14 Aug 2000

The long-awaited rendezvous of Rumba and Tango with their companions, Salsa and Samba, means that the Cluster quartet is now dancing around the Earth in close formation.

More information.


Paris, 9 August 2000

Lift off for second pair of Cluster II spacecraft

The second pair of Cluster satellites are now safely in separation orbit around the Earth after today’s successful launch from Baikonur Cosmodrome in Kazakhstan.

At 13.13 CEST, (17.13 Baikonur Time - 13.13 CEST) ) a Soyuz-Fregat launch vehicle provided by the French-Russian Starsem consortium lifted off with Cluster satellites FM 5 (Rumba) and FM 8 (Tango).

Approximately 75 minutes into the mission, the Fregat transfer module fired for a second time to insert the spacecraft into a 250 km x 18,000 km separation orbit. About 20 minutes later, the ground station in Kiruna, Sweden, confirmed that the satellites had successfully separated from the Fregat and were now flying in good health.

"This second perfect launch within less than four weeks means that Cluster is on track for a highly successful mission," said Professor Roger-Maurice Bonnet, ESA science director. "We are now looking forward to receiving the unique three-dimensional data that will give new understanding of the interaction between the Sun and Earth."

Over the next week, Rumba and Tango will participate in a complex series of orbital manoeuvres in order to rendezvous with the other spacecraft in the Cluster flotilla (Salsa and Samba).

The quartet will then undergo three months of instrument and system commissioning before beginning their two-year scientific mission. Newsletter for Wednedsay 09 August 2000

Soyuz Rocket Lofts Second Pair of Cluster Probes

  T O D A Y

Space Exploration News From Around the Internet, Updated Every Weekday.
August 9, 2000 - Issue #288


A Soyuz rocket successfully launched the second pair of Cluster II satellites yesterday. The launch occurred right on schedule at 11:13am GMT from the Baikonur cosmodrome in Kazakhstan. The spacecraft will spend the next two days performing a series of maneuvers to bring them into formation with the previously launched pair of satellites. This successful launch is a huge relief for the European Space Agency; these satellites are replacements for a group destroyed in an Ariane 5 mishap four years ago.

Original Source:

ESA Cluster II page

Internet Coverage:

Spaceflight Now
BBC News
Florida Today Space Online

(Full English texts below)

Noordwijk, 9 augustus 2000


In Baikonoer in Kazakstan werd het tweede paar Cluster-satellieten gelanceerd om 13.13 u. Nederlandse tijd. Na de succesvolle lancering van het eerste paar op 16 juli wachtten onderzoekers vol spanning op het zustertweetal. Ook deze lancering vond plaats met een Russische Soyuz-raket van de Russisch-Franse onderneming Starsem.

De Europese ruimtevaartorganisatie ESA heeft voor deze nieuwe satellieten namen gekozen uit 5000 inzendingen van inwoners uit haar lidstaten. De winnende namen, Salsa, Samba, Rumba en Tango zijn bedacht door Rayman Cotton (UK), die werd geinspireerd door de ruimtedans van de satellieten in een langgerekte baan van 19.000 tot 119.000 km boven het aardoppervlak.

Voor het eerst in de geschiedenis van de ruimtevaart vliegen nu vier identieke satellieten in formatie om de aarde. De aandacht van de satellieten is daarbij gericht op het magnetisch veld van onze aarde, dat ons beschermt tegen een constante stroom geladen deeltjes van de zon: de zonnewind. Het Cluster-kwartet geeft ons een beter begrip van het 'weer' in de ruimte. Dit ruimtweer heeft invloed op het leven op aarde. Door 'zonnestormen kunnen elektriciteitscentrales uitvallen, telecommunicatiesatellieten beschadigd raken of satelliet-navigatiesignalen worden gestoord.

NASA Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD

August 7, 2000


The two remaining Cluster spacecraft, set to launch next week, will rendezvous in mid-August with their two sister ships, creating a fleet that will explore a vast but invisible magnetic ocean that surrounds our Earth.

This mysterious region we know as the magnetic field holds off a million mile-per-hour solar wind, and it's where million-amp electric currents surge and ignite a show seen as the northern and southern lights.

Lift-off for the second Cluster duo, named Rumba and Tango, is scheduled for 7:13 a.m. EDT on Wednesday, Aug. 9, aboard a Russian Soyuz rocket from Baikonour, Kazakhstan.

