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European Space Agency space mission From Wikipedia, the free encyclopedia
Cluster II[2] was 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 was 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[update], its mission was extended until September 2024.[3] The China National Space Administration/ESA Double Star mission operated alongside Cluster II from 2004 to 2007.
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Artist's impression of the Cluster constellation. | |
| Mission type | Magnetospheric research |
|---|---|
| Operator | ESA with NASA collaboration |
| COSPAR ID | FM6 (SALSA): 2000-041B FM7 (SAMBA): 2000-041A FM5 (RUMBA): 2000-045A FM8 (TANGO): 2000-045B |
| SATCAT no. | FM6 (SALSA): 26411 FM7 (SAMBA): 26410 FM5 (RUMBA): 26463 FM8 (TANGO): 26464 |
| Website | http://sci.esa.int/cluster |
| Mission duration | Planned: 5 years Final: 24 years, 1 month and 6 days |
| Spacecraft properties | |
| Manufacturer | Airbus (ex. Dornier)[1] |
| Launch mass | 1,200 kg (2,600 lb)[1] |
| Dry mass | 550 kg (1,210 lb)[1] |
| Payload mass | 71 kg (157 lb)[1] |
| Dimensions | 2.9 m × 1.3 m (9.5 ft × 4.3 ft)[1] |
| Power | 224 watts[1] |
| Start of mission | |
| Launch date | FM6: 16 July 2000, 12:39 UTC FM7: 16 July 2000, 12:39 UTC FM5: 09 August 2000, 11:13 UTC FM8: 09 August 2000, 11:13 UTC |
| Rocket | Soyuz-U/Fregat |
| Launch site | Baikonur 31/6 |
| Contractor | Starsem |
| End of mission | |
| Last contact | 22 August 2024 |
| Decay date | Salsa: 8 September 2024 |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Elliptical Orbit |
| Perigee altitude | FM6: 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 altitude | FM6: 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) |
| Inclination | FM6: 135 degrees FM7: 135 degrees FM5: 138 degrees FM8: 134 degrees |
| Period | FM6: 3259 minutes FM7: 3257 minutes FM5: 3257 minutes FM8: 3258 minutes |
| Epoch | 13 March 2014, 11:15:07 UTC |
 ESA solar system insignia for Cluster II | |
The first of the satellites of Cluster II to re-enter the atmosphere did so on 8 September 2024. The remaining three are expected to follow in 2025 and 2026.[4] The scientific payload operations of all satellites ended as the first satellite re-entered the atmosphere (other flight operations are still being performed with the remaining flying satellites until the satellites have all re-entered).[5]
The four identical Cluster II satellites studied 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 was 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 were cylindrical (2.9 x 1.3 m, see online 3D model) and were spinning at 15 rotations per minute. After launch, their solar cells provided 224 watts power for instruments and communications. Solar array power 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 maneuvered into various tetrahedral formations to study the magnetospheric structure and boundaries. The inter-spacecraft distances could be altered and 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 evolved over time; the line of apsides 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 imposed 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 rotated away from 90 degrees inclination. Orbit modifications by ESOC altered the orbital period to 54 hours. All these changes 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) acquired telemetry and distributed to the online data centers the science data from the spacecraft. The Joint Science Operations Centre (JSOC) at Rutherford Appleton Laboratory in the UK coordinated scientific planning and in collaboration with the instrument teams provided 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.
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, was 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.[6] Ray Cotton, from the United Kingdom, won the competition with the names Rumba, Tango, Salsa and Samba.[7] Ray's town of residence, Bristol, was awarded with scale models of the satellites in recognition of the winning entry,[8][9] 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 was extended several times. The first extension took the mission from 2004 until 2005, and the second from 2005 to June 2009. The mission was ultimately extended until September 2024, when the scientific payload operations on the satellites ended.[3] The ultimate end of the Cluster project (especially the Cluster II satellites) will happen in 2026 as the last satellite enters the atmosphere and is destroyed.[5]
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 allowed 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 carried 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.
| Number | Acronym | Instrument | Measurement | Purpose |
|---|---|---|---|---|
| 1 | ASPOC | Active Spacecraft Potential Control experiment | Regulation of spacecraft's electrostatic potential | Enabled the measurement by PEACE of cold electrons (a few eV temperature), otherwise hidden by spacecraft photoelectrons |
| 2 | CIS | Cluster Ion Spectroscopy experiment | Ion times-of-flight (TOFs) and energies from 0 to 40 keV | Composition and 3D distribution of ions in plasma |
| 3 | DWP | Digital Wave Processing instrument | Coordinates the operations of the EFW, STAFF, WBD and WHISPER instruments | At the lowest level, DWP provided electrical signals to synchronise instrument sampling. At the highest level, DWP enabled more complex operational modes by means of macros |
| 4 | EDI | Electron Drift Instrument | Electric field E magnitude and direction | E vector, gradients in local magnetic field B |
| 5 | EFW | Electric Field and Wave experiment | Electric field E magnitude and direction | E vector, spacecraft potential, electron density and temperature |
| 6 | FGM | Fluxgate Magnetometer | Magnetic field B magnitude and direction | B vector and event trigger to all instruments except ASPOC |
| 7 | PEACE | Plasma Electron and Current Experiment | Electron energies from 0.0007 to 30 keV | 3D distribution of electrons in plasma |
| 8 | RAPID | Research with Adaptive Particle Imaging Detectors | Electron energies from 39 to 406 keV, ion energies from 20 to 450 keV | 3D distributions of high-energy electrons and ions in plasma |
| 9 | STAFF | Spatio-Temporal Analysis of Field Fluctuation experiment | Magnetic field B magnitude and direction of EM fluctuations, cross-correlation of E and B | Properties of small-scale current structures, source of plasma waves and turbulence |
| 10 | WBD | Wide Band Data receiver | High time resolution measurements of both electric and magnetic fields in selected frequency bands from 25 Hz to 577 kHz. It provided 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 |
| 11 | WHISPER | Waves of High Frequency and Sounder for Probing of Density by Relaxation | Electric 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 |
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[10][11] 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[12][13] and looked at neutral sheet oscillations.[14]
Cluster team awards:
Individual awards:
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