's ionosphere. Furthemore, we know that large amounts of
energy are transferred from the solar wind to the magnetosphere. The
energy is frequently released in dramatic processes, such as substorms,
that generate energetic radiation belt particles, disturb the Earths'
magnetic field at the surface and power the Northern Lights.
Some of the Double Star science goals (e.g. radiation belt
studies) can be addressed with TC-1 and TC-2 alone, but the most
exciting science opportunities arise when Double Star works in
coordination with Cluster. The two Double Star spacecraft plus the
Cluster tetrahedron provide three measurement points separated on a
large scale. The clever part is that these three measurement points
will
be used in ways no previous triad has been used. For example, in late
spring 2004 and 2005, TC-1 will search for solar wind entry points at
the sunward edge of the magnetosphere, while Cluster (and in 2005,
TC-2)
are placed to observe any solar wind plasma that enters and reveal how
it is changed as it travels towards the Earth's atmosphere. In late
summer 2004, Cluster, TC-1 and TC-2 lie at different
distances downstream of the Earth in the magnetotail. Simultaneous
observations in these regions will help us to answer the long-standing
questions of where, when, and how a substorm begins. These remain
unanswered until now because spacecraft have never been properly placed
to make the key observations.
MSSL are Principal Investigator institution for the PEACE
electron spectrometer team, leading an international team of scientific
collaborators. MSSL carried out the work needed to produce two single
sensor electron spectrometers from the two sensor Cluster II Flight
Spare instrument. Additional work was needed to protect the instruments
from the more severe radiation environment that Double Star will
experience, and to render the instruments fully ITAR compliant. It is
planned that a PEACE Operations Team at MSSL will control the
instruments, process their data and carry out in-flight calibration
work.
Further Information
The Double Star homepage at ESA
The Double Star PEACE homepage at MSSL
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