"NASA and the U.S. scientific community are very excited and pleased with the first launch of Cluster spacecraft and eagerly await the second launch," said Larry Christensen, Cluster project manager at NASA's Goddard Space Flight Center, Greenbelt, MD. "This international mission will help us better understand a mysterious region of our space environment that can affect spacecraft and electrical power grids on Earth."

The Earth's magnetic field, called the magnetosphere, is relentlessly blasted and energized by the solar wind, a stream of electrically charged particles that flows constantly from the Sun. During the next two years, as the solar wind buffets Earth's magnetic sea, the Cluster II fleet will penetrate its depths to see how the Earth's magnetosphere responds and interacts with solar wind particles.

By flying in a tetrahedral - or triangular pyramid- formation, the Cluster quartet will study the physical processes that take place between about 11,800 miles (19,000 km) and nearly 74,000 miles (119,000 km) above Earth, providing scientists with the first thorough three-dimensional maps of this shadowy realm.

The first Cluster pair, called Samba and Salsa, launched July 16, reached their parking elliptical orbit on July 21 after a complex series of maneuvers. They await the arrival of the sister spacecraft, Rumba and Tango, to achieve their final observational orbit.

The space quartet will orbit at an apogee of nearly 10,500 miles (16,869 km) and a perigee of more than 75,200 miles (121,098 km) above Earth.

Cluster will join the Solar and Heliospheric Observatory (SOHO) as the second cooperative solar- terrestrial project between NASA and the European Space Agency (ESA). In support of this ESA mission, NASA will provide project management and funding for the U.S. principal investigator and co-investigator hardware investigations, assist ESA managers with launch and early operations support, provide scheduling support, and transmit data from the Wide Band Data experiment on each spacecraft to the University of Iowa via NASA's Deep Space Network.

For a listing of the instruments aboard Cluster, go to:

You also can view a live webcast of the Aug. 9 launch from the ESA website at:


6 Aug 2000

Soyuz/Cluster rollout to launch pad completed

The second pair of Cluster satellites is sitting atop of its Soyuz/Fregat launcher on launch pad #6 at the Baikonur Cosmodrome. Everything is on track for a launch on 9 August 11:13:35 UTC.

Full story


Paris, 31 July 2000

Second Cluster Launch Will Complete the Space Quartet

After the successful launch of the first two Cluster satellites - Salsa and Samba - on 16 July, followed by a perfect insertion into their operational orbits, scientists around the world are eagerly awaiting the launch of the second Cluster pair from Baikonur Cosmodrome in Kazakhstan.

Lift-off for the next duo, FM 5 (Rumba) and FM 8 (Tango), is currently scheduled for 13:13 CEST / 17:13 Baikonur time, on 9 August. Following their release from the Soyuz-Fregat launch vehicle provided by the French-Russian Starsem consortium, the satellites will participate in an almost identical series of complex orbital manoeuvres to their predecessors.

By 15 August, they should have joined their companions to form a unique space quartet. This mini-armada will spend the next two years exploring the interaction between the charged particles swept along in the solar wind and Earth’s magnetic shield – the magnetosphere.

By flying in tetrahedral formation through this magnetic bubble and into interplanetary space, the Cluster quartet will provide the most detailed data yet on the Sun-Earth connection and the physical processes taking place between 19.000 and 119.000 kilometres above our heads.


July 21, 2000

Salsa and Samba in perfect step

After one of the most complex series of manoeuvres ever carried out by Earth-orbiting spacecraft, the first Cluster pair have successfully reached their final elliptical orbit. Salsa and Samba are now dancing in step between 16 869 km (perigee) and 121 098 km (apogee) above the Earth.

Read more.

Estec, ESA

July 17, 2000

First Cluster apogee burn completed

The long, complex process required to elongate the orbits of the first two Cluster spacecraft has begun.

The Cluster mission control centre at the European Space Operations Centre (ESOC) in Darmstadt, Germany, has confirmed that the apogee raising manoeuvre #1 was completed successfully early this afternoon.

Full story.

Lift off from Baikonour Cosmodrome.


July 16, 2000


At 18.39 local time (14.39 CEST) today, the steppes of Kazakhstan reverberated with the roar of rocket engines as a Soyuz-Fregat launch vehicle lifted off from pad 6 at Baikonur Cosmodrome with its precious payload of two Cluster satellites.

