Cluster II operations

The Cluster II constellation: four identical satellites orbiting in formation. Cluster is operated from ESA's ESOC mission control centre, and science operations are managed from the JSOC
Cluster II

The Cluster II mission comprises four spacecraft, named Samba, Tango, Rumba and Salsa, orbiting Earth in a tetrahedral configuration. 

The four spacecraft are collecting the most detailed data yet on small-scale changes in near-Earth space, and the interaction between the charged particles of the solar wind and Earth's atmosphere. These enable scientists to build a three-dimensional model of the magnetosphere and to better understand the processes taking place inside it. 

Each of the four spacecraft carries an identical set of 11 instruments to investigate charged particles, electrical and magnetic fields. These were built by European and American instrument teams. 

ROLEIn-situ investigation of Earth's magnetosphere
LAUNCH DATES16 July & 9 August 2000
LAUNCHER/LOCATIONSoyuz-Fregat (2 x dual launches)
Baikonur, Kazakhstan
LAUNCH MASS1200 kg (each)
ORBITHighly elliptical; between 6 and 20 000 km apart
NOMINAL MISSIONTwo years; extended currently to 2016
+ Studying the Solar Wind and the relationship between the Sun and Earth's magnetic environment +
 

The mission

Cluster was first proposed in November 1982 and was ready for launch in 1996. Unfortunately the first four Cluster spacecraft were lost during the Ariane-501 lift-off from Kourou, French Guiana, on 4 June 1996.

The second Cluster mission was launched in two sets of two satellites each on 16 July and 9 August 2000.

Cluster II

The current mission Cluster II is investigating the small-scale structure of 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 have been collecting the most detailed data yet on small-scale changes in near-Earth space and the interaction between the charged particles of the solar wind and Earth's atmosphere. This enables scientists to build a three-dimensional model of the magnetosphere and to better understand the processes taking place inside it. The Cluster mission control centre is located at ESOC, Darmstadt, Germany.

Flight Control Team

B. Sousa

The Flight Control team (FCT) operates Cluster from a Dedicated Control Room located at ESOC, ESA's mission control centre in Darmstadt, Germany.

Spacecraft Operations Manager Bruno Sousa oversees a team of engineers dedicated to the mission, who are supported by an extended 'team of teams' at ESOC. These include specialists from flight dynamics, ground facilities, tracking stations and mission data systems.

The team have done a remarkable job ensuring that the 15-year-old fleet performs all assigned science observations. In 2013, two of the Cluster quartet made their closest-ever approach – just 4 km – and in 2015, satellites 3 and 4 (Samba and Tango) were brought to just 6 km separation in space, to observe activity at Earth's bow shock – the region where the solar wind decelerates from super- to subsonic speeds before being deflected around our planet.

Mission operations overview

Launch and early orbit phase

The first pair of Cluster satellites lifted off on 16 July 2000, the second pair one month later on 9 August 2000. This gap enable a manageable workflow for the mission control team at ESOC.

At launch, each of two Cluster satellites (Salsa and Samba, then Rumba and Tango) were placed in an elliptical orbit whose height varied from 200 to 18 000 km above Earth. The two satellites were released, one after the other, and used their own on-board propulsion systems to reach the final operational orbit (19 000 to 119 000 km from the planet).

Fregat upper stage deploying Cluster

Once the booster reached the correct altitude, after lift off, the Fregat payload assist module and its two Cluster spacecraft were released. The Fregat main engine fired almost immediately to achieve a circular orbit of approximately 200 kilometres high. About an hour later, the Fregat engine fired again to inject the spacecraft into an elliptical orbit.

Each Cluster spacecraft main engine performed six major manoeuvres, using the large amount of on-board fuel (about half of each satellite's launch mass).

VMC image sequence showing Cluster
VMC image sequence showing Cluster's Tango and Rumba separation

Day-to-day operations

One of the most challenging aspects of Cluster is to control four identical spacecraft. The day-to-day operation of the spacecraft is carried out by the European Space Operations Centre (ESOC) in Darmstadt, Germany.

During the two-year mission, signals to and from the spacecraft are sent through ESOC. The centre controls the spacecraft and their payloads, and carries out all activities related to mission planning and scheduling.

Routine ESOC operations are interrupted every six months to conduct orbit manoeuvres. Controllers adjust the separation distances between the four spacecraft in order to allow the study of different scientific phenomena.

The ground station - Maspalomas

Maspalomas S-band and X-band ground station
Maspalomas S-band and X-band ground station

Spacecraft telemetry, command and tracking is carried out primarily by the ESA ground station in Maspalomas, Spain with support of ESTRACK's Perth (Australia), Villafranca (Spain), and New Norcia station.

In the critical early stages between launch and final orbit insertion, additional ground stations in Kourou (French Guiana), Perth (Australia) and Kiruna (Sweden) were used.

Ground segment & mission control system

Cluster ground segment

The Cluster ground segment is used to monitor and control the four satellites, and to receive, archive and distribute the science data. It is composed of the Mission Operations Centre (MOC), ESA's ground station network (ESTRACK), the Cluster Science Data System (CSDS) and the Joint Science Operations Centre (SOC).

The Cluster Mission Control Centre at ESOC is responsible for the:

  • Transfer of the four satellites into their operational orbits and their correct orbital positions
  • Combined operation of the four spacecraft and their payloads
  • Collection and distribution to the scientific community of all the raw science data, as well as monitoring of spacecraft health, orbits, etc.

The vast amount of scientific information sent back by the four spacecraft is handled by CSDS. It supports scientific data processing and distribution activities. SOC coordinates the science operations. Its main task is to merge all commands coming from the 11 instrument teams into an overall command schedule, which is then sent through ESOC to the 44 spacecraft instruments.

The platform and payload

Cutaway diagram of one of the Cluster spacecraft

The platform

The Cluster spacecraft resemble giant 'Lego' sets, assembled by hand from thousands of individual parts. Each one is shaped like a giant disk, 1.3 m high and 2.9 m across. In the centre is a cylinder with an aluminium honeycomb structure covered with a skin of carbon-fibre reinforced plastic. The equipment panel inside this cylinder supports the main engine, two high-pressure fuel tanks and other parts of the propulsion system.

Six spherical fuel tanks made from titanium are attached to the outside of this central cylinder. The fuel they carry accounts for more than half the launch weight of each spacecraft. Most of this fuel was consumed soon after launch, during the complex manoeuvres required to reach their operational orbits. Each spacecraft also carries eight thrusters for smaller changes of orbit.

Cluster
Cluster observes 'magnetic reconnection'
The payload

Each spacecraft carries an identical set of 11 instruments to investigate charged particles, electrical, and magnetic fields. These were built by European and American instrument teams led by Principal Investigators.

The Cluster scientific community includes the ESA Project Scientist, 11 principal investigators, and more than 250 co-investigators from ESA Member States, the United States, Canada, China, the Czech Republic, Hungary, India, Israel, Japan, and Russia.

Instrument

Name

FGM

Fluxgate Magnetometer

EDI

Electron Drift Instrument

ASPOC

Active Spacecraft Potential Control experiment

STAFF

Spatio-Temporal Analysis of Field Fluctuation experiment

FEW

Electric Field and Wave experiment

DWP

Digital Wave Processing experiment

WHISPER

Waves of High Frequency & Sounder for Probing of Electron Density by Relaxation experiment

WBD

Wide Band Data instrument

PEACE

Plasma Electron And Current Experiment

CIS

Cluster Ion Spectrometry experiment

RAPID

Research with Adaptive Particle Imaging Detectors

WEC

Wave Experiment Consortium (WEC)

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