Cluster 2

The original Cluster mission and the Solar Heliospheric Observatory (SOHO) together comprised the Solar Terrestrial Science Program (STSP), the first 'Cornerstone' of ESA's Horizons 2000 Program. 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 aluminum honeycomb structure covered with a skin of carbon-fiber 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 would be consumed soon after launch, during the complex maneuvers 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 aluminum-skinned honeycomb panel, which was reinforced by an outer aluminum 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-meter, 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. Typical orbit: 17034 x 120849 km, 90.2 deg inclinaton. Length: 1.30 m (4.20 ft). Maximum Diameter: 2.90 m (9.50 ft). Mass: 1,200 kg (2,600 lb). Payload: 71 kg (156 lb). Main Engine Propellants: 650 kg (1,430 lb). Electrical System: Solar array. Electric System: 0.22 average kW.

• 2000 July 16 - Samba - Launch Site: Baikonur. Launch Complex: LC31. Launch Vehicle: Soyuz. Mass: 1,200 kg (2,600 lb). Perigee: 21,449 km (13,327 mi). Apogee: 116,279 km (72,252 mi). Inclination: 88.50 deg. Period: 3,423.40 min.
  The first two European Space Agency Cluster II satellites, Samba (FM7) and Salsa (FM6) were launched into an initial 200 km / 64.8 deg circular orbit. The Fregat upper stage then burned once before ejecting the satellites into a 250 x 18072 km x 64.7 deg transfer orbit. Both satellites then used their Astrium (former MBB) S400 liquid engines in a series of four additional burns before reaching their final 16869 x 121098 km x 90.6 deg orbits. Each magnetosphere research satellite deployed four 50-meter wire antennas.

• 2000 July 16 - Salsa - Launch Site: Baikonur. Launch Complex: LC31. Launch Vehicle: Soyuz. Mass: 1,200 kg (2,600 lb). Perigee: 21,430 km (13,310 mi). Apogee: 116,294 km (72,261 mi). Inclination: 88.60 deg. Period: 3,423.20 min.
  

• 2000 August 9 - Tango - Launch Site: Baikonur. Launch Complex: LC31. Launch Vehicle: Soyuz. Mass: 1,200 kg (2,600 lb). Perigee: 21,430 km (13,310 mi). Apogee: 116,300 km (72,200 mi). Inclination: 88.50 deg. Period: 3,423.40 min.
  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.

• 2000 August 9 - Rumba - Launch Site: Baikonur. Launch Complex: LC31. Launch Vehicle: Soyuz. Mass: 1,200 kg (2,600 lb). Perigee: 21,430 km (13,310 mi). Apogee: 116,297 km (72,263 mi). Inclination: 88.50 deg. Period: 3,423.30 min.