Full story.

NEWSALERT: Sunday, July 16, 2000 @ 1020 GMT

The latest news from Astronomy Now and Spaceflight Now


The European Space Agency will make another attempt to launch the first pair of Cluster II satellites today at 1239 GMT (8:39 a.m. EDT). Liftoff was aborted on Saturday when a last-minute problem was detected between the ground system and the Soyuz rocket. We will cover today's launch attempt live.

See our launch preview special report.


July 15, 2000

The launch of the first pair of ESA's Cluster II spacecraft has been postponed due to an anomaly detected between the ground system and the Soyuz launch vehicle. A State Commission, the official body that authorises the launch, was convened to validate the source of the problem and confirmed that both the Cluster II spacecraft and the Soyuz launch, including the Fregat upper stage, are in nominal configuration.

The launch is rescheduled to take place tomorrow, 16 July, at 12:39 GMT (14:39 CEST). The launch will as usual be confirmed by a State Commission which will meet 4 hours before liftoff.

This hold during the launch chronology has demonstrated the robustness of the Soyuz launching process which has been so efficient in the past.

"We are still looking forward to a successful launch tomorrow which will lead to the exciting results that we are expecting from the Cluster mission", said Prof. Roger Bonnet, ESA's Director of Science. This short delay will not have any impact on the spacecraft orbits, the expected science and the launch of the second pair of Clusters still scheduled for 9 August.

Updates on the launch and the live webcast can be followed on the Cluster launch pages.

NASA Headquarters, Washington, DC
Goddard Space Flight Center, Greenbelt, MD

July 13, 2000


An international collaboration will investigate a struggle that's raging in space -- a turbulent battle between the Earth's magnetic field and a solar wind blowing about one to two million miles per hour. Four satellites, flying in formation, will be used to examine this complex interaction between the Earth and the Sun.

It all begins with the first of two launches of the European Space Agency's (ESA) Cluster spacecraft. The first launch is set for July 15 at 8:43 a.m. EDT in Baikonur, Kazakhstan. Two satellites will be carried into orbit by a Russian Soyuz rocket. A second pair is scheduled to launch August 9.

"Cluster is just one example of the marvelous and sophisticated space exploration fleets that can be outfitted through the unselfish cooperation between ESA and NASA," said Larry Christensen, Cluster project manager at NASA's Goddard Space Flight Center, Greenbelt, MD.

During its two-year mission, the quartet of satellites will travel around the Earth in a tetrahedral -- or triangular pyramid -- formation, collecting data where the solar wind, which is a gas comprised primarily of electrons and protons, impacts the Earth's magnetic field. The unprecedented detail provided by Cluster will allow scientists to assemble the first thorough three-dimensional maps of the environment that surrounds and protects our planet.

Each spacecraft will carry the following complement of 11 identical instruments:

  • Active Spacecraft Potential Control (ASPOC) -- will reduce the electric charge on the spacecraft, so very low-speed electrons can be measured. (Austria)
  • Cluster Ion Spectrometry (CIS) -- will measure the relative abundance of protons and helium nuclei and determine their three- dimensional distribution in the solar wind and magnetosphere. (France)
  • Digital Wave Processor (DWP) -- will provide data processing for the plasma wave instruments. (Great Britain)
  • Electron Drift Instrument (EDI) -- will determine strength and direction of the ambient electric field. (Germany)
  • Electric Fields and Waves (EFW) -- will measure fluctuating
  • Fluxgate Magnetometer (FGM) -- will measure static and fluctuating magnetic fields at the spacecraft. (Great Britain)
  • Plasma Electron and Current Experiment (PEACE) -- will provide three-dimensional measurements of electron distributions in the solar wind and magnetosphere. (Great Britain)
  • Research with Adaptive Particle Imaging Detectors (RAPID) -- will measure energetic ions and electrons. (Germany)
  • Spatio-Temporal Analysis of Field Fluctuations (STAFF) -- will measure high frequency waves in the local plasma. (France)
  • Wideband (WBD) Plasma Wave Investigation -- will detect very high-frequency plasma waves at very high time-resolution. (U.S. - - University of Iowa)
  • Waves of High Frequency and Sounder for Probing of Density by Relaxation (WHISPER) -- will use high-frequency plasma waves to probe surrounding plasma to determine the local density of charged particles. (France)

    The current Cluster mission replaces the original spacecraft, which were lost in 1996 shortly after liftoff.

