Cluster II (spacecraft)

Cluster II[2] is a space mission of the European Space Agency, with NASA participation, to study the Earth's magnetosphere over the course of nearly two solar cycles. The mission is composed of four identical spacecraft flying in a tetrahedral formation. As a replacement for the original Cluster spacecraft which were lost in a launch failure in 1996, the four Cluster II spacecraft were successfully launched in pairs in July and August 2000 onboard two Soyuz-Fregat rockets from Baikonur, Kazakhstan. In February 2011, Cluster II celebrated 10 years of successful scientific operations in space. In February 2021, Cluster II celebrated 20 years of successful scientific operations in space. As of March 2023, its mission has been extended until September 2024.[3] The China National Space Administration/ESA Double Star mission operated alongside Cluster II from 2004 to 2007.

Cluster II
The Cluster II constellation.
Artist's impression of the Cluster constellation.
Mission typeMagnetospheric research
OperatorESA with NASA collaboration
COSPAR IDFM6 (SALSA): 2000-041A
FM7 (SAMBA): 2000-041B
FM5 (RUMBA): 2000-045A
FM8 (TANGO): 2000-045B
SATCAT no.FM6 (SALSA): 26411
FM7 (SAMBA): 26410
FM5 (RUMBA): 26463
FM8 (TANGO): 26464
Websitehttp://sci.esa.int/cluster
Mission durationPlanned: 5 years
Elasped: 23 years, 10 months and 30 days
Spacecraft properties
ManufacturerAirbus (ex. Dornier)[1]
Launch mass1,200 kg (2,600 lb)[1]
Dry mass550 kg (1,210 lb)[1]
Payload mass71 kg (157 lb)[1]
Dimensions2.9 m × 1.3 m (9.5 ft × 4.3 ft)[1]
Power224 watts[1]
Start of mission
Launch dateFM6: 16 July 2000, 12:39 UTC (2000-07-16UTC12:39Z)
FM7: 16 July 2000, 12:39 UTC (2000-07-16UTC12:39Z)
FM5: 09 August 2000, 11:13 UTC (2000-08-09UTC11:13Z)
FM8: 09 August 2000, 11:13 UTC (2000-08-09UTC11:13Z)
RocketSoyuz-U/Fregat
Launch siteBaikonur 31/6
ContractorStarsem
End of mission
Last contactSeptember 2024 (planned)
Orbital parameters
Reference systemGeocentric
RegimeElliptical Orbit
Perigee altitudeFM6: 16,118 km (10,015 mi)
FM7: 16,157 km (10,039 mi)
FM5: 16,022 km (9,956 mi)
FM8: 12,902 km (8,017 mi)
Apogee altitudeFM6: 116,740 km (72,540 mi)
FM7: 116,654 km (72,485 mi)
FM5: 116,786 km (72,567 mi)
FM8: 119,952 km (74,535 mi)
InclinationFM6: 135 degrees
FM7: 135 degrees
FM5: 138 degrees
FM8: 134 degrees
PeriodFM6: 3259 minutes
FM7: 3257 minutes
FM5: 3257 minutes
FM8: 3258 minutes
Epoch13 March 2014, 11:15:07 UTC
Cluster II mission insignia
ESA solar system insignia for Cluster II 

Mission overview

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The four identical Cluster II satellites study the impact of the Sun's activity on the Earth's space environment by flying in formation around Earth. For the first time in space history, this mission is able to collect three-dimensional information on how the solar wind interacts with the magnetosphere and affects near-Earth space and its atmosphere, including aurorae.

The spacecraft are cylindrical (2.9 x 1.3 m, see online 3D model) and are spinning at 15 rotations per minute. After launch, their solar cells provided 224 watts power for instruments and communications. Solar array power has gradually declined as the mission progressed, due to damage by energetic charged particles, but this was planned for and the power level remains sufficient for science operations. The four spacecraft maneuver into various tetrahedral formations to study the magnetospheric structure and boundaries. The inter-spacecraft distances can be altered and has varied from around 4 to 10,000 km. The propellant for the transfer to the operational orbit, and the maneuvers to vary inter-spacecraft separation distances made up approximately half of the spacecraft's launch weight.

