Press Release

Success for Early Double Star Launch

By SpaceRef Editor
July 26, 2004
Filed under , ,
Success for Early Double Star Launch

A rare event in the history of space exploration took place yesterday
(25 July) when the second European-Chinese Double Star spacecraft
lifted off a day early from Taiyuan spaceport, west of Beijing, on a
Long March 2C rocket.

The launch of the spacecraft, officially called Tan Ce 2 (Explorer 2), was
brought forward one day to avoid bad weather. Lift off occurred at 08:05:18
BST (07:05:18 GMT or 15.05:18 local time).

Preliminary analysis of spacecraft data indicate that the spacecraft has
been successfully inserted into a polar orbit ranging from 681 km to 38,278
km above the Earth, and that its experiment booms have deployed correctly.

Tan Ce 2 is the second spacecraft to be built for the Double Star programme,
a unique collaboration between Chinese and European scientists. Its
predecessor, Tan Ce 1 (Explorer 1), was successfully launched on a similar
rocket from a launch site in Xichang on 29 December 2003 and is now
returning a rich stream of data.

Eagerly awaited by UK scientists, who have played a major role in the
Double Star missions, Tan Ce 2 will complete a six spacecraft
Sino-European constellation designed to solve a 30 year-old space
mystery: what happens when magnetic storms are generated above
the Earth?

“We are delighted that everything seems to be going according to
plan,” said Andrew Fazakerley (MSSL-ICL), one of the UK principal
investigators for both Double Star and Cluster.

UK teams play major roles in both Double Star and Cluster, through
provision of instruments and involvement in science operations.

Seven of the eight European instruments on the pair of Double Star
spacecraft (including five led by the UK) are copies of instruments
on Cluster.

The Plasma Electron and Current Experiment (PEACE) on TC-1 and
TC-2 was provided by the Cluster team at Mullard Space Science
Laboratory, led by Andrew Fazakerley. This measures the speed,
direction and population of electrons around the spacecraft.

Principal Investigator for the Fluxgate Magnetometer (FGM)
experiments on TC-1 and lead Co-Investigator for the TC-2 FGM is
Chris Carr from the Cluster team at Imperial College London.
These instruments can measure a magnetic field in space 1,000
times weaker than the field at the Earth’s surface.

An experiment on TC-1 that measures waves (rapid variations in the
magnetic field) includes the Digital Wave Processor (DWP)
instrument, developed by the Cluster team at the University of
Sheffield, under the leadership of Hugo Alleyne.

In addition, Double Star will draw on science operations expertise
at the Rutherford Appleton Laboratory (RAL). RAL has been
running the Cluster Joint Science Operations Centre (JSOC) since
the beginning of 2001 and has adapted this to provide a similar
service for Double Star. This European Payload Operations Service
(EPOS) works with the European instrument teams on Double Star
to co-ordinate the commanding of their instruments and delivers the
finalised commanding to the Double Star Science Application
System in Beijing.

RAL is also providing the Double Star Data Management System
that will exchange key data products generated by the instrument
teams between national data centres in Austria, France and the
UK, and enable scientists and the general public to browse and
retrieve those products.

Mike Hapgood, lead scientist for both the Cluster JSOC and Double
Star EPOS, says, “This is a great opportunity to advance our
understanding of the large-scale behaviour of the Earth’s


Double Star is the first major collaboration between Europe and
China on a scientific space mission. A major challenge has been
to compare the methods used to develop space missions in Europe
and China and to develop efficient ways of working together.

Each Double Star spacecraft is a spinning cylinder about 2 metres
across and 1 metre high.

Tan Ce 1 (TC-1) is flying in a highly elliptical equatorial orbit of 570 x
78,850 km altitude (354 x 48,997 miles), inclined at 28.5 degrees to
the equator. Over a lifetime of at least 18 months, it will sample key
regions on the day and night sides of the Earth where the process of
magnetic reconnection occurs. These reconnection processes
dominate the dynamics of the magnetosphere.

The 343 kg drum-shaped Tan Ce 2 (TC-2) will observe the Earth’s
changing magnetosphere from a highly elliptical polar orbit.
Over a period of at least one year, it will sample the polar cap
and cusps – the main regions where energy from the Sun flows
into the magnetosphere. Those energy flows are largely controlled
by the reconnection processes to be studied by TC-1.

European institutes contribute eight of the 16 Double Star scientific
instruments and part of the network of data systems on the ground.
These instruments are almost identical to some of those that have
been flying on the Cluster quartet since the summer of 2000.

The four identical Cluster spacecraft — Rumba, Salsa, Samba and
Tango — pirouette around the Earth in close formation, carrying out
unique multi-scale, 3-D observations of the electrically charged
particles in the solar wind and their battle with the magnetosphere.

In order to allow the combined observations by six spacecraft, the
lifetime of ESA’s Cluster mission has been extended three years
until the end of 2005. If all goes well, the lifetime of all the
spacecraft may be further extended to increase the scientific
return of this unique constellation.

The turbulent interaction between the supersonic solar wind and
Earth’s protective magnetic shield is revealed in various ways. The
arrival of huge clouds of magnetised particles (known as coronal
mass ejections) at the Earth gives rise to the beautiful aurorae
— the Northern and Southern Lights — but it can also produce
magnetic storms that may have serious consequences for human
activities, from power cuts to damaged satellites and communication

SpaceRef staff editor.