    "Instruments aboard Cluster will provide the only 3-D fast diagnostic tool for studying the Sun-Earth connection and entry of plasma into the magnetosphere," said Dino Machi, Cluster program manager at Goddard. "The mission is extremely important because particularly energetic particles can have a dramatic effect on human activities, disrupting electrical power and telecommunications or causing serious anomalies in satellite operations, especially those in geostationary orbit."

    Cluster will join the Solar and Heliospheric Observatory (SOHO), launched in December 1995, as the second cooperative solar-terrestrial project between ESA and NASA. NASA will provide project management and funding for the U.S. principal investigator and U.S. co-investigator hardware investigations, assist ESA with launch and early operations support, provide scheduling support and transmit WBD data from Cluster to the University of Iowa via the Agency's Deep Space Network.

    More information on this mission can be found on the following Internet web sites: II/Cluster_II.html


    July 12, 2000

    The launch of the first pair of Cluster II spacecraft was given the final go-ahead yesterday in a series of reviews to assess the readiness status of all components.

    Full story.


    10 July 2000


    After years of frustration and hard work following the tragic loss of all four Cluster spacecraft in 1996, UK scientists are eagerly awaiting the launch of the first two Cluster II satellites from Baikonur Cosmodrome in Kazakhstan on 15 July.

    The second pair are currently scheduled to follow on 9 August. Both launches will involve a Soyuz rocket with a newly developed Fregat upper stage.

    Cluster II comprises four identical spacecraft that will fly in a close, tetrahedral (triangular pyramid) formation as they gather information about how the Sun interacts with near-Earth space.

    Following highly elongated, polar orbits which take them between 19,000 and 119,000 km from the planet (almost one third of the way to the Moon) they will investigate most of the major boundaries and regions of interest within the Earth's magnetic environment - the magnetosphere.

    Sometimes, they will be inside this magnetic shield and sometimes they will be outside, fully exposed to the charged particles (mainly electrons and protons) of the solar wind.


    Cluster II is part of an international collaboration to investigate the physical connection between the Sun and Earth.

    Cluster's role is to investigate the interaction between the solar wind - a continuous stream of plasma (electrified gas) that flows from the Sun - and the magnetosphere. It will also investigate what happens during more violent solar events. At such times, near-Earth space is struck by high energy particles from solar flares and plasma clouds that are blasted free during coronal mass ejections (CMEs).

    These sudden eruptions are expected to become more numerous in the summer of 2000 - around the time of the dual Cluster launches - when the Sun will reach the peak in its 11 year cycle of activity.

    Travelling at speeds of 400 km/s or more, CMEs can cross the 150 million km gulf between the Sun and Earth in 2 - 3 days. When they arrive in the Earth's vicinity, the magnetic shield suffers a tremendous buffeting, often resulting in widespread aurorae (the northern and southern lights).

    Particularly severe magnetic storms on the Sun can cause widespread power cuts, damage to TV broadcasting, weather and communication satellites, and disruption to radio communications.


    The four Cluster spacecraft each carry eleven identical instruments to measure the complex interplay of charged particles and electromagnetic fields in near-Earth space.

    As the spacecraft travel through different regions of the magnetosphere, they will provide scientists with their first simultaneous measurements of these phenomena from four nearby locations.

    By comparing and analysing this data, scientists will be able to obtain the first detailed three-dimensional 'map' of near-Earth space and to understand better the physical processes taking place around our planet.

    Early in the mission, the spacecraft will spend most of their time flying through the windsock-shaped magnetic tail, which extends many Moon distances into space on the side of the Earth that faces away from the Sun.

    Six months later, they will investigate the polar cusps, weak points in Earth's magnetic shield where charged particles penetrate the upper atmosphere and generate the aurorae-

    Since plasma is the most common form of matter in the Universe, investigations such as these will be of value for plasma research in terrestrial laboratories. Cluster will also improve our understanding of how space weather results in power cuts, communication breakdowns and damage to satellites used for communication, navigation and weather forecasting.


    U.K. scientists have played a leading role in the development of four out of the 11 science instruments on each Cluster satellite.

