This Cluster II spacecraft, FM5 (Rumba), is also known as Phoenix, after a mythical Arabian bird which was
burnt on a funeral pile and then rose from the ashes to live again. The original Cluster of four spacecraft experienced
a launch failure in 1996. (NSSDC will carry the name "Cluster96" in its information files to designate the unsuccessful
1996 four-spacecraft Ariane 5 launch.)

Phoenix was approved in July 1996 as a replacement for the lost four-spacecraft group. It was later (April 1997) agreed that
the potential science return from a full Cluster reflight was so important that a further three near-replicas of the original
spacecraft would also be built.

This Cluster II spacecraft, FM5 (Rumba), was launched together with FM8 (Tango) by a Soyuz-Fregat rocket from Baikonur. The
four similar spacecraft of the Cluster II mission are part of ESA's and NASA's Solar-Terrestrial Science Program (STSP). The
purpose of the Cluster II 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 Cluster II spacecraft will orbit in a tetrahedral formation in near-polar orbits of nominally 4 x 19.6 Earth radii,
with period about 57 hours, and inclination about 90.7 degrees. Relative distances between the spacecraft will be adjusted
in the course of the mission, depending on the spatial scales of the structures to be studied, varying from a few hundred
km to a few Earth radii. The tetrahedral formation is essential for making three-dimensional measurements and for determining
the curl of vectorial quantities such as the magnetic field.

The orbits of all four spacecraft will be frequently maneuvered so as to achieve the targeted investigations.

Each spacecraft will be spin-stabilized, normally at around 15 rpm, and will be cylindrical in shape, with a
2.9-m diameter and 1.3-m length. It will have two rigid 5-m radial experiment booms, four 50-m experiment wire booms,
and two axial telecommunications antenna booms. Telemetry downlink bit rate will be 2 to 262 kbit/s.

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 ESOC in Darmstadt, Germany, with support from NASA's Deep Space Network.
Cluster is also an IACG mission. The scientific data are distributed by ESOC using CD-ROM as a medium to the
Principal Investigators, Co-Investigators and the network of eight national data centres (6 in Europe, 1 in USA
and 1 in China) that form the Cluster Science Data System (CSDS). There are approximately 80 recipients world-wide.
Science operations are carried out by the Joint Science Operations Centre, co-located with the UK data centre at RAL,
Didcot. A wide scientific community will have differing rights of access to the Cluster data. Scientists wishing
to access Cluster data should contact their national Data Centres.

ESA SP-1159, Paris, March 1993 is entitled "Cluster: Mission, Payload and Supporting Activities" Edited by W. R. Burke.
European Space Agency, ESA SP-1159, 1993.ISBN: 92-9092-073-4.