The European Cluster II space mission, comprising four identical spacecraft, has been launched from Kazakhstan. The spacecraft will fly in close formation around Earth, gathering information about how the Sun affects space weather. The weather in space has a profound impact on the satellites people use everyday for communication, navigation and weather forecasting.
Disaster struck the first attempt to launch this mission in 1996, when the rocket used to launch the spacecraft (the first ever Ariane 5) blew up seconds after take-off - destroying the payload. Since then four new Cluster spacecraft have been built and were launched in two pairs from separate Soyuz rockets.
British scientists – including experts from Leicester - have built and will operate three of the instruments on board each craft. They also have significant involvement in a fourth instrument. Each craft carries eleven instruments, which measure the complex interplay of charged particles and electromagnetic fields that make up the space environment. This information will be sent down to a ground-station on Earth.
The Cluster mission will look particularly at the nature of solar storms that constantly threaten to damage the satellites on which people rely. These storms are also responsible for the displays of ‘aurorae’ or Northern and Southern lights visible close to Earth’s poles.
The Cluster mission is unique in flying four identical spacecraft in formation. Previous missions have only been able to measure conditions at a single point in space. The four Cluster spacecraft will, for the first time, allow scientists to disentangle the differences in space and time within ‘space weather’ fronts and systems.
Lord Sainsbury, Minister for Science, said: ‘The Cluster mission will revolutionise our understanding of the near-Earth space environment. In particular we shall gain important knowledge on the dynamics of space climate and its impact on global satellite systems. This will enable us to ‘harden’ spacecraft against solar storms and thus protect world-wide communication channels - a clear example of science delivering real commercial benefits.’ The Minister added, ‘Cluster is a truly innovative European spacecraft mission and a triumph for British scientists who first dreamt up the mission and for UK industry who have played such a vital and integral role in its design and construction.’
Professor Stanley Cowley, Head of the Radio & Space Plasma Group at the University, said: “I was first involved in Cluster in the early 1980s, when I served as a member of an ESA study team to study the feasibility of the mission. We recommended to ESA that it was feasible and should be done.
“Later, the Group of which I was then head at Imperial College (London) won an international competition to build the magnetic field experiment on the spacecraft, and I became a co-investigator on this experiment, with consequent rights to work with the data. I moved to Leicester in 1996 to become head of the Radio & Space Plasma Physics Group, and will play a full role in the Cluster analysis from here.
“The particular forte of our Group is to build radio and radar systems to probe the Earth’s upper atmosphere and ionosphere. At present we operate the CUTLASS pair of radars located in Iceland and Finland, which measure the flow over the north polar regions.
“During the Cluster mission we will be conducting a series of novel experiments between Cluster and CUTLASS timed for periods when the field-of-view of the radars and the spacecraft are joined together by the Earth’s polar magnetic field line, though separated physically by tens of thousands of km. We will look for corresponding dynamic phenomena in the spacecraft and radar data, communicated from one to the other along the Earth’s field.
“We are also building a new high-power radar called SPEAR, which we plan to deploy on Svalbard and start operating in 2003. This system will undertake new active experiments with Cluster towards the end of the mission.
“While our group goals in working with Cluster are to understand the tricky physics which governs the Earth’s outer environment, and how it interacts both with the outer atmosphere of the sun (the solar wind which blows continuously out into the solar system at ~500 km s-1), and with the Earth’s underlying ionosphere and atmosphere, there are also good practical reasons for work in this area.
“First, this is the environment (a hostile one) in which a range of applications satellites have to operate - e.g. communications (TV, phone), meteorology (weather forecasting), navigation (GPS), military (communications and surveillance). These now represent huge industries, and the active elements (the spacecraft) have to be designed to operate safely in it.
“Second, a wide range of terrestrial systems are also effected - e.g. radio communication links, over-the-horizon radars, and power lines. The space environment is not only hostile, it is also highly variable, due to the strongly variable gas and magnetic field output of the sun. It is one of the tasks of Cluster to study the response of the Earth’s outer environment to these variations.”
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