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The BBC's Tom Heap
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Sunday, 16 July, 2000, 18:17 GMT 19:17 UK
Cluster satellites go into orbit
The Soyuz rocket is successfully launched - at last
The Soyuz rocket is successfully launched - at last
A European mission to study the physics of so-called space weather has blasted off from Baikonur in Kazakhstan.

Two satellites of the Cluster II programme were sent into orbit onboard a Russian Soyuz-Fregat rocket.

They went up a day late after a technical problem at the space port.

Cluster II is a "recovery" mission. The first attempt was destroyed at launch when the Ariane-5 heavy-lift rocket blew up 40 seconds into its maiden flight in 1996.

The programme actually comprises four identical satellites that will fly in a close, tetrahedral (triangular pyramid) formation - a first for a group of spacecraft.

The two satellites launched on Sunday will be followed by another pair on 9 August.

Magnetic shield

The Cluster quartet will investigate most of the major boundaries and regions of interest within the Earth's magnetic environment - the magnetosphere.

Cluster facts
Spin rate: 15 rpm
Spacecraft diameter: 2.9 m
Spacecraft height: 1.3 m
Dry mass: 550 kg
Propellant mass: 650 kg
Solar array power: 224 W
Downlink rate: 2 to 262 kbit/s
The magnetosphere protects life on Earth from the stream of charged solar particles - electrons and protons - that are blasted continuously from the Sun.

Cluster's role will be to look at how the magnetosphere interacts with this solar wind, and the high-energy particles from more violent solar events such as flares and so-called coronal mass ejections (CMEs).

There is currently a great deal of interest in these space weather phenomena. The charged particles, which move at hundreds of kilometres a second, can knock out electronics onboard satellites and in extreme cases interfere with power grids on the Earth's surface.

Weak points

Armed with data from Cluster II, scientists hope that they will be able to predict such threats to satellites with more certainty.

Cluster Esa
Scientists have spent four years rebuilding the Cluster programme
Early in the mission, the spacecraft will spend most of their time flying on the side of the Earth that faces away from the Sun.

After six months, they will move in front of the planet to investigate the polar cusps.

These are weak points in the Earth's magnetic shield, where charged particles penetrate the upper atmosphere and generate the spectacular Northern and Southern Lights.

From the end of December, data will be coming down from the four satellites at a rate of one gigabyte (two compact disks) every day.

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See also:

04 Jul 00 | Sci/Tech
Cluster mission launch bumped
20 Feb 00 | Washington 2000
'And here's today's space weather forecast...'
19 Feb 00 | Washington 2000
National grid gets space protection
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