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Cluster 2
Cluster 2 -

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Other Designations: Cluster II. Class: Earth. Type: Magnetosphere. Nation: ESA.

The original Cluster mission and the Solar Heliospheric Observatory (SOHO) together comprised the Solar Terrestrial Science Programme (STSP), the first 'Cornerstone' of ESA's Horizons 2000 Programme. These two missions were selected at the same time to investigate the relation between the Sun and the Earth's environment. After its successful launch in December 1995 SOHO provided new information on the effect of the Sun and the solar wind on the Earth's magnetosphere. Following the loss of the original design Cluster spacecraft in June 1996, the approval of the Cluster II mission meant that the STSP objectives could be fulfilled.

The goals of the Cluster II mission were identical to those of the original Cluster and the instrument complement remained the same. Cluster II mission was to conduct an in-situ investigation of the Earth's magnetosphere using four identical spacecraft simultaneously. It was to permit the accurate determination of three-dimensional and time-varying phenomena and make it possible to distinguish between spatial and temporal variations.

Cluster II's main goal was to study the small-scale plasma structures in space and time in the key plasma regions: the solar wind and bow shock; magnetopause; polar cusp; magnetotail; and auroral zone.

The Cluster II spacecraft was basically cylindrical with enormous booms. In the centre was a cylinder with an aluminium honeycomb structure covered with a skin of carbon-fibre reinforced plastic. The equipment panel inside this cylinder supported the main engine, two high-pressure fuel tanks and other parts of the propulsion system.

Six spherical fuel tanks made from titanium were attached to the outside of this central cylinder. Most of the fuel will be consumed soon after launch, during the complex manoeuvres required to reach operational orbit. Each spacecraft also carried eight thrusters for smaller changes of orbit.

Around the central cylinder was the main equipment platform. It consisted of an aluminium-skinned honeycomb panel, which was reinforced by an outer aluminium ring. Most of the subsystems, such as the power and computer processing hardware, were attached to its lower surface, while the science experiments were placed on top. Electrical power was provided by six curved solar panels attached around the outside of the platform. Five silver/cadmium batteries were used for power supply during the four-hour-long eclipses when the spacecraft enter Earth's shadow.

Various rod-shaped booms opened out once the satellite reached orbit. They included two single-hinged antennae for communications and two five-metre, double-hinged booms on the satellite's upper surface which carried sensors which would otherwise be disturbed by the spacecraft. There were also four 50-metre-long wire booms which deployed radially when the spacecraft began to spin. These measured changing electrical fields around each spacecraft.


Design Life: 2 years. Total Length: 1.3 m. Maximum Diameter: 2.9 m. Total Mass: 1,200 kg. Total Payload: 71 kg. Total Propellants: 650 kg. Electric system: 0.22 total average kW. Electrical System: Solar array.

Cluster 2 Chronology

16 July 2000 Samba Launch Site: Baikonur . Launch Vehicle: Soyuz 11A511U / Fregat. Perigee: 16,869 km. Apogee: 121,098 km. Inclination: 90.6 deg.
09 August 2000 Tango Launch Site: Baikonur . Launch Vehicle: Soyuz 11A511U / Fregat. Perigee: 17,200 km. Apogee: 120,600 km. Inclination: 90.0 deg.

Rumba and Tango were the second pair of Cluster II magnetospheric research satellites of the European Space Agency. A series of five burns of the Fregat stage took them from an initial 190 km / 64.8 degree parking orbit to their final 17,200 x 120,600 km orbits inclined 90 degrees to the equator. They then separated from the Fregat and took up operations.

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Last update 12 March 2001.
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© Mark Wade, 2001 .