East meets West to solve space storm mystery (Forwarded)

Royal Astronomical Society Press Notice

Issued by Peter Bond, RAS Press Officer
PeterRBond -at- aol.com, tel: +44 (0)1483-268672

Contact details for this release are listed at the end.

************************************************** ************

Date: 19th July 2004

PN04-27

EAST MEETS WEST TO SOLVE SPACE STORM MYSTERY

The exploration of near-Earth space will enter a new phase on 26 July when a
spacecraft called Tan Ce 2 (Explorer 2) lifts off from Taiyuan spaceport, west
of Beijing, on a Chinese Long March 2C rocket. The launch is currently scheduled
to take place at 08:23 BST (07:23 GMT).

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?

MYSTERIOUS STORMS AND EARTH'S MAGNETIC SHIELD

Double Star is the first Chinese programme dedicated to space science, and the
first international space mission involving China. It has been designed to
operate alongside the European Space Agency's groundbreaking Cluster mission, in
which a mini-flotilla of spacecraft flies in formation around the Earth.

This joint enterprise involving East and West will revolutionise our knowledge
of the Earth's magnetosphere -- the huge, tadpole-shaped region of space
dominated by our planet's magnetic field -- and its struggle to protect our
planet from the supersonic particles that stream towards us from the Sun.

The four Cluster spacecraft have been orbiting together since 2000, flying over
Earth's magnetic poles and revealing for the first time processes which were
only hinted at by earlier missions involving single spacecraft. Together with
Cluster, the two Tan Ce spacecraft will be used to study the link between the
solar wind and geomagnetic activity, and to provide the most detailed,
multi-dimensional view of the complex magnetosphere ever obtained.

The most exciting investigation is the search for the cause of explosive
magnetospheric substorms, which has been eluding space scientists since their
discovery, more than 30 years ago. These storms can cause havoc with compasses
and power systems on the ground.

During August and September, the four Cluster spacecraft will be spending much
of their time travelling on the nightside of the Earth, in a region known as the
magnetotail. Careful orbit design has arranged that the two Double Star
spacecraft will periodically join them in this region. Flying closer to the
Earth, they will complete the chain of six spacecraft located at different
distances from our planet.

Scientists hope that this arrangement will enable them to tie down the location
of the onset of a substorm, when large amounts of energy are explosively
released from the Earth's magnetic field by a process known as magnetic
reconnection. This energy accelerates charged particles in the magnetotail and
drives powerful electrical currents down into the ionosphere, a region of the
upper atmosphere. The most obvious manifestations of these particle streams are
spectacular auroral displays and disruptions to the magnetic field.

As yet, no one knows exactly where the energy release process begins, so it is
not possible to choose between several theories of the origin of these
substorms. Mission scientists hope that accurate measurements by the
Cluster/Double Star sextet will answer this problem, and in doing so beat a
dedicated five spacecraft mission being developed by NASA (named THEMIS, due for
launch in autumn 2006) to solving the mystery!

"On its own, Double Star is scientifically important because it provides new
measurements in key regions of magnetosphere," said Andrew Fazakerley
(MSSL-UCL), one of the Principal Scientific Investigators (PIs) from the UK.
"For example, it will provide important new information on the Earth's
ever-changing radiation belts."

"However, the really exciting part is that the orbits of the two spacecraft are
explicitly designed for co-ordinated measurements with Cluster," he added. "So,
when Cluster is in the distant magnetic tail and Double Star is in the near
tail, we shall be able to see simultaneously for the first time what happens in
both of these key regions when the huge amounts of energy that drive the
substorms are released."

UK EXPERIMENTS

UK teams play major roles in both Double Star and Cluster, both 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 magnetosphere."

NOTES FOR EDITORS

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.

Tan Ce 2 (TC-2) will fly in a highly elliptical polar orbit of 700 x 39,000 km
(440 x 24,375 miles). Over a period of at least one year, it will sample the
polar cap and cusp regions. These are 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 breakdowns.

CONTACTS:

Chris Carr
PI for the Fluxgate Magnetometer [FGM] (TC-1)
Space and Atmospheric Physics Group
Imperial College
London, SW7 2BZ
Tel: +44 (0)20-7594-7765
Mobile: +44 (0)7714-713377
E-mail:

Dr. Andrew Fazakerley
PI for the Plasma Electron and Current Experiment [PEACE] (TC-1 and TC-2)
Mullard Space Science Laboratory / University College London
Holmbury St. Mary
Dorking
Surrey, RH5 6NT
Tel.: +44 (0)1483-204175
Mobile: +44 (0)7712-760269
E-mail:

Dr. Christopher J. Owen
Co-I for PEACE (see above)
Mullard Space Science Laboratory / University College London
Tel.: +44 (0)1483-204281
Mobile: +44 (0)7793-671072
E-mail:

Dr. Hugo Alleyne
PI for the Digital Wave Processor [DWP] (TC-1)
Space Systems Group
Department of Automatic Control & Systems Engineering
University of Sheffield
Mappin Street
Sheffield, S1 3JD
Tel: +44 (0)114-222-5630
Fax: +44 (0)114-222-5661
Email:

Dr. Mike Hapgood
Lead Scientist, Satellite Operations Group
Rutherford Appleton Laboratory
Chilton
Didcot
OXON, OX11 0QX
Tel.: +44 (0)1235-446520
Mobile: +44 (0)789-9908780.
E-mail: or

Trevor Dimbylow
Manager, RAL science operations projects
Rutherford Appleton Laboratory (see above)
Tel.: +44 (0)1235-445827
E-mail:

FURTHER INFORMATION CAN BE FOUND AT:

* Double Star (ESA)
http://sci.esa.int/doublestar
* Cluster (ESA)
http://sci.esa.int/cluster
* Chinese National Space Administration
http://www.cnsa.gov.cn/main_e.asp
* DWP home page
https://www.shef.ac.uk/space-systems...r_mission.html
* FGM home page
http://www.imperial.ac.uk/research/s...star/index.htm
http://www.iwf.oeaw.ac.at/english/welcome1024_e.html
* PEACE homepage
http://www.mssl.ucl.ac.uk/www_plasma...s/double_star/
* Double Star data and orbit visualisations
http://edds02.iwf.oeaw.ac.at/dsdsweb/
* Rutherford Appleton Laboratory (Cluster / Joint Science Operations Centre)
http://jsoc1.bnsc.rl.ac.uk/pub/DSP_c...eStar_RAL.html

In message , Andrew Yee
writes
Royal Astronomical Society Press Notice

Issued by Peter Bond, RAS Press Officer
PeterRBond -at- aol.com, tel: +44 (0)1483-268672

Contact details for this release are listed at the end.

************************************************* *************

Date: 19th July 2004

PN04-27

EAST MEETS WEST TO SOLVE SPACE STORM MYSTERY

Tan Ce 2 (TC-2) will fly in a highly elliptical polar orbit of 700 x
39,000 km (440 x 24,375 miles). Over a period of at least one year, it
will sample the polar cap and cusp regions.

Possibly a dumb question, but does that mean the apogee is over one of
the poles?

Jonathan Silverlight wrote:

In message , Andrew Yee
writes
Royal Astronomical Society Press Notice

Issued by Peter Bond, RAS Press Officer
PeterRBond -at- aol.com, tel: +44 (0)1483-268672

Contact details for this release are listed at the end.

************************************************* *************

Date: 19th July 2004

PN04-27

EAST MEETS WEST TO SOLVE SPACE STORM MYSTERY

Tan Ce 2 (TC-2) will fly in a highly elliptical polar orbit of 700 x
39,000 km (440 x 24,375 miles). Over a period of at least one year, it
will sample the polar cap and cusp regions.

Possibly a dumb question, but does that mean the apogee is over one of
the poles?

I don't know the initial orientation of the orbit, but the earth's
oblateness will induce apsidal motion at the rate

d(omega)/dt = (3 J_2 r_e^2 n) (5 cos^2 i - 1) / (4 a^2 (1-e^2)^2).

We have r_e = 6378.14 km and J_2 = 1.08263E-3. The perigee and apogee
are 7078 and 45378 km respectively; this means that a = 26228 km and
e = 0.7301. Now the Earth's GM is 398600.48 km^3/sec^2 = a^3 n^2, so
n = 1.4864E-4 rad/sec. We aren't given the inclination, so I'll assume
it's 90 degrees for a perfectly polar orbit. (I shouldn't be surprised
if it's slightly retrograde, producing a "sun-synchronous" orbit in
which
the node progresses at the rate of 1 revolution per year.) All that's
left is to plug in the numbers:

d(omega)/dt = (19.639) (-1) / (5.9985E+8) rad/sec
= -3.274E-8 rad/sec
= -0.162 deg/day

so that the perigee will move from the north pole to the south pole in
a little more than 3 years. Most probably they'll want to launch it
with
an argument of perigee a bit more than 90 (or 270) degrees, so that the
perigee will sweep over the north (or south) pole during the first year
in orbit. And of course the apogee will be over the other pole.

-- Bill Owen

In message , Bill Owen
writes
Jonathan Silverlight wrote:

In message , Andrew Yee
writes
Royal Astronomical Society Press Notice

Issued by Peter Bond, RAS Press Officer
PeterRBond -at- aol.com, tel: +44 (0)1483-268672

Contact details for this release are listed at the end.

************************************************* *************

Date: 19th July 2004

PN04-27

EAST MEETS WEST TO SOLVE SPACE STORM MYSTERY

Tan Ce 2 (TC-2) will fly in a highly elliptical polar orbit of 700 x
39,000 km (440 x 24,375 miles). Over a period of at least one year, it
will sample the polar cap and cusp regions.

Possibly a dumb question, but does that mean the apogee is over one of
the poles?

I don't know the initial orientation of the orbit, but the earth's
oblateness will induce apsidal motion at the rate

d(omega)/dt = (3 J_2 r_e^2 n) (5 cos^2 i - 1) / (4 a^2 (1-e^2)^2).

We have r_e = 6378.14 km and J_2 = 1.08263E-3. The perigee and apogee
are 7078 and 45378 km respectively; this means that a = 26228 km and
e = 0.7301. Now the Earth's GM is 398600.48 km^3/sec^2 = a^3 n^2, so
n = 1.4864E-4 rad/sec. We aren't given the inclination, so I'll assume
it's 90 degrees for a perfectly polar orbit. (I shouldn't be surprised
if it's slightly retrograde, producing a "sun-synchronous" orbit in
which
the node progresses at the rate of 1 revolution per year.) All that's
left is to plug in the numbers:

d(omega)/dt = (19.639) (-1) / (5.9985E+8) rad/sec
= -3.274E-8 rad/sec
= -0.162 deg/day

so that the perigee will move from the north pole to the south pole in
a little more than 3 years. Most probably they'll want to launch it
with
an argument of perigee a bit more than 90 (or 270) degrees, so that the
perigee will sweep over the north (or south) pole during the first year
in orbit. And of course the apogee will be over the other pole.

Thanks. I've found that the Heavens Above site lists it
(http://www.heavens-above.com/ - look for Double Star or the US Space
Command ID 28382) and quotes a 666 x 38,566 km orbit inclined at 90.0°.