Cluster96

Description

The original Cluster program of four spacecraft (all launched together on the same rocket) experienced a launch failure in 1996. Following that, a single replacement Cluster spacecraft was authorized in July of 1996, and in April 1997 a further three near-replicas of the original spacecraft were also approved, thus completing the replication of the original four-spacecraft Cluster mission. The following text describes one of the original identical four Cluster spacecraft destroyed at launch. The spacecraft of the new replacement mission, Cluster II, are described elsewhere, under the NSSDC IDs 2000-041A, 2000-041B, 2000-045A, and 2000-045B, and the names Cluster 2/FM5 (Rumba), Cluster 2/FM6 (Salsa), Cluster 2/FM7 (Samba), and Cluster 2/FM8 (Tango).

Cluster-A, one of the four similar spacecraft of the Cluster mission, is part of ESA's and NASA's Solar-Terrestrial Science Program (STSP). The purpose of the mission is to study small-scale structures in three dimensions in the Earth's plasma environment, such as those involved in the interaction between the solar wind and the magnetospheric plasma, in global magnetotail dynamics, in cross-tail currents, and in the formation and dynamics of the neutral line and of plasmoids. The four spacecraft will orbit in a tetrahedral formation in 4 x 22 Re, near-polar orbits with relative separations of several hundred kilometers at periapsis. The tetrahedral formation is essential for making three-dimensional measurements and for determining the curl of vectorial quantities such as the magnetic field.

Each spacecraft will be spin-stabilized and cylindrical in shape, with a 2.9 m diameter and 0.9 m length. It will have two rigid 5 m magnetometer booms and two pairs of wire booms, with 100 m tip-to-tip lengths, for electric field measurements. Each spacecraft will have AC and DC magnetometers, an electric fields and waves sensor, an electron emitter/detector, an electron density sounder, electron and ion plasma analysers, an energetic particle detector, an ion emitter, and a data processing unit.

Cluster operations will be performed by ESA with support from NASA's Deep Space Network. Cluster is also an IACG mission. A more detailed description of the spacecraft and experiments may be found in ``Cluster: Mission, payload and supporting activities,'' ESA SP-1159, March 1993.