  • FGM, the Fluxgate Magnetometer. (Principal Scientific Investigator: Professor André Balogh from Imperial College, London.) Uses two magnetometers to measure magnetic fields along the orbit. These sensors are located along a 5 metre long boom to minimise interference from the spacecraft. The University of Leicester is also involved in FGM.

  • PEACE, the Plasma Electron and Current Experiment. (Principal Scientific Investigator: Dr. Andrew Fazakerley, of Mullard Space Science Laboratory in Surrey.)
    This experiment captures low to medium energy electrons in the space plasma (electrified gas), counts them and measures their direction of travel, speed and temperature. It may also reveal electron beams and plasma waves. Queen Mary & Westfield College, London, and Rutherford Appleton Laboratory (RAL) are also involved in PEACE.

  • DWP, the Digital Wave Processing experiment. (Principal Scientific Investigator: Dr. Hugo Alleyne of Sheffield University.)
    DWP is the control and computing brain for the five instruments that study waves in the surrounding plasma. Its precise timing allows scientists to correlate the studies being made by all four spacecraft. It also has a particle correlator for comparing frequency variations in the electrons around the spacecraft (measured by PEACE) with the wave measurements. Professor Paul Gough of the University of Sussex is responsible for DWP's particle correlator. Queen Mary & Westfield College, London is also involved in DWP.

  • RAPID, the Research with Adaptive Particle Imaging Detectors experiment. (Co-Principal Scientific Investigator: Dr. Manuel Grande of RAL.)
    Scientists at RAL are responsible for the Imaging Electron Spectrometer, one of two instruments on this German-led experiment. This UK contribution will measure electron energies and sort the resulting data.

    Cluster's space-based measurements will be combined with data from the ground-based CUTLASS and EISCAT radars in the Arctic in order to learn more about the complex interactions in the upper atmosphere caused by the solar wind and solar storms. The UK plays a leading role in these ground stations.

    U.K. scientists also run the Cluster Joint Science Operations Centre (JSOC) at RAL. Its main task is to co-ordinate the Cluster science operations, but it will also collect and process the data needed to plan these operations and will monitor the performance of the mission and individual instruments. Dr. Mike Hapgood at RAL is the Project Scientist for JSOC.

    RAL is also home to one of eight Cluster National Data Centres established around the world. These have been set up to process the raw data from a specific set of instruments and then make the information available to the other data centres. Professor Steve Schwartz of Queen Mary & Westfield College, London, is the Project Scientist for the UK Cluster Data Handling Facility, while Dr. Chris Perry is the manager of the Cluster Data Centre at RAL.

    UK industry has also played a leading role in Cluster. Astrium UK (formerly Matra-Marconi Space UK) has provided a number of major subsystems, including attitude and reaction control, and launch support. Logica has provided important software for mission planning and data distribution. Other UK companies have provided components for instruments and spacecraft systems.


    Cluster II and the Solar and Heliospheric Observatory (SOHO) make up the first Cornerstone - the Solar-Terrestrial Science Programme - in the European Space Agency's Horizons 2000 long term science plan.

    Images and data from SOHO have revolutionised our understanding of the Sun since its launch in December 1995. The first Cluster quartet was destroyed in a launch failure during the maiden flight of the Ariane 5 rocket on 4 June 1996. However, its scientific programme was considered so important that the following year ESA and its member states (including the UK) agreed to rebuild the four satellites and their experiments.

    UK funding for the Cluster II instruments has been provided by the Particle Physics and Astronomy Research Council (PPARC).


  • ESA Cluster II site
  • ESA Space Weather site
  • NASA Space Weather site
    UK Web sites:

  • Imperial College, London (Fluxgate Magnetometer)
  • Mullard Space Science Laboratory (Plasma Electron and Current Experiment)
  • Rutherford Appleton Laboratory (Cluster Joint Science Operations Centre)
    The launches will be broadcast live by ESA TV. Further details of the ESA broadcasts are available from:


    July 3, 2000

    Only a few days remain before the start of the European Space Agency's Cluster II mission, a unique expedition to explore the magnetosphere and revolutionise our understanding of the interaction between the Sun and Earth.

    Full story.


    22 Feb 2000

    The European Space Agency (ESA) is launching a public competition to find the most suitable names for its four Cluster II space weather satellites. The quartet, which are currently known as flight models (FM) 5,6, 7 and 8, are scheduled for launch from Baikonur Space Centre in Kazakhstan in June and July 2000.