The highly elliptical orbits of the spacecraft initially reached a perigee of around 4 RE (Earth radii, where 1 RE = 6371 km) and an apogee of 19.6 RE. Each orbit took approximately 57 hours to complete. The orbit has evolved over time; the line of apsides has rotated southwards so that the distance at which the orbit crossed the magnetotail current sheet progressively reduced, and a wide range of dayside magnetopause crossing latitudes were sampled. Gravitational effects impose a long term cycle of change in the perigee (and apogee) distance, which saw the perigees reduce to a few 100 km in 2011 before beginning to rise again. The orbit plane has rotated away from 90 degrees inclination. Orbit modifications by ESOC have altered the orbital period to 54 hours. All these changes have allowed Cluster to visit a much wider set of important magnetospheric regions than was possible for the initial 2-year mission, improving the scientific breadth of the mission.

The European Space Operations Centre (ESOC) acquires telemetry and distributes to the online data centers the science data from the spacecraft. The Joint Science Operations Centre JSOC at Rutherford Appleton Laboratory in the UK coordinates scientific planning and in collaboration with the instrument teams provides merged instrument commanding requests to ESOC.

The Cluster Science Archive is the ESA long term archive of the Cluster and Double Star science missions. Since 1 November 2014, it is the sole public access point to the Cluster mission scientific data and supporting datasets. The Double Star data are publicly available via this archive. The Cluster Science Archive is located alongside all the other ESA science archives at the European Space Astronomy Center, located near Madrid, Spain. From February 2006 to October 2014, the Cluster data could be accessed via the Cluster Active Archive.

History

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The Cluster mission was proposed to ESA in 1982 and approved in 1986, along with the Solar and Heliospheric Observatory (SOHO), and together these two missions constituted the Solar Terrestrial Physics "cornerstone" of ESA's Horizon 2000 missions programme. Though the original Cluster spacecraft were completed in 1995, the explosion of the Ariane 5 rocket carrying the satellites in 1996 delayed the mission by four years while new instruments and spacecraft were built.

On July 16, 2000, a Soyuz-Fregat rocket from the Baikonur Cosmodrome launched two of the replacement Cluster II spacecraft, (Salsa and Samba) into a parking orbit from where they maneuvered under their own power into a 19,000 by 119,000 kilometre orbit with a period of 57 hours. Three weeks later on August 9, 2000, another Soyuz-Fregat rocket lifted the remaining two spacecraft (Rumba and Tango) into similar orbits. Spacecraft 1, Rumba, is also known as the Phoenix spacecraft, since it is largely built from spare parts left over after the failure of the original mission. After commissioning of the payload, the first scientific measurements were made on February 1, 2001.

The European Space Agency ran a competition to name the satellites across all of the ESA member states.[4] Ray Cotton, from the United Kingdom, won the competition with the names Rumba, Tango, Salsa and Samba.[5] Ray's town of residence, Bristol, was awarded with scale models of the satellites in recognition of the winning entry,[6][7] as well as the city's connection with the satellites. However, after many years of being stored away, they were finally given a home at the Rutherford Appleton Laboratory.

Originally planned to last until the end of 2003, the mission has been extended several times. The first extension took the mission from 2004 until 2005, and the second from 2005 to June 2009. The mission has now been extended until September 2024.[3]

Scientific objectives

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Previous single and two-spacecraft missions were not capable of providing the data required to accurately study the boundaries of the magnetosphere. Because the plasma comprising the magnetosphere cannot be viewed using remote sensing techniques, satellites must be used to measure it in-situ. Four spacecraft allow scientists make the 3D, time-resolved measurements needed to create a realistic picture of the complex plasma interactions occurring between regions of the magnetosphere and between the magnetosphere and the solar wind.

Each satellite carries a scientific payload of 11 instruments designed to study the small-scale plasma structures in space and time in the key plasma regions: solar wind, bow shock, magnetopause, polar cusps, magnetotail, plasmapause boundary layer and over the polar caps and the auroral zones.