    Read more about this competition or go directly to the competition webpages

    ESA Science News

    24 Nov 1999

    Cluster Quartet beat the blizzard

    ESA's mission to study space weather has successfully overcome more down-to-Earth weather problems. Despite major transportation difficulties caused by a three-day-long blizzard, all four Cluster II satellites were finally gathered together today for the first and only time in Europe.

    At a special press briefing held to mark the occasion, Professor Roger Bonnet, ESA Science Director, paid tribute to the team that brought the mission back to life after the loss of Cluster I in 1996 and made the event possible.

    "In the past two and a half years, a tremendous amount of work has been completed by both scientists and industry," he said. "It has been a remarkable achievement to build four satellites in such a short time."

    "ESA never rejects science missions because of technical difficulties or other problems, and Cluster II is an example of this determination to succeed," he added. "Three years on, it is still a unique mission. I'm particularly happy that the science of Cluster has not been lost."

    When asked about the practical value of the science data to be returned by Cluster II, Professor Bonnet said, "Solar storms had very little impact on Stone Age people, but the civilisations of the next century will rely heavily on satellites and electronic systems."

    "So we had better have a forecasting system for space weather," he went on. "We need to analyse and observe our nearest star and its effects on the Earth's environment. This is a major justification for ESA's SOHO and Cluster II missions."

    Project manager John Ellwood also praised the efforts of everyone involved in the Cluster II programme.

    "12 hours ago, we thought we would only be able to show you three spacecraft," he said, "The fourth was to have been transported on Monday, but there was a lot of snow, so this was not possible. But thanks to the efforts of Dornier, the spacecraft left Friedrichshafen at 1 am and safely arrived here at 7 am."

    "This is typical of the spirit and endeavour within the Cluster II project," he said.

    Mr. Ellwood then gave the assembled media an update on the status of the four spacecraft, explaining that FM (flight model) 5, is the last of the four spacecraft to be delivered to IABG for environmental testing.

    "The first pair of Cluster II spacecraft have been successfully integrated and completed all of their functional electrical testing," he said. "One is in the thermal-vacuum chamber and will start tests at the end of this week. And the last one has literally just been taken out of its container and will go into its acoustic test programme by the end of this year."

    "Everything is on schedule for the two launches of Cluster II in mid-2000," he concluded. "We are confident that all will be ready by April next year."


  • More about Cluster
  • IABG homepage


    The Cluster quartet at IABG Munich. The leftmost one is FM5, just unpacked. The pair visible on the right hand side have been successfully integrated and completed all of their functional and electrical testing. The satellite visible in the background is in the thermal-vacuum chamber and will start tests within days.

    European Space Agency
    Paris, France

    24 November 1999


    Visitors to the test and integration facilities at IABG near Munich, Germany, on 24 November may be excused for thinking they are suffering from multiple vision. On display there, in a giant clean room, will be not one but four identical cylindrical spacecraft.

    This is the only occasion on which all four of ESA's Cluster II spacecraft will be on display together in Europe.

    Four Spacecraft, One Mission

    The unique event takes place near the end of the lengthy assembly and test programme, during which each individual spacecraft is being assembled in sequence, one after the other.

    Two have already completed their assembly and systems testing and are about to be stored in special containers at IABG prior to shipment to the Baikonur launch site in Kazakhstan next spring. In the case of the other two, flight models 5 and 8, installation of the science payloads has finished, but their exhaustive series of environmental tests at IABG have yet to begin.

    Following delivery to the launch site next April, the satellites will be launched in pairs in June and July 2000. Two Soyuz rockets, each with a newly designed Fregat upper stage, are being provided by the Russian-French Starsem company. This will be the first time ESA satellites have been launched from the former Soviet Union.

    Cluster II is a replacement for the original Cluster mission, which was lost during the maiden launch of Ariane 5 in June 1996. ESA, given the mission's importance in its overall strategy in the area of the Sun-Earth connection, decided to rebuild this unique project.

    ESA member states supported that proposal. On 3 April 1997, the Agency's Science Programme Committee agreed. Cluster II was born.

    European Teamwork

    Scientific institutions and industrial enterprises in almost all the 14 ESA member states and the United States are taking part in the Cluster II project.