  • The bow shock is the region in space between the Earth and the Sun where the solar wind decelerates from super- to sub-sonic before being deflected around the Earth. In traversing this region, the spacecraft make measurements which help characterize processes occurring at the bow shock, such as the origin of hot flow anomalies and the transmission of electromagnetic waves through the bow shock and the magnetosheath from the solar wind.
  • Behind the bow shock is the thin plasma layer separating the Earth and solar wind magnetic fields known as the magnetopause. This boundary moves continuously due to the constant variation in solar wind pressure. Since the plasma and magnetic pressures within the solar wind and the magnetosphere, respectively, should be in equilibrium, the magnetosphere should be an impenetrable boundary. However, plasma has been observed crossing the magnetopause into the magnetosphere from the solar wind. Cluster's four-point measurements make it possible to track the motion of the magnetopause as well as elucidate the mechanism for plasma penetration from the solar wind.
  • In two regions, one in the northern hemisphere and the other in the south, the magnetic field of the Earth is perpendicular rather than tangential to the magnetopause. These polar cusps allow solar wind particles, consisting of ions and electrons, to flow into the magnetosphere. Cluster records the particle distributions, which allow the turbulent regions at the exterior cusps to be characterized.
  • The regions of the Earth's magnetic field that are stretched by the solar wind away from the Sun are known collectively as the magnetotail. Two lobes that reach past the Moon in length form the outer magnetotail while the central plasma sheet forms the inner magnetotail, which is highly active. Cluster monitors particles from the ionosphere and the solar wind as they pass through the magnetotail lobes. In the central plasma sheet, Cluster determines the origins of ion beams and disruptions to the magnetic field-aligned currents caused by substorms.
  • The precipitation of charged particles in the atmosphere creates a ring of light emission around the magnetic pole known as the auroral zone. Cluster measures the time variations of transient particle flows and electric and magnetic fields in the region.

Instrumentation on each Cluster satellite

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NumberAcronymInstrumentMeasurementPurpose
1ASPOCActive Spacecraft Potential Control experimentRegulation of spacecraft's electrostatic potentialEnables the measure by PEACE of cold electrons (a few eV temperature), otherwise hidden by spacecraft photoelectrons
2CISCluster Ion Spectroscopy experimentIon times-of-flight (TOFs) and energies from 0 to 40 keVComposition and 3D distribution of ions in plasma
3DWPDigital Wave Processing instrumentCoordinates the operations of the EFW, STAFF, WBD and WHISPER instruments.At the lowest level, DWP provides electrical signals to synchronise instrument sampling. At the highest level, DWP enables more complex operational modes by means of macros.
4EDIElectron Drift InstrumentElectric field E magnitude and directionE vector, gradients in local magnetic field B
5EFWElectric Field and Wave experimentElectric field E magnitude and directionE vector, spacecraft potential, electron density and temperature
6FGMFluxgate MagnetometerMagnetic field B magnitude and directionB vector and event trigger to all instruments except ASPOC
7PEACEPlasma Electron and Current ExperimentElectron energies from 0.0007 to 30 keV3D distribution of electrons in plasma
8RAPIDResearch with Adaptive Particle Imaging DetectorsElectron energies from 39 to 406 keV, ion energies from 20 to 450 keV3D distributions of high-energy electrons and ions in plasma
9STAFFSpatio-Temporal Analysis of Field Fluctuation experimentMagnetic field B magnitude and direction of EM fluctuations, cross-correlation of E and BProperties of small-scale current structures, source of plasma waves and turbulence
10WBDWide Band Data receiverHigh time resolution measurements of both electric and magnetic fields in selected frequency bands from 25 Hz to 577 kHz. It provides a unique new capability to perform Very-long-baseline interferometry (VLBI) measurements.Properties of natural plasma waves (e.g. auroral kilometric radiation) in the Earth magnetosphere and its vicinity including: source location and size and propagation.
11WHISPERWaves of High Frequency and Sounder for Probing of Density by RelaxationElectric field E spectrograms of terrestrial plasma waves and radio emissions in the 2–80 kHz range; triggering of plasma resonances by an active sounder.Source location of waves by triangulation; electron density within the range 0.2–80 cm−3

Double Star mission with China

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In 2003 and 2004, the China National Space Administration launched the Double Star satellites, TC-1 and TC-2, that worked together with Cluster to make coordinated measurements mostly within the magnetosphere. TC-1 stopped operating on 14 October 2007. The last data from TC-2 was received in 2008. TC-2 made a contribution to magnetar science[8][9] as well as to magnetospheric physics. The TC-1 examined density holes near the Earth's bow shock that can play a role in bow shock formation[10][11] and looked at neutral sheet oscillations.[12]

Awards

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Cluster team awards

  • 2019Royal Astronomical Society Group Achievement Award[13]
  • 2015ESA 15th anniversary award
  • 2013ESA team award
  • 2010International Academy of Astronautics Laurels for team achievements for Cluster and Double Star teams[14]
  • 2005ESA Cluster 5th anniversary award
  • 2004NASA group achievement award
  • 2000Popular science best of what's new award
  • 2000ESA Cluster launch award