    Construction of the eight Cluster / Cluster II spacecraft has been a major undertaking for European industry. Built into each 1200 kg satellite are six propellant tanks, two pressure tanks, eight thrusters, 80 metres of pipework, about 5 km of wiring, 380 connectors and more than 14 000 electrical contacts.

    All the spacecraft were assembled in the giant clean room at the Friedrichshafen plant of prime contractor Dornier Satellitensysteme. On completion, they were sent to IABG in Ottobrunn, near Munich, for intensive vibration, thermal, vacuum and magnetic testing.

    The European ground segment for the mission is just as important. A vast amount of data -- equivalent to 290 million printed pages -- will be returned to Earth over the mission's two-year lifetime. Signals to and from the spacecraft will be sent via a 15 metre antenna at Villafranca in Spain and processed at the European Space Operations Centre (ESOC) at Darmstadt, Germany.

    The main control room at ESOC will be used during the launch and early phases of the mission, with teams of operators working round the clock. About two weeks after the second Cluster II pair are placed in their operational orbits, mission operations will switch to a smaller, dedicated control room at ESOC.

    The Joint Science Operations Centre at Rutherford Appleton Laboratory in the UK will co-ordinate the scientific investigations. Its main task will be to combine all requirements from the 11 science instrument teams into an overall plan.

    The flow of information returned by the 44 instruments will be distributed to eight national data centres, six in Europe, one in the USA and the other in China.

    Solar Maximum

    Cluster II is part of an international programme to find out more about how the Sun influences the Earth. The four Cluster II satellites will join an armada of spacecraft from many countries, which are already studying the Sun and high speed wind of charged particles (mainly electrons and protons) which it continually blasts into space. Ulysses and SOHO, both joint ESA-NASA missions, and ESA's Cluster II , when it will be there, are the flagships of this armada.

    The timing of the mission is ideal, since it will take place during a period of peak activity in the Sun's 11-year cycle, when sunspots and solar radiation reach a maximum.

    Cluster II will measure the effects of this activity on near-Earth space as incoming energetic particles subject the magnetosphere -- the region dominated by the Earth's magnetic field -- to a buffeting.

    Each spacecraft carries an identical set of 11 instruments provided by scientific institutions in different countries.

    Formation Flying

    Cluster II will be the first space science mission ever to fly four identical spacecraft simultaneously. Once the quartet have been inserted into highly elliptical polar orbits, ranging from 19 000 to 119 000 km above the Earth, they will spend the next two years travelling from the magnetosphere into interplanetary space and back again.

    Sometimes they will be within a few hundred kilometres of each other, sometimes 20 000 kilometres apart, depending on the physical phenomena to be studied. By orbiting in a tetrahedral (triangular pyramid) formation, they will be able to make the first detailed three-dimensional study of the changes and processes taking place in near-Earth space.

    As the satellites orbit the Earth, they will investigate the rapid changes which occur in the Earth's magnetosphere when large numbers of electrically charged particles (electrons and protons) in the solar wind reach the Earth. Huge amounts of data will be returned which will help scientists unravel the physical processes and small-scale variations taking place in the near-Earth environment.

    "Cluster II will give us the best information yet on how the Sun affects the near-Earth environment," said Cluster II project scientist, Philippe Escoubet. "For the first time we will be able to study the Earth's magnetic field from four viewpoints with identical instruments."

    "It will be like having four cameras at a football match -- one behind the goal and three others at different angles," he explained. "This is very exciting because it will help us to understand the space environment which surrounds our planet."

    How The Sun Affects Our Planet

    Such studies are not just of academic interest. The Sun affects our world in many ways. Apart from its familiar output of light, heat and ultraviolet radiation, our nearest star also emits a continuous stream of atomic particles -- the solar wind -- that sweeps out into space at speeds ranging from 280 to 1 000 km/s (1 800 times faster than Concorde).

    Sometimes, explosions on the Sun send millions of tonnes of gas towards the Earth. These clouds of high-energy particles can travel the 150 million km between the Sun and Earth in a few days. The most energetic particles of all, created by solar flares, can reach the Earth in just 30 minutes.

    This activity is particularly noticeable at times of solar maximum. When charged particles from the Sun enter the Earth's upper atmosphere, they create shimmering curtains of coloured light, known as auroras, in the polar night sky.

    Other effects can be much more serious:

    For more information, please contact: Further information on Cluster II and the ESA science programme can be found at:

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