Individual awards

  • 2023 Hermann Opgenoorth (Univ. of Umea, Sweden), former Cluster Ground Based Working Group lead, was awarded the 2023 EGU Julius Bartels Medal[15]
  • 2020 Daniel Graham (Swedish Institute of Space Physics, Uppsala, Sweden) was awarded the COSPAR Zeldovich medal[16]
  • 2019Margaret Kivelson (UCLA, USA), Cluster FGM CoI, received RAS gold medal[17]
  • 2018 Hermann Opgenoorth (Univ. of Umea, Sweden), former Cluster Ground Based Working Group lead, was awarded the 2018 Baron Marcel Nicolet Space Weather and Space Climate medal[18]
  • 2016Stephen Fuselier (SWRI, USA), Cluster CIS CoI, received EGU Hannes Alfvén Meda[19]
  • 2016 Mike Hapgood, Cluster mission scientific operations expert was awarded the Baron Marcel Nicolet Medal for Space Weather and Space Climate[20]
  • 2014Rumi Nakamura (IWF, Austria), Cluster CIS/EDI/FGM CoI, received EGU Julius Bartels Medal[21]
  • 2013Mike Hapgood (RAL, UK), Cluster JSOC project scientist received RAS service award[22]
  • 2013Göran Marklund, EFW Co-I, received the EGU Hannes Alfvén Medal 2013.[23]
  • 2013Steve Milan, Cluster Ground based representative of the Cluster mission received UK Royal Astronomical Society (RAS) Chapman medal[24]
  • 2012Andrew Fazakerley, Cluster and Double Star PI (PEACE), received the Royal Astronomical Society Chapman Medal[25]
  • 2012Zuyin Pu (Pekin U., China), RAPID/CIS/FGM CoI, received AGU International Award[26]
  • 2012Jolene Pickett (Iowa U., USA), a Cluster WBD PI, received the State of Iowa Board of Regents Staff Excellence[27]
  • 2012Jonathan Eastwood (Imperial College, UK), FGM Co-I, received COSPAR Yakov B. Zeldovich medal[28]
  • 2008Andre Balogh (Imperial College, UK), Cluster FGM PI, received RAS Chapman medal[29]
  • 2006Steve Schwartz (QMW, UK), Cluster UK data system scientist and PEACE co-I, received RAS Chapman medal[25]

Discoveries and mission milestones

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2023

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  • April 28 - Magnetic reconnection at high and low latitudes during the passage of an ICME[30]
  • March 24 - Properties of Flapping Current Sheet of the Martian Magnetotail[31]
  • March 23 - Scaling laws for the energy transfer in space plasma turbulence[32]
  • March 01 - Turbulent MHD cascade in the Jovian magnetosheath[33]
  • January 26 - Evidence for lunar tide effects in Earth’s plasmasphere[34]
  • January 20 - Ion Outflow in Middle Altitude LLBL/Cusp from Different Origins[35]

2022

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  • December 05 - Magnetosphere distortions during the “satellite killer” storm of February 3–4, 2022[36]
  • October 14 - New insights on the formation of transpolar auroral arc[37]
  • September 20 - A highway for atmospheric ion escape from Earth during the impact of an interplanetary coronal mass ejection[38]
  • August 03 - Joint Cluster/ground-based studies in the first 20 years of the Cluster mission[39]
  • July 18 – In situ observation of a magnetopause indentation that is correspondent to throat aurora and is caused by magnetopause reconnection[40]
  • June 16 - Kelvin-Helmholtz vortices as an interplay of Magnetosphere-Ionosphere coupling[41]
  • June 02 - ESA highlight: Magnetic vortices explain mysterious auroral beads[42][43]
  • May 16 - The influence of localized dynamics on dusk-dawn convection in the Earth’s magnetotail[44]
  • April 1 - Dawn-dusk ion flow asymmetry in the plasma sheet[45]
  • February 1 - South Pole Station ground-based and Cluster satellite measurements of leaked and escaping Auroral Kilometric Radiation[46]
  • January 1 - Massive multi-mission statistical study and analytical modeling of the Earth's magnetopause[47]

2021

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  • December 15 - ESA highlight: Swarm and Cluster get to the bottom of geomagnetic storms[48][49]
  • November 7 - Unique MMS and Cluster observations about magnetic reconnection extent at the magnetopause[50]
  • November 2 - Spatial distribution of energetic protons in the magnetosphere based on 17 years of data[51]
  • October 11 - Unique MMS and Cluster observation of disturbances in the near-Earth magnetotail before a magnetic substorm[52]
  • September 7 - AGU EOS spotlight: Understanding Aurora Formation with ESA’s Cluster Mission[53]
  • May 2 - Cluster and MMS uncover anisotropic spatial correlation functions at kinetic range in the magnetosheath turbulence[54]
  • April 9 - The Solar-cycle Variations of the Anisotropy of Taylor Scale and Correlation Scale in the Solar Wind Turbulence[55]
  • February 18 - Heavy Metal and Rock in Space: Cluster RAPID Observations of Fe and Si[56]

2020

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  • December 1 - Cluster, Helios and Ulysses reveal characteristics of solar wind supra thermal halo electrons[57]
  • November 1 - Cluster, Swam and CHAMP join forces to explain hemispheric asymmetries in the Earth magnetotail[58]
  • October 21 - Space plasma regimes classified with Cluster data[59]
  • October 1 - Effects of Solar Activity on Taylor Scale and Correlation Scale in Solar Wind Magnetic Fluctuations[60]
  • September 1 - Van Allen Probes and Cluster join forces to study Outer Radiation Belt Electrons[61]
  • August 9 - Cluster’s 20 years of studying Earth’s magnetosphere], celebrating 20 years after the launch of the second pair of Cluster spacecraft[62]
  • July 31 - ESA science highlight: Auroral substorms triggered by short circuiting of plasma flows[63][64]
  • July 16 - BBC skyatnight podcast with Dr. Mike Hapgood on 20 years of ESA’s Cluster mission,[65] celebrating 20 years after the launch of the first pair of Cluster satellites
  • April 20 - What drives some of the largest and most dynamic auroral forms?[66]
  • March 19 - ESA science highlight: Iron is everywhere in Earth's vicinity, suggest two decades of Cluster data[67][68]
  • February 27 - What makes Kelvin Helmholtz vortices grow at the Earth's magnetopause?[69]

2019

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2018

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2017

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2016

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2015

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2014

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2013

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2012

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2011

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2010

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2009

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2008

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2007

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2006

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2005

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2004

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2001–2003

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References

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  • Escoubet, C.P.; A. Masson; H. Laakso; M.L. Goldstein (2021). "Cluster after 20 years of operations: Science highlights and technical challenges". Journal of Geophysical Research: Space Physics. 126 (8). Bibcode:2021JGRA..12629474E. doi:10.1029/2021JA029474. hdl:11603/25562.
  • Escoubet, C.P.; A. Masson; H. Laakso; M.L. Goldstein (2015). "Recent highlights from Cluster, the first 3-D magnetospheric mission". Annales Geophysicae. 33 (10): 1221–1235. Bibcode:2015AnGeo..33.1221E. doi:10.5194/angeo-33-1221-2015. hdl:11603/31311.
  • Escoubet, C.P.; M. Taylor; A. Masson; H. Laakso; J. Volpp; M. Hapgood; M.L. Goldstein (2013). "Dynamical processes in space: Cluster results". Annales Geophysicae. 31 (6): 1045–1059. Bibcode:2013AnGeo..31.1045E. doi:10.5194/angeo-31-1045-2013.
  • Taylor, M.; C.P. Escoubet; H. Laakso; A. Masson; M. Goldstein (2010). "The Cluster Mission: Space Plasma in Three Dimensions". In H. Laakso; et al. (eds.). The Cluster Active Archive. Astrophysics and Space Science Proceedings. Astrophys. & Space Sci. Proc., Springer. pp. 309–330. doi:10.1007/978-90-481-3499-1_21. ISBN 978-90-481-3498-4.
  • Escoubet, C.P.; M. Fehringer; M. Goldstein (2001). "The Cluster mission". Annales Geophysicae. 19 (10/12): 1197–1200. Bibcode:2001AnGeo..19.1197E. doi:10.5194/angeo-19-1197-2001. hdl:11603/30657.
  • Escoubet, C.P.; R. Schmidt; M.L. Goldstein (1997). "Cluster - Science and Mission Overview". Space Science Reviews. 79: 11–32. Bibcode:1997SSRv...79...11E. doi:10.1023/A:1004923124586. hdl:11603/30578. S2CID 116954846.

Selected publications

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All 3721 publications related to the Cluster and the Double Star missions (count as of 31 March 2023) can be found on the publication section of the ESA Cluster mission website. Among these publications, 3228 are refereed publications, 342 proceedings, 121 PhDs and 30 other types of theses.

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